<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019d1bac-b918-7460-844b-4286f2847287,g:19806af6-486c-4542-bb2f-6d1b07e280a8-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodStartLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodStartLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/netLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd#netLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedNetLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedNetLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTerseLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodEndLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodEndLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel"/>
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel"/>
  <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:type="extended">
    <link:label id="lab_us-gaap_SignificantAccountingPoliciesTextBlock_019d1bac-cc86-7ce3-9fa7-1e0819136c1d_terseLabel_en-US" xlink:label="lab_us-gaap_SignificantAccountingPoliciesTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Summary of Significant Accounting Policies</link:label>
    <link:label id="lab_us-gaap_SignificantAccountingPoliciesTextBlock_label_en-US" xlink:label="lab_us-gaap_SignificantAccountingPoliciesTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Significant Accounting Policies [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SignificantAccountingPoliciesTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SignificantAccountingPoliciesTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SignificantAccountingPoliciesTextBlock" xlink:to="lab_us-gaap_SignificantAccountingPoliciesTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CCTTokyoFundingCreditFacilityMember_019d1bac-cc86-798c-976b-bc65a2a3a63e_terseLabel_en-US" xlink:label="lab_fsk_CCTTokyoFundingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">CCT Tokyo Funding Credit Facility</link:label>
    <link:label id="lab_fsk_CCTTokyoFundingCreditFacilityMember_label_en-US" xlink:label="lab_fsk_CCTTokyoFundingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">CCT Tokyo Funding Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_CCTTokyoFundingCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_CCTTokyoFundingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">CCT Tokyo Funding Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CCTTokyoFundingCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_CCTTokyoFundingCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CCTTokyoFundingCreditFacilityMember" xlink:to="lab_fsk_CCTTokyoFundingCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary_019d1bac-cc86-7f69-9d3d-21ac195efc79_terseLabel_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Base (in dollars per share)</link:label>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary_label_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Dividends, Per Share, Declared, Ordinary</link:label>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary_documentation_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Common Stock, Dividends, Per Share, Declared, Ordinary</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:href="fsk-20260331.xsd#fsk_CommonStockDividendsPerShareDeclaredOrdinary"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:to="lab_fsk_CommonStockDividendsPerShareDeclaredOrdinary" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_RangeMember_019d1bac-cbe9-70dc-9cd6-c3ee42fea080_terseLabel_en-US" xlink:label="lab_srt_RangeMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statistical Measurement [Domain]</link:label>
    <link:label id="lab_srt_RangeMember_label_en-US" xlink:label="lab_srt_RangeMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statistical Measurement [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_RangeMember" xlink:to="lab_srt_RangeMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentUnaffiliatedIssuerMember_019d1bac-cc86-777c-a54b-83aee88e12f4_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentUnaffiliatedIssuerMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-controlled/unaffiliated</link:label>
    <link:label id="lab_us-gaap_InvestmentUnaffiliatedIssuerMember_label_en-US" xlink:label="lab_us-gaap_InvestmentUnaffiliatedIssuerMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Unaffiliated Issuer [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentUnaffiliatedIssuerMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentUnaffiliatedIssuerMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentUnaffiliatedIssuerMember" xlink:to="lab_us-gaap_InvestmentUnaffiliatedIssuerMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfShortTermDebtTextBlock_019d1bac-ccf8-731c-b42e-736dc6eb7a27_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfShortTermDebtTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Interest Expense</link:label>
    <link:label id="lab_us-gaap_ScheduleOfShortTermDebtTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfShortTermDebtTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Short-Term Debt [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTextBlock" xlink:to="lab_us-gaap_ScheduleOfShortTermDebtTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_StockRepurchaseProgramMember_019d1bac-ccf8-7239-86ef-13156f85e37e_terseLabel_en-US" xlink:label="lab_fsk_StockRepurchaseProgramMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Repurchase Program</link:label>
    <link:label id="lab_fsk_StockRepurchaseProgramMember_label_en-US" xlink:label="lab_fsk_StockRepurchaseProgramMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Repurchase Program [Member]</link:label>
    <link:label id="lab_fsk_StockRepurchaseProgramMember_documentation_en-US" xlink:label="lab_fsk_StockRepurchaseProgramMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Stock Repurchase Program</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_StockRepurchaseProgramMember" xlink:href="fsk-20260331.xsd#fsk_StockRepurchaseProgramMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_StockRepurchaseProgramMember" xlink:to="lab_fsk_StockRepurchaseProgramMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgPredtrmndFlag_terseLabel_en-US" xlink:label="lab_ecd_AwardTmgPredtrmndFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Timing Predetermined</link:label>
    <link:label id="lab_ecd_AwardTmgPredtrmndFlag_label_en-US" xlink:label="lab_ecd_AwardTmgPredtrmndFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing Predetermined [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgPredtrmndFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgPredtrmndFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgPredtrmndFlag" xlink:to="lab_ecd_AwardTmgPredtrmndFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.65ClassA2NotesOutstandingMember_019d9fda-74f5-709e-9ec7-69f4b7f26922_terseLabel_en-US" xlink:label="lab_fsk_A1.65ClassA2NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.65% Class A-2 Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.65ClassA2NotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.65ClassA2NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.65% Class A-2 Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.65ClassA2NotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.65ClassA2NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.65% Class A-2 Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.65ClassA2NotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.65ClassA2NotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.65ClassA2NotesOutstandingMember" xlink:to="lab_fsk_A1.65ClassA2NotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionAxis_019d1bac-cbe9-74d3-86dc-58c661e9afb3_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Axis]</link:label>
    <link:label id="lab_us-gaap_RelatedPartyTransactionAxis_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis" xlink:to="lab_us-gaap_RelatedPartyTransactionAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold_019d1bac-cc86-710c-825f-b3cab98d27e7_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">(Increase) decrease in receivable for investments sold and repaid</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Receivable for Investment Sold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInReceivableForInvestmentSold"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold" xlink:to="lab_us-gaap_IncreaseDecreaseInReceivableForInvestmentSold" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueByAssetClassAxis_019d1bac-cbe9-7eb7-9fa7-3cdbffcda56a_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueByAssetClassAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Asset Class [Axis]</link:label>
    <link:label id="lab_us-gaap_FairValueByAssetClassAxis_label_en-US" xlink:label="lab_us-gaap_FairValueByAssetClassAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Asset Class [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueByAssetClassAxis" xlink:to="lab_us-gaap_FairValueByAssetClassAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityFileNumber_019d1bac-cc86-7cb7-80e9-2f37a3f6a862_terseLabel_en-US" xlink:label="lab_dei_EntityFileNumber" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity File Number</link:label>
    <link:label id="lab_dei_EntityFileNumber_label_en-US" xlink:label="lab_dei_EntityFileNumber" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Securities Act File Number</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityFileNumber" xlink:to="lab_dei_EntityFileNumber" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax_019d1bac-cc86-7291-8db3-063c23beec63_totalLabel_en-US" xlink:label="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total net realized and unrealized gain (loss)</link:label>
    <link:label id="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax_label_en-US" xlink:label="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Realized And Unrealized Gain (Loss), Investment, Derivative, And Foreign Currency Transaction, Before Tax</link:label>
    <link:label id="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax_documentation_en-US" xlink:label="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Realized And Unrealized Gain (Loss), Investment, Derivative, And Foreign Currency Transaction, Before Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:href="fsk-20260331.xsd#fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:to="lab_fsk_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionBeforeTax" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ValuationTechniqueDomain_019d1bac-cc86-75a7-ad2e-947033be11dc_terseLabel_en-US" xlink:label="lab_us-gaap_ValuationTechniqueDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Valuation Approach and Technique [Domain]</link:label>
    <link:label id="lab_us-gaap_ValuationTechniqueDomain_label_en-US" xlink:label="lab_us-gaap_ValuationTechniqueDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation Approach and Technique [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ValuationTechniqueDomain" xlink:to="lab_us-gaap_ValuationTechniqueDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestRateSwapMember_019d1bac-cbe9-71f4-9ad1-e35ffd9d0ca5_terseLabel_en-US" xlink:label="lab_us-gaap_InterestRateSwapMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap</link:label>
    <link:label id="lab_us-gaap_InterestRateSwapMember_label_en-US" xlink:label="lab_us-gaap_InterestRateSwapMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestRateSwapMember" xlink:to="lab_us-gaap_InterestRateSwapMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TabularListTableTextBlock_terseLabel_en-US" xlink:label="lab_ecd_TabularListTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Tabular List, Table</link:label>
    <link:label id="lab_ecd_TabularListTableTextBlock_label_en-US" xlink:label="lab_ecd_TabularListTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Tabular List [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TabularListTableTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TabularListTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TabularListTableTextBlock" xlink:to="lab_ecd_TabularListTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis_019d1bac-cbe9-7479-8fdb-7a4297ec9019_terseLabel_en-US" xlink:label="lab_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Open Forward Foreign Currency Contract, Identifier [Axis]</link:label>
    <link:label id="lab_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis_label_en-US" xlink:label="lab_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Open Forward Foreign Currency Contract, Identifier [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis" xlink:to="lab_us-gaap_OpenForwardForeignCurrencyContractIdentifierAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_019d1bac-cc86-7764-87cd-93ca9ce7d2fd_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) and unrealized appreciation (depreciation) (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Gain (Loss) on Investment, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:to="lab_us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare_019e1494-0f41-74a9-8ffa-acdfc95bf284_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percent of liquidation preference per share payable in shares</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare_label_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable, Shares, Percent Of Liquidation Preference Per Share</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare_documentation_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable, Shares, Percent Of Liquidation Preference Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:href="fsk-20260331.xsd#fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:to="lab_fsk_PreferredStockDiviendPayableSharesPercentOfLiquidationPreferencePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember_019d1bac-cbe9-74fe-b990-7c7094935976_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly In Arrears Catch-up Threshold</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly In Arrears Catch-up Threshold [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly In Arrears Catch-up Threshold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyInArrearsCatchUpThresholdMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_019d1bac-cc86-71fc-8878-29fa5956f402_terseLabel_en-US" xlink:label="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Recent Accounting Pronouncements</link:label>
    <link:label id="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:to="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.47ClassA1NotesOutstandingMember_019d9f61-2358-7356-b9b8-e09cadd2aa70_terseLabel_en-US" xlink:label="lab_fsk_A1.47ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.47ClassA1NotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.47ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.47ClassA1NotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.47ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.47ClassA1NotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.47ClassA1NotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.47ClassA1NotesOutstandingMember" xlink:to="lab_fsk_A1.47ClassA1NotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SecuredOvernightFinancingRateSofrMember_019d1bac-cc86-7a38-9063-c713130a3873_terseLabel_en-US" xlink:label="lab_us-gaap_SecuredOvernightFinancingRateSofrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Secured Overnight Financing Rate (SOFR)</link:label>
    <link:label id="lab_us-gaap_SecuredOvernightFinancingRateSofrMember_label_en-US" xlink:label="lab_us-gaap_SecuredOvernightFinancingRateSofrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Secured Overnight Financing Rate (SOFR) [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SecuredOvernightFinancingRateSofrMember" xlink:to="lab_us-gaap_SecuredOvernightFinancingRateSofrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_GuaranteeObligationsMaximumExposure_019df2b4-4075-7637-83c1-e910ad355c99_terseLabel_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsMaximumExposure" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Guarantor obligations maximum exposure</link:label>
    <link:label id="lab_us-gaap_GuaranteeObligationsMaximumExposure_label_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsMaximumExposure" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Guarantor Obligations, Maximum Exposure, Undiscounted</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsMaximumExposure" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsMaximumExposure"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_GuaranteeObligationsMaximumExposure" xlink:to="lab_us-gaap_GuaranteeObligationsMaximumExposure" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtSecuritiesMember_019d1bac-cc86-735a-8d2b-cb1ced3c76f4_terseLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded Dent Securities</link:label>
    <link:label id="lab_us-gaap_DebtSecuritiesMember_label_en-US" xlink:label="lab_us-gaap_DebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Securities [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtSecuritiesMember" xlink:to="lab_us-gaap_DebtSecuritiesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract_019d1bac-cbe9-7a7f-a8c5-9518134158dd_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution to Shareholders, Percent Of Total Distributions [Abstract]</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution to Shareholders, Percent Of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:to="lab_fsk_InvestmentCompanyDistributionToShareholdersPercentOfTotalDistributionsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TradingArrByIndTable_terseLabel_en-US" xlink:label="lab_ecd_TradingArrByIndTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Trading Arrangements, by Individual</link:label>
    <link:label id="lab_ecd_TradingArrByIndTable_label_en-US" xlink:label="lab_ecd_TradingArrByIndTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangements, by Individual [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TradingArrByIndTable" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TradingArrByIndTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TradingArrByIndTable" xlink:to="lab_ecd_TradingArrByIndTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyTotalReturnMarketValue_019d1bac-cc86-7fcb-8cde-3a6535599186_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTotalReturnMarketValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total return based on market value</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyTotalReturnMarketValue_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTotalReturnMarketValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Total Return, Market Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTotalReturnMarketValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTotalReturnMarketValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyTotalReturnMarketValue" xlink:to="lab_us-gaap_InvestmentCompanyTotalReturnMarketValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EarningsPerShareBasic_019d1bac-ccf8-7c99-859e-ad74a3b57c41_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerShareBasic" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from operations (Earnings (Losses) per Share) - basic (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_EarningsPerShareBasic_label_en-US" xlink:label="lab_us-gaap_EarningsPerShareBasic" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share, Basic</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EarningsPerShareBasic" xlink:to="lab_us-gaap_EarningsPerShareBasic" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AdjToCompAxis_terseLabel_en-US" xlink:label="lab_ecd_AdjToCompAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustment to Compensation:</link:label>
    <link:label id="lab_ecd_AdjToCompAxis_label_en-US" xlink:label="lab_ecd_AdjToCompAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment to Compensation [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AdjToCompAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AdjToCompAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AdjToCompAxis" xlink:to="lab_ecd_AdjToCompAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionsDisclosureTextBlock_019d1bac-cc86-7339-a1da-d8741912e4b3_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transactions</link:label>
    <link:label id="lab_us-gaap_RelatedPartyTransactionsDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transactions Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:to="lab_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock_019d1bac-cc86-79b0-90d6-8dd886be9547_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Outstanding Financing Arrangements</link:label>
    <link:label id="lab_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Line of Credit Facilities [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock" xlink:to="lab_us-gaap_ScheduleOfLineOfCreditFacilitiesTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NamedExecutiveOfficersFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_NamedExecutiveOfficersFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Named Executive Officers, Footnote</link:label>
    <link:label id="lab_ecd_NamedExecutiveOfficersFnTextBlock_label_en-US" xlink:label="lab_ecd_NamedExecutiveOfficersFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Named Executive Officers, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NamedExecutiveOfficersFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NamedExecutiveOfficersFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NamedExecutiveOfficersFnTextBlock" xlink:to="lab_ecd_NamedExecutiveOfficersFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation_019d1bac-cc86-7750-9043-fc9059f1819b_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized appreciation (depreciation) on unfunded commitments</link:label>
    <link:label id="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation_label_en-US" xlink:label="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Commitment to Investee, Unrealized Appreciation (Depreciation)</link:label>
    <link:label id="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Commitment to Investee, Unrealized Appreciation (Depreciation)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:to="lab_fsk_InvestmentCompanyFinancialCommitmentToInvesteeUnrealizedAppreciationDepreciation" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfStockByClassTable_019d1bac-cbe9-7af2-93a4-f411bf352f67_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock, Class of Stock [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfStockByClassTable_label_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock, Class of Stock [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable" xlink:to="lab_us-gaap_ScheduleOfStockByClassTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_MeasurementInputDiscountRateMember_019d1bac-ccf8-7d29-8a94-75fe1b1c7d60_terseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputDiscountRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Discount Rate</link:label>
    <link:label id="lab_us-gaap_MeasurementInputDiscountRateMember_label_en-US" xlink:label="lab_us-gaap_MeasurementInputDiscountRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measurement Input, Discount Rate [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_MeasurementInputDiscountRateMember" xlink:to="lab_us-gaap_MeasurementInputDiscountRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember_019d1bac-cc86-7b9d-a50c-ec1c82f969fe_terseLabel_en-US" xlink:label="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Real Estate Investment Trusts (REITs)</link:label>
    <link:label id="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember_label_en-US" xlink:label="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Real Estate Investment Trusts (REITs) Sector [Member]</link:label>
    <link:label id="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember_documentation_en-US" xlink:label="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Equity Real Estate Investment Trusts (REITs) Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:href="fsk-20260331.xsd#fsk_EquityRealEstateInvestmentTrustsREITsSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:to="lab_fsk_EquityRealEstateInvestmentTrustsREITsSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis_019d1bac-cc86-75b8-9a62-1f0d0a57134c_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Axis]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis" xlink:to="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_MeasurementInputEbitdaMultipleMember_019d1bac-cc86-71b3-8a2d-21ed1cf3bcf0_terseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputEbitdaMultipleMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">EBITDA Multiple</link:label>
    <link:label id="lab_us-gaap_MeasurementInputEbitdaMultipleMember_label_en-US" xlink:label="lab_us-gaap_MeasurementInputEbitdaMultipleMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measurement Input, EBITDA Multiple [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputEbitdaMultipleMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputEbitdaMultipleMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_MeasurementInputEbitdaMultipleMember" xlink:to="lab_us-gaap_MeasurementInputEbitdaMultipleMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_MeasurementInputTypeDomain_019d1bac-cc86-712a-95da-21d0c61b2858_terseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Measurement Input Type [Domain]</link:label>
    <link:label id="lab_us-gaap_MeasurementInputTypeDomain_label_en-US" xlink:label="lab_us-gaap_MeasurementInputTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measurement Input Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_MeasurementInputTypeDomain" xlink:to="lab_us-gaap_MeasurementInputTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AdjToCompAmt_terseLabel_en-US" xlink:label="lab_ecd_AdjToCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustment to Compensation, Amount</link:label>
    <link:label id="lab_ecd_AdjToCompAmt_label_en-US" xlink:label="lab_ecd_AdjToCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment to Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AdjToCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AdjToCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AdjToCompAmt" xlink:to="lab_ecd_AdjToCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice_019e149f-5020-729f-bc55-c72f6d8cc459_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of trading days that the VWAP exceeds conversion price</link:label>
    <link:label id="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice_label_en-US" xlink:label="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Number Of Consecutive Trading Days Volume Weighted Average Share Price Exceeds Conversion Price</link:label>
    <link:label id="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice_documentation_en-US" xlink:label="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Number Of Consecutive Trading Days Volume Weighted Average Share Price Exceeds Conversion Price</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:href="fsk-20260331.xsd#fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:to="lab_fsk_PreferredStockNumberOfConsecutiveTradingDaysVolumeWeightedAverageSharePriceExceedsConversionPrice" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ConcentrationRiskPercentage1_019d1bac-cc86-7808-864c-e546727dd8e1_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskPercentage1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of&#160;Portfolio</link:label>
    <link:label id="lab_us-gaap_ConcentrationRiskPercentage1_label_en-US" xlink:label="lab_us-gaap_ConcentrationRiskPercentage1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConcentrationRiskPercentage1" xlink:to="lab_us-gaap_ConcentrationRiskPercentage1" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_AffiliatedEntityMember_019d1bac-cc86-7ad4-bb5c-da8fb592fc28_terseLabel_en-US" xlink:label="lab_srt_AffiliatedEntityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">FS/KKR Advisor, LLC</link:label>
    <link:label id="lab_srt_AffiliatedEntityMember_label_en-US" xlink:label="lab_srt_AffiliatedEntityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Affiliated Entity [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_AffiliatedEntityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_AffiliatedEntityMember" xlink:to="lab_srt_AffiliatedEntityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019d1bac-cc86-7103-8c9c-4c5ecdc58b6c_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">The amount of total gains or losses for the period included in changes in net assets attributable to the change in unrealized gains or losses relating to investments still held at the reporting date</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment_019d1bac-cc86-764b-8391-54ee2400bcbe_terseLabel_en-US" xlink:label="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Basis spread on variable rate, credit spread adjustment (as percent)</link:label>
    <link:label id="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment_label_en-US" xlink:label="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Basis Spread On Variable Rate, Credit Spread Adjustment</link:label>
    <link:label id="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment_documentation_en-US" xlink:label="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Instrument, Basis Spread On Variable Rate, Credit Spread Adjustment</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:href="fsk-20260331.xsd#fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:to="lab_fsk_DebtInstrumentBasisSpreadOnVariableRateCreditSpreadAdjustment" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeAssetNotionalAmount_019d1bac-cc86-7617-8fa6-c37b1bc391bb_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeAssetNotionalAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Value at Settlement</link:label>
    <link:label id="lab_us-gaap_DerivativeAssetNotionalAmount_label_en-US" xlink:label="lab_us-gaap_DerivativeAssetNotionalAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Notional Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotionalAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetNotionalAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeAssetNotionalAmount" xlink:to="lab_us-gaap_DerivativeAssetNotionalAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EmployeeStockOptionMember_terseLabel_en-US" xlink:label="lab_us-gaap_EmployeeStockOptionMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Employee Stock Option</link:label>
    <link:label id="lab_us-gaap_EmployeeStockOptionMember_label_en-US" xlink:label="lab_us-gaap_EmployeeStockOptionMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-Based Payment Arrangement, Option [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EmployeeStockOptionMember" xlink:to="lab_us-gaap_EmployeeStockOptionMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgMnpiDiscTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AwardTmgMnpiDiscTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Timing MNPI Disclosure</link:label>
    <link:label id="lab_ecd_AwardTmgMnpiDiscTextBlock_label_en-US" xlink:label="lab_ecd_AwardTmgMnpiDiscTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing MNPI Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgMnpiDiscTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgMnpiDiscTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgMnpiDiscTextBlock" xlink:to="lab_ecd_AwardTmgMnpiDiscTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherGeneralAndAdministrativeExpense_019d1bac-cc86-797f-87bd-ac743f2539a1_terseLabel_en-US" xlink:label="lab_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other general and administrative expenses</link:label>
    <link:label id="lab_us-gaap_OtherGeneralAndAdministrativeExpense_019d1bac-cc86-7e82-897a-e30217adad5a_verboseLabel_en-US" xlink:label="lab_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Other general and administrative expenses</link:label>
    <link:label id="lab_us-gaap_OtherGeneralAndAdministrativeExpense_label_en-US" xlink:label="lab_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other General and Administrative Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:to="lab_us-gaap_OtherGeneralAndAdministrativeExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_019d1bac-cc86-7997-b4c7-8534ce78149f_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio of subordinated income incentive fees to average net assets</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Incentive Fee to Average Net Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:to="lab_us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsPolicyTextBlock_019dd266-37ec-70a6-9a99-5209109a1fd3_terseLabel_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents</link:label>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:to="lab_us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019d1bac-cbe9-7c6f-8fd0-ad774bb7f31c_terseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) on investments:</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019d1bac-cbe9-7b85-92e3-b59ee1d01088_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Net realized (gain) loss on investments</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_019d1bac-cbe9-7055-aa9e-e8d48d84aed1_verboseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net Realized Gain (Loss)</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss_label_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Realized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesRealizedGainLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:to="lab_us-gaap_DebtAndEquitySecuritiesRealizedGainLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InterestRateSwapOneMember_019d1bac-cc86-7140-96b8-997cdebebcc2_terseLabel_en-US" xlink:label="lab_fsk_InterestRateSwapOneMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap One</link:label>
    <link:label id="lab_fsk_InterestRateSwapOneMember_label_en-US" xlink:label="lab_fsk_InterestRateSwapOneMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap One [Member]</link:label>
    <link:label id="lab_fsk_InterestRateSwapOneMember_documentation_en-US" xlink:label="lab_fsk_InterestRateSwapOneMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Swap One</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InterestRateSwapOneMember" xlink:href="fsk-20260331.xsd#fsk_InterestRateSwapOneMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InterestRateSwapOneMember" xlink:to="lab_fsk_InterestRateSwapOneMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees_019d1bac-cbe9-7e16-99f3-e61de20898a4_terseLabel_en-US" xlink:label="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in administrative services expense payable</link:label>
    <link:label id="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees_label_en-US" xlink:label="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) In Accrued Professional Fees</link:label>
    <link:label id="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees_documentation_en-US" xlink:label="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Increase (Decrease) In Accrued Professional Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:href="fsk-20260331.xsd#fsk_IncreaseDecreaseInAccruedProfessionalFees"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:to="lab_fsk_IncreaseDecreaseInAccruedProfessionalFees" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_HealthCareEquipmentServicesSectorMember_019d1bac-cc86-7622-be7f-3ecc3c788055_terseLabel_en-US" xlink:label="lab_fsk_HealthCareEquipmentServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Health Care Equipment &amp; Services</link:label>
    <link:label id="lab_fsk_HealthCareEquipmentServicesSectorMember_label_en-US" xlink:label="lab_fsk_HealthCareEquipmentServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Health Care Equipment &amp; Services Sector [Member]</link:label>
    <link:label id="lab_fsk_HealthCareEquipmentServicesSectorMember_documentation_en-US" xlink:label="lab_fsk_HealthCareEquipmentServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Health Care Equipment &amp; Services Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_HealthCareEquipmentServicesSectorMember" xlink:href="fsk-20260331.xsd#fsk_HealthCareEquipmentServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_HealthCareEquipmentServicesSectorMember" xlink:to="lab_fsk_HealthCareEquipmentServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockholdersEquity_019d1bac-cc86-7e88-a4b8-923a88198ff9_totalLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total stockholders&#8217; equity</link:label>
    <link:label id="lab_us-gaap_StockholdersEquity_019d1bac-cc86-7567-8e26-3a6d52df9884_periodStartLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Net assets at beginning of period</link:label>
    <link:label id="lab_us-gaap_StockholdersEquity_019d1bac-cc86-7b4f-8f3c-abaf2a59707b_periodEndLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Net assets at end of period</link:label>
    <link:label id="lab_us-gaap_StockholdersEquity_019d1bac-cc86-7541-b514-f8a7d5cdafe7_verboseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Member&#8217;s equity</link:label>
    <link:label id="lab_us-gaap_StockholdersEquity_019d1bac-cc86-78a7-9518-39fa343262e3_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net assets, end of period</link:label>
    <link:label id="lab_us-gaap_StockholdersEquity_label_en-US" xlink:label="lab_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity, Attributable to Parent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockholdersEquity" xlink:to="lab_us-gaap_StockholdersEquity" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeInstrumentsGainLossLineItems_019d1bac-cc86-7352-bbc4-7f867681451f_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Instruments, Gain (Loss) [Line Items]</link:label>
    <link:label id="lab_us-gaap_DerivativeInstrumentsGainLossLineItems_label_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instruments, Gain (Loss) [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:to="lab_us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionOrdinaryIncome_019d1bac-ccf8-7be2-8d24-8bcb367eb67f_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionOrdinaryIncome" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net investment income</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionOrdinaryIncome_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionOrdinaryIncome" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Ordinary Income</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionOrdinaryIncome" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributionOrdinaryIncome"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributionOrdinaryIncome" xlink:to="lab_us-gaap_InvestmentCompanyDistributionOrdinaryIncome" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_InsiderTradingPoliciesProcLineItems_label_en-US" xlink:label="lab_ecd_InsiderTradingPoliciesProcLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Insider Trading Policies and Procedures [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_InsiderTradingPoliciesProcLineItems" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_InsiderTradingPoliciesProcLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_InsiderTradingPoliciesProcLineItems" xlink:to="lab_ecd_InsiderTradingPoliciesProcLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockSharesAuthorized_019d1bac-cc86-7f7e-8425-146349e9abff_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common stock, shares authorized (in shares)</link:label>
    <link:label id="lab_us-gaap_CommonStockSharesAuthorized_label_en-US" xlink:label="lab_us-gaap_CommonStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Shares Authorized</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockSharesAuthorized" xlink:to="lab_us-gaap_CommonStockSharesAuthorized" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_019d1bac-cc86-7667-9a96-5a0b3738c12d_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from operations (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Investment Income (Loss) from Operations, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:to="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock_019d1bac-cc86-71e2-ab58-ef39000764ee_terseLabel_en-US" xlink:label="lab_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Distributions</link:label>
    <link:label id="lab_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock_label_en-US" xlink:label="lab_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Distribution of Assets, Liabilities and Stockholders' Equity [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock" xlink:to="lab_srt_DistributionOfAssetsLiabilitiesAndStockholdersEquityTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember_019d1bac-cc86-774c-a550-827a093c611e_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Catch-Up Threshold</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Catch-Up Threshold [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Catch-Up Threshold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LiabilitiesAndStockholdersEquity_019d1bac-cc86-7cce-afa0-5ed8f70bb693_totalLabel_en-US" xlink:label="lab_us-gaap_LiabilitiesAndStockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total liabilities and stockholders&#8217; equity</link:label>
    <link:label id="lab_us-gaap_LiabilitiesAndStockholdersEquity_label_en-US" xlink:label="lab_us-gaap_LiabilitiesAndStockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liabilities and Equity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="lab_us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019d1bac-cc86-7e99-8471-4a3d274dbe0a_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Instruments, Gain (Loss) [Table]</link:label>
    <link:label id="lab_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_label_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instruments, Gain (Loss) [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:to="lab_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ConcentrationRiskByBenchmarkAxis_019d1bac-cc86-778f-b7fb-5b1e89c73b98_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Axis]</link:label>
    <link:label id="lab_us-gaap_ConcentrationRiskByBenchmarkAxis_label_en-US" xlink:label="lab_us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="lab_us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_CoverAbstract_label_en-US" xlink:label="lab_dei_CoverAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cover [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_CoverAbstract" xlink:to="lab_dei_CoverAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.48ClassA1LNotesOutstandingMember_019d1bac-ccf8-7587-a5ee-c9ada582760c_terseLabel_en-US" xlink:label="lab_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.48% Class A-1L Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.48ClassA1LNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.48% Class A-1L Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.48ClassA1LNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.48% Class A-1L Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.48ClassA1LNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:to="lab_fsk_A1.48ClassA1LNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_MaximumMember_019d1bac-cc86-7ceb-bacf-83250a05d0fb_terseLabel_en-US" xlink:label="lab_srt_MaximumMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maximum</link:label>
    <link:label id="lab_srt_MaximumMember_label_en-US" xlink:label="lab_srt_MaximumMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Maximum [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_MaximumMember" xlink:to="lab_srt_MaximumMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest_019d1bac-cc86-79e0-b17b-fa0fc18bcd17_terseLabel_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Paid-in-kind interest</link:label>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest_label_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Paid-In-Kind Interest</link:label>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest_documentation_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Paid-In-Kind Interest</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:href="fsk-20260331.xsd#fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:to="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisPaidInKindInterest" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ValuationIndicativeDealerQuotesApproachMember_019d1bac-cc86-7f08-8b13-21cd90dde6fd_terseLabel_en-US" xlink:label="lab_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Indicative Dealer Quotes</link:label>
    <link:label id="lab_fsk_ValuationIndicativeDealerQuotesApproachMember_label_en-US" xlink:label="lab_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation, Indicative Dealer Quotes Approach [Member]</link:label>
    <link:label id="lab_fsk_ValuationIndicativeDealerQuotesApproachMember_documentation_en-US" xlink:label="lab_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Valuation, Indicative Dealer Quotes Approach [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:href="fsk-20260331.xsd#fsk_ValuationIndicativeDealerQuotesApproachMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:to="lab_fsk_ValuationIndicativeDealerQuotesApproachMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeCollateralObligationToReturnSecurities_019d1bac-ccf8-765c-9248-39adb4526c01_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DerivativeCollateralObligationToReturnSecurities" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Non-cash Collateral Received</link:label>
    <link:label id="lab_us-gaap_DerivativeCollateralObligationToReturnSecurities_label_en-US" xlink:label="lab_us-gaap_DerivativeCollateralObligationToReturnSecurities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Security Not Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralObligationToReturnSecurities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeCollateralObligationToReturnSecurities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeCollateralObligationToReturnSecurities" xlink:to="lab_us-gaap_DerivativeCollateralObligationToReturnSecurities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AccountingPoliciesAbstract_label_en-US" xlink:label="lab_us-gaap_AccountingPoliciesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Policies [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingPoliciesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountingPoliciesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AccountingPoliciesAbstract" xlink:to="lab_us-gaap_AccountingPoliciesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ConcentrationRiskTypeDomain_019d1bac-cc86-747d-8e20-d4407a4c898f_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Domain]</link:label>
    <link:label id="lab_us-gaap_ConcentrationRiskTypeDomain_label_en-US" xlink:label="lab_us-gaap_ConcentrationRiskTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain" xlink:to="lab_us-gaap_ConcentrationRiskTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonPeoNeoAvgTotalCompAmt_terseLabel_en-US" xlink:label="lab_ecd_NonPeoNeoAvgTotalCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-PEO NEO Average Total Compensation Amount</link:label>
    <link:label id="lab_ecd_NonPeoNeoAvgTotalCompAmt_label_en-US" xlink:label="lab_ecd_NonPeoNeoAvgTotalCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-PEO NEO Average Total Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonPeoNeoAvgTotalCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonPeoNeoAvgTotalCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonPeoNeoAvgTotalCompAmt" xlink:to="lab_ecd_NonPeoNeoAvgTotalCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentLineItems_019d1bac-cc86-757d-960b-033af9c77972_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument [Line Items]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentLineItems_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentLineItems" xlink:to="lab_us-gaap_DebtInstrumentLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncentiveFeePayable_019d1bac-cbe9-72aa-ac32-892bc503726e_verboseLabel_en-US" xlink:label="lab_us-gaap_IncentiveFeePayable" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Subordinated income incentive fees payable</link:label>
    <link:label id="lab_us-gaap_IncentiveFeePayable_019d1bac-cbe9-7541-8525-500e7942aa68_terseLabel_en-US" xlink:label="lab_us-gaap_IncentiveFeePayable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subordinated income incentive fees payable</link:label>
    <link:label id="lab_us-gaap_IncentiveFeePayable_label_en-US" xlink:label="lab_us-gaap_IncentiveFeePayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Incentive Fee Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncentiveFeePayable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncentiveFeePayable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncentiveFeePayable" xlink:to="lab_us-gaap_IncentiveFeePayable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentIdentifierAxis_019d1bac-cc86-7049-b96b-1927d7a54307_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentIdentifierAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment, Identifier [Axis]</link:label>
    <link:label id="lab_us-gaap_InvestmentIdentifierAxis_label_en-US" xlink:label="lab_us-gaap_InvestmentIdentifierAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Identifier [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIdentifierAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIdentifierAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentIdentifierAxis" xlink:to="lab_us-gaap_InvestmentIdentifierAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashNotHeldInForeignCurrency_019d1bac-cbe9-7877-8129-8e2e45706ab0_terseLabel_en-US" xlink:label="lab_us-gaap_CashNotHeldInForeignCurrency" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents</link:label>
    <link:label id="lab_us-gaap_CashNotHeldInForeignCurrency_label_en-US" xlink:label="lab_us-gaap_CashNotHeldInForeignCurrency" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalent, Not Held in Foreign Currency</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashNotHeldInForeignCurrency" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashNotHeldInForeignCurrency"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashNotHeldInForeignCurrency" xlink:to="lab_us-gaap_CashNotHeldInForeignCurrency" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AdjToNonPeoNeoCompFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AdjToNonPeoNeoCompFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustment to Non-PEO NEO Compensation Footnote</link:label>
    <link:label id="lab_ecd_AdjToNonPeoNeoCompFnTextBlock_label_en-US" xlink:label="lab_ecd_AdjToNonPeoNeoCompFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment to Non-PEO NEO Compensation Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AdjToNonPeoNeoCompFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AdjToNonPeoNeoCompFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AdjToNonPeoNeoCompFnTextBlock" xlink:to="lab_ecd_AdjToNonPeoNeoCompFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PayVsPerformanceDisclosureLineItems_label_en-US" xlink:label="lab_ecd_PayVsPerformanceDisclosureLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pay vs Performance Disclosure [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PayVsPerformanceDisclosureLineItems" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PayVsPerformanceDisclosureLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PayVsPerformanceDisclosureLineItems" xlink:to="lab_ecd_PayVsPerformanceDisclosureLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtLongtermAndShorttermCombinedAmount_019d1bac-cc86-7688-9ea6-ace18d5ea6d3_terseLabel_en-US" xlink:label="lab_us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt</link:label>
    <link:label id="lab_us-gaap_DebtLongtermAndShorttermCombinedAmount_label_en-US" xlink:label="lab_us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt, Long-Term and Short-Term, Combined Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:to="lab_us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentOwnedAtFairValue_019d1bac-cc86-7112-b848-2f5ad23a0e4f_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Investments, at fair value</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtFairValue_019d1bac-cc86-7346-974b-ebebfba708fb_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtFairValue_019d1bac-cc86-73de-9069-142a2538819f_periodStartLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Fair Value, beginning balance</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtFairValue_019d1bac-cc86-748a-ba42-bb326a5c0a0f_periodEndLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Fair Value, ending balance</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtFairValue_label_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, Fair Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentOwnedAtFairValue" xlink:to="lab_us-gaap_InvestmentOwnedAtFairValue" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt_terseLabel_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Disqualification of Tax Benefits, Amount</link:label>
    <link:label id="lab_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt_label_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Disqualification of Tax Benefits, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt" xlink:to="lab_ecd_ForgoneRecoveryDueToDisqualificationOfTaxBenefitsAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease_019d1bac-cc86-7a29-9cef-9f5aabf0fcb4_negatedTotalLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:type="resource" xml:lang="en-US">Net decrease in net assets resulting from stockholder distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Dividend Distribution, Increase (Decrease)</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Dividend Distribution, Increase (Decrease)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDividendDistributionIncreaseDecrease"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:to="lab_fsk_InvestmentCompanyDividendDistributionIncreaseDecrease" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentAffiliatedIssuerControlledMember_019d1bac-cc86-73e4-82fa-7ec74f1b091e_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Controlled/affiliated</link:label>
    <link:label id="lab_us-gaap_InvestmentAffiliatedIssuerControlledMember_label_en-US" xlink:label="lab_us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Affiliated Issuer, Controlled [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:to="lab_us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockLiquidationPreference_019e1490-75e0-79d1-95bd-94927d6f8f24_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockLiquidationPreference" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Liquidation preference (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_PreferredStockLiquidationPreference_label_en-US" xlink:label="lab_us-gaap_PreferredStockLiquidationPreference" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Liquidation Preference Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreference" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockLiquidationPreference"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockLiquidationPreference" xlink:to="lab_us-gaap_PreferredStockLiquidationPreference" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions_019d1bac-cbe9-745d-aa86-7b639af0c418_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term capital gains proceeds from the sale of assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Long-Term Capital Gain, Percent Of Total Distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Long-Term Capital Gain, Percent Of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:to="lab_fsk_InvestmentCompanyDistributionLongTermCapitalGainPercentOfTotalDistributions" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LiabilitiesAbstract_019d1bac-cbe9-7194-baa8-6c405d065d57_terseLabel_en-US" xlink:label="lab_us-gaap_LiabilitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Liabilities</link:label>
    <link:label id="lab_us-gaap_LiabilitiesAbstract_label_en-US" xlink:label="lab_us-gaap_LiabilitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liabilities [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LiabilitiesAbstract" xlink:to="lab_us-gaap_LiabilitiesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonRule10b51ArrTrmntdFlag_terseLabel_en-US" xlink:label="lab_ecd_NonRule10b51ArrTrmntdFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-Rule 10b5-1 Arrangement Terminated</link:label>
    <link:label id="lab_ecd_NonRule10b51ArrTrmntdFlag_label_en-US" xlink:label="lab_ecd_NonRule10b51ArrTrmntdFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-Rule 10b5-1 Arrangement Terminated [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonRule10b51ArrTrmntdFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonRule10b51ArrTrmntdFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonRule10b51ArrTrmntdFlag" xlink:to="lab_ecd_NonRule10b51ArrTrmntdFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentVariableRate_019d1bac-ccf8-7823-99da-e7f448f74d0a_terseLabel_en-US" xlink:label="lab_fsk_InvestmentVariableRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable rate</link:label>
    <link:label id="lab_fsk_InvestmentVariableRate_label_en-US" xlink:label="lab_fsk_InvestmentVariableRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Variable Rate</link:label>
    <link:label id="lab_fsk_InvestmentVariableRate_documentation_en-US" xlink:label="lab_fsk_InvestmentVariableRate" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment, Variable Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentVariableRate" xlink:href="fsk-20260331.xsd#fsk_InvestmentVariableRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentVariableRate" xlink:to="lab_fsk_InvestmentVariableRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PayableInvestmentPurchase_019d1bac-cc86-7872-8d69-72bf5d632d35_terseLabel_en-US" xlink:label="lab_us-gaap_PayableInvestmentPurchase" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Payable for investments purchased</link:label>
    <link:label id="lab_us-gaap_PayableInvestmentPurchase_label_en-US" xlink:label="lab_us-gaap_PayableInvestmentPurchase" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payable, Investment, Purchase</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PayableInvestmentPurchase" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PayableInvestmentPurchase"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PayableInvestmentPurchase" xlink:to="lab_us-gaap_PayableInvestmentPurchase" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityShellCompany_019d1bac-cc86-71b1-bd06-d2f9ade10f11_terseLabel_en-US" xlink:label="lab_dei_EntityShellCompany" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Shell Company</link:label>
    <link:label id="lab_dei_EntityShellCompany_label_en-US" xlink:label="lab_dei_EntityShellCompany" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Shell Company</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityShellCompany" xlink:to="lab_dei_EntityShellCompany" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock_019d1bac-cbe9-7f7c-8ec3-05d2efa20bc2_terseLabel_en-US" xlink:label="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Unfunded Commitments</link:label>
    <link:label id="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock_label_en-US" xlink:label="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule For Financial Support For Nonconsolidated Entity [Table Text Block]</link:label>
    <link:label id="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock_documentation_en-US" xlink:label="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule For Financial Support For Nonconsolidated Entity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:href="fsk-20260331.xsd#fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:to="lab_fsk_ScheduleForFinancialSupportForNonconsolidatedEntityTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongTermDebtAverageAmountOutstanding_019d1bac-cc86-7d9f-a6a2-ed6fcdb9ca58_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebtAverageAmountOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average outstanding amount</link:label>
    <link:label id="lab_us-gaap_LongTermDebtAverageAmountOutstanding_label_en-US" xlink:label="lab_us-gaap_LongTermDebtAverageAmountOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Average Amount Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAverageAmountOutstanding" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAverageAmountOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebtAverageAmountOutstanding" xlink:to="lab_us-gaap_LongTermDebtAverageAmountOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentTable_019d1bac-cbe9-7469-9ed9-659bdd8d1ba2_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Long-Term Debt Instruments [Table]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentTable_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Long-Term Debt Instruments [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentTable" xlink:to="lab_us-gaap_DebtInstrumentTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersAxis_019d1bac-cc86-7034-bfa3-356f61c3cf64_terseLabel_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders [Axis]</link:label>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersAxis_label_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders [Axis]</link:label>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersAxis_documentation_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersAxis" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_BorrowingsTypeOfLendersAxis" xlink:href="fsk-20260331.xsd#fsk_BorrowingsTypeOfLendersAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_BorrowingsTypeOfLendersAxis" xlink:to="lab_fsk_BorrowingsTypeOfLendersAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019d1bac-cc86-7e5f-9681-c36a658ade8c_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StatementOfStockholdersEquityAbstract_label_en-US" xlink:label="lab_us-gaap_StatementOfStockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Stockholders' Equity [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfStockholdersEquityAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementOfStockholdersEquityAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="lab_us-gaap_StatementOfStockholdersEquityAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber_019e14b1-a8c8-7353-884c-58fbbe32aa28_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of board members a shareholder of convertible preferred stock has a right to elect</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber_label_en-US" xlink:label="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Right To Elect Members Of The Board, Number</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber_documentation_en-US" xlink:label="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Right To Elect Members Of The Board, Number</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:href="fsk-20260331.xsd#fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:to="lab_fsk_PreferredStockConvertibleRightToElectMembersOfTheBoardNumber" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable_019d1bac-cbe9-72b8-8b44-b9c160f01542_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">(Increase) decrease in income receivable</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Interest and Dividends Receivable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable" xlink:to="lab_us-gaap_IncreaseDecreaseInInterestAndDividendsReceivable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees_019d1bac-cc86-7362-a4ef-3b21f610f115_terseLabel_en-US" xlink:label="lab_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Custodian and accounting fees</link:label>
    <link:label id="lab_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees_label_en-US" xlink:label="lab_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Transfer Agent and Custodian Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestExpenseTransferAgentAndCustodianFees"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees" xlink:to="lab_us-gaap_NoninterestExpenseTransferAgentAndCustodianFees" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StatementOfCashFlowsAbstract_label_en-US" xlink:label="lab_us-gaap_StatementOfCashFlowsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Cash Flows [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementOfCashFlowsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:to="lab_us-gaap_StatementOfCashFlowsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CoSelectedMeasureAmt_terseLabel_en-US" xlink:label="lab_ecd_CoSelectedMeasureAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Company Selected Measure Amount</link:label>
    <link:label id="lab_ecd_CoSelectedMeasureAmt_label_en-US" xlink:label="lab_ecd_CoSelectedMeasureAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Company Selected Measure Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CoSelectedMeasureAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CoSelectedMeasureAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CoSelectedMeasureAmt" xlink:to="lab_ecd_CoSelectedMeasureAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgMnpiCnsdrdFlag_terseLabel_en-US" xlink:label="lab_ecd_AwardTmgMnpiCnsdrdFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Timing MNPI Considered</link:label>
    <link:label id="lab_ecd_AwardTmgMnpiCnsdrdFlag_label_en-US" xlink:label="lab_ecd_AwardTmgMnpiCnsdrdFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing MNPI Considered [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgMnpiCnsdrdFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgMnpiCnsdrdFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgMnpiCnsdrdFlag" xlink:to="lab_ecd_AwardTmgMnpiCnsdrdFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestExpenseOperating_019d1bac-cc86-7abb-901d-3e676f486bb5_terseLabel_en-US" xlink:label="lab_us-gaap_InterestExpenseOperating" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest expense</link:label>
    <link:label id="lab_us-gaap_InterestExpenseOperating_label_en-US" xlink:label="lab_us-gaap_InterestExpenseOperating" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Expense, Operating</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOperating" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseOperating"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestExpenseOperating" xlink:to="lab_us-gaap_InterestExpenseOperating" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember_019d1bac-cc86-7f47-954d-38fb43071a22_terseLabel_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Greater Than Or Equal To</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember_label_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Greater Than Or Equal To [Member]</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember_documentation_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Greater Than Or Equal To</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:href="fsk-20260331.xsd#fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:to="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkGreaterThanOrEqualToMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_MeasurementInputTypeAxis_019d1bac-cc86-70f0-a081-d8f5bc7ee52a_terseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Measurement Input Type [Axis]</link:label>
    <link:label id="lab_us-gaap_MeasurementInputTypeAxis_label_en-US" xlink:label="lab_us-gaap_MeasurementInputTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measurement Input Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_MeasurementInputTypeAxis" xlink:to="lab_us-gaap_MeasurementInputTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember_019d1bac-cc86-7295-9926-9c0c11e708ab_terseLabel_en-US" xlink:label="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Illiquidity Discount</link:label>
    <link:label id="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember_label_en-US" xlink:label="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measurement Input, Equity Illiquidity Discount [Member]</link:label>
    <link:label id="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember_documentation_en-US" xlink:label="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Measurement Input, Equity Illiquidity Discount [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:href="fsk-20260331.xsd#fsk_MeasurementInputEquityIlliquidityDiscountMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:to="lab_fsk_MeasurementInputEquityIlliquidityDiscountMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ConsumerServicesSectorMember_019d1bac-cc86-730a-8e83-3806d03aa1ee_terseLabel_en-US" xlink:label="lab_fsk_ConsumerServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consumer Services</link:label>
    <link:label id="lab_fsk_ConsumerServicesSectorMember_label_en-US" xlink:label="lab_fsk_ConsumerServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consumer Services Sector [Member]</link:label>
    <link:label id="lab_fsk_ConsumerServicesSectorMember_documentation_en-US" xlink:label="lab_fsk_ConsumerServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Consumer Services Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ConsumerServicesSectorMember" xlink:href="fsk-20260331.xsd#fsk_ConsumerServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ConsumerServicesSectorMember" xlink:to="lab_fsk_ConsumerServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentIssuerAffiliationAxis_019d1bac-cc86-70c9-a267-ad6e8379b091_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentIssuerAffiliationAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment, Issuer Affiliation [Axis]</link:label>
    <link:label id="lab_us-gaap_InvestmentIssuerAffiliationAxis_label_en-US" xlink:label="lab_us-gaap_InvestmentIssuerAffiliationAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Issuer Affiliation [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIssuerAffiliationAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIssuerAffiliationAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="lab_us-gaap_InvestmentIssuerAffiliationAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_MeasureName_terseLabel_en-US" xlink:label="lab_ecd_MeasureName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Name</link:label>
    <link:label id="lab_ecd_MeasureName_label_en-US" xlink:label="lab_ecd_MeasureName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measure Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_MeasureName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_MeasureName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_MeasureName" xlink:to="lab_ecd_MeasureName" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LetterOfCreditMember_019d1bac-ccf8-723b-a159-c694c09ffece_terseLabel_en-US" xlink:label="lab_us-gaap_LetterOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Letter of Credit</link:label>
    <link:label id="lab_us-gaap_LetterOfCreditMember_label_en-US" xlink:label="lab_us-gaap_LetterOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Letter of Credit [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LetterOfCreditMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LetterOfCreditMember" xlink:to="lab_us-gaap_LetterOfCreditMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CallowhillCreditFacilityMember_019d1bac-cc86-7886-bbf9-3d4ca6198cd4_terseLabel_en-US" xlink:label="lab_fsk_CallowhillCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Callowhill Credit Facility</link:label>
    <link:label id="lab_fsk_CallowhillCreditFacilityMember_label_en-US" xlink:label="lab_fsk_CallowhillCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Callowhill Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_CallowhillCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_CallowhillCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Callowhill Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CallowhillCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_CallowhillCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CallowhillCreditFacilityMember" xlink:to="lab_fsk_CallowhillCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_IndustryConcentrationRiskMember_019d1bac-cbe9-7f94-be9b-920e15cc09e3_terseLabel_en-US" xlink:label="lab_fsk_IndustryConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Industry Concentration Risk</link:label>
    <link:label id="lab_fsk_IndustryConcentrationRiskMember_label_en-US" xlink:label="lab_fsk_IndustryConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Industry Concentration Risk [Member]</link:label>
    <link:label id="lab_fsk_IndustryConcentrationRiskMember_documentation_en-US" xlink:label="lab_fsk_IndustryConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Industry Concentration Risk</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_IndustryConcentrationRiskMember" xlink:href="fsk-20260331.xsd#fsk_IndustryConcentrationRiskMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_IndustryConcentrationRiskMember" xlink:to="lab_fsk_IndustryConcentrationRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost_019d1bac-ccf8-7f7c-a175-5efc439e4d0d_terseLabel_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Allocation of costs of administrative personnel for services rendered</link:label>
    <link:label id="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost_label_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Administrative Fee Expense, Allocation Of Administrative Cost</link:label>
    <link:label id="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost_documentation_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Administrative Fee Expense, Allocation Of Administrative Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:href="fsk-20260331.xsd#fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:to="lab_fsk_AdministrativeFeeExpenseAllocationOfAdministrativeCost" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross_019d1bac-cbe9-7962-bd4a-f067c3ec398f_terseLabel_en-US" xlink:label="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross deferred tax liability</link:label>
    <link:label id="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross_label_en-US" xlink:label="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Tax Liabilities, Investments, Gross</link:label>
    <link:label id="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross_documentation_en-US" xlink:label="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Deferred Tax Liabilities, Investments, Gross</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:href="fsk-20260331.xsd#fsk_DeferredTaxLiabilitiesInvestmentsGross"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:to="lab_fsk_DeferredTaxLiabilitiesInvestmentsGross" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ManagementFeeExpense_019d1bac-cc86-7fe8-afec-271f9ddec59d_terseLabel_en-US" xlink:label="lab_us-gaap_ManagementFeeExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Management fees</link:label>
    <link:label id="lab_us-gaap_ManagementFeeExpense_019d1bac-cc86-7462-942a-ae324f4704f0_verboseLabel_en-US" xlink:label="lab_us-gaap_ManagementFeeExpense" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Base Management Fee</link:label>
    <link:label id="lab_us-gaap_ManagementFeeExpense_label_en-US" xlink:label="lab_us-gaap_ManagementFeeExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Management Fee Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementFeeExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementFeeExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ManagementFeeExpense" xlink:to="lab_us-gaap_ManagementFeeExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ConsumerStaplesDistributionRetailSectorMember_019d1bac-cc86-7a4e-8a3b-93320079cdd5_terseLabel_en-US" xlink:label="lab_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consumer Staples Distribution &amp; Retail</link:label>
    <link:label id="lab_fsk_ConsumerStaplesDistributionRetailSectorMember_label_en-US" xlink:label="lab_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consumer Staples Distribution &amp; Retail Sector [Member]</link:label>
    <link:label id="lab_fsk_ConsumerStaplesDistributionRetailSectorMember_documentation_en-US" xlink:label="lab_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Consumer Staples Distribution &amp; Retail Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:href="fsk-20260331.xsd#fsk_ConsumerStaplesDistributionRetailSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:to="lab_fsk_ConsumerStaplesDistributionRetailSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtInstrumentVariableRateFloor_019d1bac-ccf8-79d0-b8bd-42aee1698e66_terseLabel_en-US" xlink:label="lab_fsk_DebtInstrumentVariableRateFloor" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Floor on benchmark rate (as percent)</link:label>
    <link:label id="lab_fsk_DebtInstrumentVariableRateFloor_label_en-US" xlink:label="lab_fsk_DebtInstrumentVariableRateFloor" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Variable Rate, Floor</link:label>
    <link:label id="lab_fsk_DebtInstrumentVariableRateFloor_documentation_en-US" xlink:label="lab_fsk_DebtInstrumentVariableRateFloor" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Instrument, Variable Rate, Floor</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtInstrumentVariableRateFloor" xlink:href="fsk-20260331.xsd#fsk_DebtInstrumentVariableRateFloor"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtInstrumentVariableRateFloor" xlink:to="lab_fsk_DebtInstrumentVariableRateFloor" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EquitySecuritiesIndustryMember_019d1bac-cc86-7cb3-b766-36a48f1f2b27_terseLabel_en-US" xlink:label="lab_us-gaap_EquitySecuritiesIndustryMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Industry Sector [Domain]</link:label>
    <link:label id="lab_us-gaap_EquitySecuritiesIndustryMember_label_en-US" xlink:label="lab_us-gaap_EquitySecuritiesIndustryMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Industry Sector [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesIndustryMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesIndustryMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember" xlink:to="lab_us-gaap_EquitySecuritiesIndustryMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ClassOfStockLineItems_019d1bac-cc86-76b6-aa7d-dc44e3bf061b_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfStockLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Class of Stock [Line Items]</link:label>
    <link:label id="lab_us-gaap_ClassOfStockLineItems_label_en-US" xlink:label="lab_us-gaap_ClassOfStockLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Stock [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ClassOfStockLineItems" xlink:to="lab_us-gaap_ClassOfStockLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ConsumerDurablesApparelSectorMember_019d1bac-cc86-724f-a547-5bad56438ba4_terseLabel_en-US" xlink:label="lab_fsk_ConsumerDurablesApparelSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consumer Durables &amp; Apparel</link:label>
    <link:label id="lab_fsk_ConsumerDurablesApparelSectorMember_label_en-US" xlink:label="lab_fsk_ConsumerDurablesApparelSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consumer Durables &amp; Apparel Sector [Member]</link:label>
    <link:label id="lab_fsk_ConsumerDurablesApparelSectorMember_documentation_en-US" xlink:label="lab_fsk_ConsumerDurablesApparelSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Consumer Durables &amp; Apparel Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ConsumerDurablesApparelSectorMember" xlink:href="fsk-20260331.xsd#fsk_ConsumerDurablesApparelSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ConsumerDurablesApparelSectorMember" xlink:to="lab_fsk_ConsumerDurablesApparelSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentFiscalPeriodFocus_019d1bac-cc86-7c2b-b90f-9fc82083c260_terseLabel_en-US" xlink:label="lab_dei_DocumentFiscalPeriodFocus" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Fiscal Period Focus</link:label>
    <link:label id="lab_dei_DocumentFiscalPeriodFocus_label_en-US" xlink:label="lab_dei_DocumentFiscalPeriodFocus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Fiscal Period Focus</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentFiscalPeriodFocus" xlink:to="lab_dei_DocumentFiscalPeriodFocus" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EquityDistributionAgreementsMember_019d1bac-ccf8-7093-8c8e-3f2db84251a7_terseLabel_en-US" xlink:label="lab_fsk_EquityDistributionAgreementsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Distribution Agreements</link:label>
    <link:label id="lab_fsk_EquityDistributionAgreementsMember_label_en-US" xlink:label="lab_fsk_EquityDistributionAgreementsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Distribution Agreements [Member]</link:label>
    <link:label id="lab_fsk_EquityDistributionAgreementsMember_documentation_en-US" xlink:label="lab_fsk_EquityDistributionAgreementsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Equity Distribution Agreements</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EquityDistributionAgreementsMember" xlink:href="fsk-20260331.xsd#fsk_EquityDistributionAgreementsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EquityDistributionAgreementsMember" xlink:to="lab_fsk_EquityDistributionAgreementsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_UnsecuredDebtMember_019d1bac-cc86-7bdf-a767-e135954dbaa4_terseLabel_en-US" xlink:label="lab_us-gaap_UnsecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unsecured Notes</link:label>
    <link:label id="lab_us-gaap_UnsecuredDebtMember_label_en-US" xlink:label="lab_us-gaap_UnsecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unsecured Debt [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_UnsecuredDebtMember" xlink:to="lab_us-gaap_UnsecuredDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgMethodTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AwardTmgMethodTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Timing Method</link:label>
    <link:label id="lab_ecd_AwardTmgMethodTextBlock_label_en-US" xlink:label="lab_ecd_AwardTmgMethodTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing Method [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgMethodTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgMethodTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgMethodTextBlock" xlink:to="lab_ecd_AwardTmgMethodTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AwardTypeAxis_terseLabel_en-US" xlink:label="lab_us-gaap_AwardTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Type</link:label>
    <link:label id="lab_us-gaap_AwardTypeAxis_label_en-US" xlink:label="lab_us-gaap_AwardTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AwardTypeAxis" xlink:to="lab_us-gaap_AwardTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnfundedDebtCommitmentsMember_019d1bac-ccf8-7963-8dc7-4af67faf9702_terseLabel_en-US" xlink:label="lab_fsk_UnfundedDebtCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded Debt Commitments</link:label>
    <link:label id="lab_fsk_UnfundedDebtCommitmentsMember_label_en-US" xlink:label="lab_fsk_UnfundedDebtCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unfunded Debt Commitments [Member]</link:label>
    <link:label id="lab_fsk_UnfundedDebtCommitmentsMember_documentation_en-US" xlink:label="lab_fsk_UnfundedDebtCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unfunded Debt Commitments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnfundedDebtCommitmentsMember" xlink:href="fsk-20260331.xsd#fsk_UnfundedDebtCommitmentsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnfundedDebtCommitmentsMember" xlink:to="lab_fsk_UnfundedDebtCommitmentsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongTermDebt_019d1bac-cc86-7553-8538-50ae14a7dcd3_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt (net of deferred financing costs and discount of $42 and $45, respectively)</link:label>
    <link:label id="lab_us-gaap_LongTermDebt_label_en-US" xlink:label="lab_us-gaap_LongTermDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebt" xlink:to="lab_us-gaap_LongTermDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_LegalEntityAxis_019d1bac-cc86-7ed9-9678-e36c99b22000_terseLabel_en-US" xlink:label="lab_dei_LegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Legal Entity [Axis]</link:label>
    <link:label id="lab_dei_LegalEntityAxis_label_en-US" xlink:label="lab_dei_LegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_LegalEntityAxis" xlink:to="lab_dei_LegalEntityAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.80ClassBNotesOutstandingMember_019d9f65-9670-705c-bd5e-04921526ade7_terseLabel_en-US" xlink:label="lab_fsk_A1.80ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.80% Class B Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.80ClassBNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.80ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.80% Class B Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.80ClassBNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.80ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.80% Class B Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.80ClassBNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.80ClassBNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.80ClassBNotesOutstandingMember" xlink:to="lab_fsk_A1.80ClassBNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_Assets_019d1bac-cc86-7a67-b986-7be9bbe20304_totalLabel_en-US" xlink:label="lab_us-gaap_Assets" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total assets</link:label>
    <link:label id="lab_us-gaap_Assets_label_en-US" xlink:label="lab_us-gaap_Assets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_Assets" xlink:to="lab_us-gaap_Assets" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_TradingSymbol_019d1bac-cbe9-7cbe-92b3-48f0a648f695_terseLabel_en-US" xlink:label="lab_dei_TradingSymbol" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Trading Symbol</link:label>
    <link:label id="lab_dei_TradingSymbol_label_en-US" xlink:label="lab_dei_TradingSymbol" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Symbol</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_TradingSymbol" xlink:to="lab_dei_TradingSymbol" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent_019e14be-3cd7-7359-acb6-58fa30c0415b_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Incentive fee waived</link:label>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent_label_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Incentive Fee Waived, Percent</link:label>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Incentive Fee Waived, Percent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyIncentiveFeeWaivedPercent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:to="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercent" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CreditOpportunitiesPartnersJVLLCMember_019d1bac-cc86-783e-9f62-4a7afa4c8679_terseLabel_en-US" xlink:label="lab_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Credit Opportunities Partners JV, LLC</link:label>
    <link:label id="lab_fsk_CreditOpportunitiesPartnersJVLLCMember_019d68a8-d37a-7c04-8a4b-17ea2a0c5d87_verboseLabel_en-US" xlink:label="lab_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Credit Opportunities Partners JV, LLC</link:label>
    <link:label id="lab_fsk_CreditOpportunitiesPartnersJVLLCMember_label_en-US" xlink:label="lab_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Opportunities Partners JV, LLC [Member]</link:label>
    <link:label id="lab_fsk_CreditOpportunitiesPartnersJVLLCMember_documentation_en-US" xlink:label="lab_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Credit Opportunities Partners JV, LLC</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:href="fsk-20260331.xsd#fsk_CreditOpportunitiesPartnersJVLLCMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:to="lab_fsk_CreditOpportunitiesPartnersJVLLCMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember_019d1bac-cbe9-7ccf-bcbe-8345a923db45_terseLabel_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Less Than</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember_label_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Less Than [Member]</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember_documentation_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Term Benchmark, Less Than</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:href="fsk-20260331.xsd#fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:to="lab_fsk_LenderOtherThanNonExtendingLendersTermBenchmarkLessThanMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember_019d1bac-ccf8-728e-952e-1f02a43e56b1_terseLabel_en-US" xlink:label="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Securities, Revolving Credit Facility</link:label>
    <link:label id="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember_label_en-US" xlink:label="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Securities, Revolving Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Securities, Revolving Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_DebtSecuritiesRevolvingCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:to="lab_fsk_DebtSecuritiesRevolvingCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityAddressCityOrTown_019d1bac-cc86-7034-9378-5bbfa552ab2c_terseLabel_en-US" xlink:label="lab_dei_EntityAddressCityOrTown" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Address, City or Town</link:label>
    <link:label id="lab_dei_EntityAddressCityOrTown_label_en-US" xlink:label="lab_dei_EntityAddressCityOrTown" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Address, City or Town</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressCityOrTown" xlink:to="lab_dei_EntityAddressCityOrTown" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle_019d1bac-cbe9-7671-8b78-95fe845f218c_terseLabel_en-US" xlink:label="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Commitment to investment vehicle</link:label>
    <link:label id="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle_label_en-US" xlink:label="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party, Commitment to Investment Vehicle</link:label>
    <link:label id="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle_documentation_en-US" xlink:label="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Related Party, Commitment to Investment Vehicle</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:href="fsk-20260331.xsd#fsk_RelatedPartyCommitmentToInvestmentVehicle"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:to="lab_fsk_RelatedPartyCommitmentToInvestmentVehicle" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019d1bac-cc86-70de-af34-809f427f454c_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash flows from operating activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019df361-c16f-708d-9c4f-ec66cc7ea6c2_terseLabel_en-US" xlink:label="lab_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Effect of exchange rate changes on cash</link:label>
    <link:label id="lab_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_label_en-US" xlink:label="lab_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="lab_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ReceivableInvestmentSale_019d1bac-cbe9-72aa-a767-68d9c3b1e406_terseLabel_en-US" xlink:label="lab_us-gaap_ReceivableInvestmentSale" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Receivable for investments sold and repaid</link:label>
    <link:label id="lab_us-gaap_ReceivableInvestmentSale_label_en-US" xlink:label="lab_us-gaap_ReceivableInvestmentSale" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Receivable, Investment, Sale</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableInvestmentSale" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReceivableInvestmentSale"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ReceivableInvestmentSale" xlink:to="lab_us-gaap_ReceivableInvestmentSale" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ConcentrationRiskByTypeAxis_019d1bac-cc86-7a3e-b786-77dc275ee336_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskByTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Axis]</link:label>
    <link:label id="lab_us-gaap_ConcentrationRiskByTypeAxis_label_en-US" xlink:label="lab_us-gaap_ConcentrationRiskByTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis" xlink:to="lab_us-gaap_ConcentrationRiskByTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonPeoNeoAvgCompActuallyPaidAmt_terseLabel_en-US" xlink:label="lab_ecd_NonPeoNeoAvgCompActuallyPaidAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-PEO NEO Average Compensation Actually Paid Amount</link:label>
    <link:label id="lab_ecd_NonPeoNeoAvgCompActuallyPaidAmt_label_en-US" xlink:label="lab_ecd_NonPeoNeoAvgCompActuallyPaidAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-PEO NEO Average Compensation Actually Paid Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonPeoNeoAvgCompActuallyPaidAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonPeoNeoAvgCompActuallyPaidAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonPeoNeoAvgCompActuallyPaidAmt" xlink:to="lab_ecd_NonPeoNeoAvgCompActuallyPaidAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncomeStatementLocationDomain_019d1bac-cc86-715d-ae61-e3be5a7623a7_terseLabel_en-US" xlink:label="lab_us-gaap_IncomeStatementLocationDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income Statement Location [Domain]</link:label>
    <link:label id="lab_us-gaap_IncomeStatementLocationDomain_label_en-US" xlink:label="lab_us-gaap_IncomeStatementLocationDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Income Location, Balance [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncomeStatementLocationDomain" xlink:to="lab_us-gaap_IncomeStatementLocationDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CompActuallyPaidVsOtherMeasureTextBlock_terseLabel_en-US" xlink:label="lab_ecd_CompActuallyPaidVsOtherMeasureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Other Measure</link:label>
    <link:label id="lab_ecd_CompActuallyPaidVsOtherMeasureTextBlock_label_en-US" xlink:label="lab_ecd_CompActuallyPaidVsOtherMeasureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Other Measure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CompActuallyPaidVsOtherMeasureTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CompActuallyPaidVsOtherMeasureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CompActuallyPaidVsOtherMeasureTextBlock" xlink:to="lab_ecd_CompActuallyPaidVsOtherMeasureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_NumberOfInvestmentsInPortfolioCompanies_019d1bac-cc86-796b-8ee7-f4d7e1f3b88b_terseLabel_en-US" xlink:label="lab_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of investments in portfolio companies</link:label>
    <link:label id="lab_fsk_NumberOfInvestmentsInPortfolioCompanies_label_en-US" xlink:label="lab_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number Of Investments In Portfolio Companies</link:label>
    <link:label id="lab_fsk_NumberOfInvestmentsInPortfolioCompanies_documentation_en-US" xlink:label="lab_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Number Of Investments In Portfolio Companies</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:href="fsk-20260331.xsd#fsk_NumberOfInvestmentsInPortfolioCompanies"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:to="lab_fsk_NumberOfInvestmentsInPortfolioCompanies" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityEmergingGrowthCompany_019d1bac-cc86-78c3-b0f5-0512b0853a19_terseLabel_en-US" xlink:label="lab_dei_EntityEmergingGrowthCompany" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Emerging Growth Company</link:label>
    <link:label id="lab_dei_EntityEmergingGrowthCompany_label_en-US" xlink:label="lab_dei_EntityEmergingGrowthCompany" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Emerging Growth Company</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityEmergingGrowthCompany" xlink:to="lab_dei_EntityEmergingGrowthCompany" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_TechnologyHardwareEquipmentSectorMember_019d1bac-cc86-7cdf-85f3-30279e2390c5_terseLabel_en-US" xlink:label="lab_fsk_TechnologyHardwareEquipmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Technology Hardware &amp; Equipment</link:label>
    <link:label id="lab_fsk_TechnologyHardwareEquipmentSectorMember_label_en-US" xlink:label="lab_fsk_TechnologyHardwareEquipmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Technology Hardware &amp; Equipment Sector [Member]</link:label>
    <link:label id="lab_fsk_TechnologyHardwareEquipmentSectorMember_documentation_en-US" xlink:label="lab_fsk_TechnologyHardwareEquipmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Technology Hardware &amp; Equipment Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_TechnologyHardwareEquipmentSectorMember" xlink:href="fsk-20260331.xsd#fsk_TechnologyHardwareEquipmentSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_TechnologyHardwareEquipmentSectorMember" xlink:to="lab_fsk_TechnologyHardwareEquipmentSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockDividendsPerShareDeclared_019d1bac-cc86-777e-928f-44df4ef31f2f_totalLabel_en-US" xlink:label="lab_us-gaap_CommonStockDividendsPerShareDeclared" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total Dividends Declared (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_CommonStockDividendsPerShareDeclared_019d1bac-cc86-75fb-8ea0-061dc4a29ab2_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockDividendsPerShareDeclared" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Distributions declared per share (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_CommonStockDividendsPerShareDeclared_label_en-US" xlink:label="lab_us-gaap_CommonStockDividendsPerShareDeclared" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Dividends, Per Share, Declared</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockDividendsPerShareDeclared" xlink:to="lab_us-gaap_CommonStockDividendsPerShareDeclared" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityCommonStockSharesOutstanding_019d1bac-cc86-7c30-bc1e-aff58d357055_terseLabel_en-US" xlink:label="lab_dei_EntityCommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Common Stock, Shares Outstanding</link:label>
    <link:label id="lab_dei_EntityCommonStockSharesOutstanding_label_en-US" xlink:label="lab_dei_EntityCommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Common Stock, Shares Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityCommonStockSharesOutstanding" xlink:to="lab_dei_EntityCommonStockSharesOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentOwnedBalancePrincipalAmount_019d1bac-ccf8-7843-a50d-ef5a7403c5d5_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedBalancePrincipalAmount" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Principal Amount</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedBalancePrincipalAmount_label_en-US" xlink:label="lab_us-gaap_InvestmentOwnedBalancePrincipalAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, Balance, Principal Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedBalancePrincipalAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedBalancePrincipalAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentOwnedBalancePrincipalAmount" xlink:to="lab_us-gaap_InvestmentOwnedBalancePrincipalAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeCollateralRightToReclaimCash_019d1bac-cbe9-7486-a169-99e2184d4e3d_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeCollateralRightToReclaimCash" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash Collateral Pledged</link:label>
    <link:label id="lab_us-gaap_DerivativeCollateralRightToReclaimCash_label_en-US" xlink:label="lab_us-gaap_DerivativeCollateralRightToReclaimCash" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralRightToReclaimCash" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeCollateralRightToReclaimCash"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeCollateralRightToReclaimCash" xlink:to="lab_us-gaap_DerivativeCollateralRightToReclaimCash" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SaleOfStockAmountAuthorizedToSell_019d1bac-cc86-792e-8406-53a1bbe999ea_terseLabel_en-US" xlink:label="lab_fsk_SaleOfStockAmountAuthorizedToSell" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amount of stock authorized to sell</link:label>
    <link:label id="lab_fsk_SaleOfStockAmountAuthorizedToSell_label_en-US" xlink:label="lab_fsk_SaleOfStockAmountAuthorizedToSell" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Amount Authorized To Sell</link:label>
    <link:label id="lab_fsk_SaleOfStockAmountAuthorizedToSell_documentation_en-US" xlink:label="lab_fsk_SaleOfStockAmountAuthorizedToSell" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Amount Authorized To Sell</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SaleOfStockAmountAuthorizedToSell" xlink:href="fsk-20260331.xsd#fsk_SaleOfStockAmountAuthorizedToSell"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SaleOfStockAmountAuthorizedToSell" xlink:to="lab_fsk_SaleOfStockAmountAuthorizedToSell" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember_terseLabel_en-US" xlink:label="lab_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year</link:label>
    <link:label id="lab_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember_label_en-US" xlink:label="lab_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember" xlink:to="lab_ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems_019d1bac-cbe9-7897-ba24-5dd5bcb4c565_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Line Items]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems" xlink:to="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueInputsLevel2Member_019d1bac-cc86-7fab-9b3d-3a847a08f994_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel2Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Level 2&#8212;Significant other observable inputs</link:label>
    <link:label id="lab_us-gaap_FairValueInputsLevel2Member_label_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel2Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Inputs, Level 2 [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueInputsLevel2Member" xlink:to="lab_us-gaap_FairValueInputsLevel2Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DeferredFinanceCostsNet_019d1bac-cc86-7574-977a-a8900d014e06_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredFinanceCostsNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt financing costs</link:label>
    <link:label id="lab_us-gaap_DeferredFinanceCostsNet_label_en-US" xlink:label="lab_us-gaap_DeferredFinanceCostsNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Issuance Costs, Net</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DeferredFinanceCostsNet" xlink:to="lab_us-gaap_DeferredFinanceCostsNet" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeGainLossOnDerivativeNet_019d1bac-cc86-7a7e-95d9-dbc685216902_totalLabel_en-US" xlink:label="lab_us-gaap_DerivativeGainLossOnDerivativeNet" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total</link:label>
    <link:label id="lab_us-gaap_DerivativeGainLossOnDerivativeNet_label_en-US" xlink:label="lab_us-gaap_DerivativeGainLossOnDerivativeNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative, Gain (Loss) on Derivative, Net</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNet" xlink:to="lab_us-gaap_DerivativeGainLossOnDerivativeNet" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice_019d1bac-cbe9-7ef3-a221-cc35ce45eeb1_terseLabel_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percent of market price</link:label>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice_label_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Dividend Reinvestment Plan, Percent Of Market Price</link:label>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice_documentation_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Dividend Reinvestment Plan, Percent Of Market Price</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:href="fsk-20260331.xsd#fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:to="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanPercentOfMarketPrice" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock_terseLabel_en-US" xlink:label="lab_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Insider Trading Policies and Procedures Not Adopted</link:label>
    <link:label id="lab_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock_label_en-US" xlink:label="lab_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Insider Trading Policies and Procedures Not Adopted [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock" xlink:to="lab_ecd_InsiderTrdPoliciesProcNotAdoptedTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments_019d1bac-cc86-7469-9e63-bc3222dc95cc_negatedTerseLabel_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Sales and repayments</link:label>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments_label_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Sales And Repayments</link:label>
    <link:label id="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments_documentation_en-US" xlink:label="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Sales And Repayments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:href="fsk-20260331.xsd#fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:to="lab_fsk_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisSalesAndRepayments" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockSharesOutstanding_019d1bac-cc86-74e4-8932-4d9f555451e3_verboseLabel_en-US" xlink:label="lab_us-gaap_CommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Common stock, shares outstanding (in shares)</link:label>
    <link:label id="lab_us-gaap_CommonStockSharesOutstanding_019d1bac-cc86-74fa-8ce2-679dc2f3878a_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shares outstanding, end of period (in shares)</link:label>
    <link:label id="lab_us-gaap_CommonStockSharesOutstanding_label_en-US" xlink:label="lab_us-gaap_CommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Shares, Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockSharesOutstanding" xlink:to="lab_us-gaap_CommonStockSharesOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain_019d1bac-cc86-7bbd-a489-2254ed25ce4d_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term capital gains proceeds from the sale of assets</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Long-Term Capital Gain</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributionLongTermCapitalGain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain" xlink:to="lab_us-gaap_InvestmentCompanyDistributionLongTermCapitalGain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeoMember_terseLabel_en-US" xlink:label="lab_ecd_PeoMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">PEO</link:label>
    <link:label id="lab_ecd_PeoMember_label_en-US" xlink:label="lab_ecd_PeoMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">PEO [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeoMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeoMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeoMember" xlink:to="lab_ecd_PeoMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019d1bac-cc86-7366-a833-ced5f05c3ea1_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Transfers into Level 3</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3" xlink:to="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019d1bac-cc86-75fd-b796-a64cc87e425e_terseLabel_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized gain (loss) on foreign currency</link:label>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_019d1bac-cc86-7158-bdc5-d76813b0f4f4_verboseLabel_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized gain (loss) on foreign currency</link:label>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_label_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:to="lab_us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember_terseLabel_en-US" xlink:label="lab_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year</link:label>
    <link:label id="lab_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember_label_en-US" xlink:label="lab_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember" xlink:to="lab_ecd_DvddsOrOthrErngsPdOnEqtyAwrdsNtOthrwsRflctdInTtlCompForCvrdYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FSKKRCapitalCorpMember_019d1bac-cbe9-70bc-9750-4e2209d98e1d_terseLabel_en-US" xlink:label="lab_fsk_FSKKRCapitalCorpMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">FS KKR Capital Corp.</link:label>
    <link:label id="lab_fsk_FSKKRCapitalCorpMember_label_en-US" xlink:label="lab_fsk_FSKKRCapitalCorpMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">FS KKR Capital Corp. [Member]</link:label>
    <link:label id="lab_fsk_FSKKRCapitalCorpMember_documentation_en-US" xlink:label="lab_fsk_FSKKRCapitalCorpMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">FS KKR Capital Corp.</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FSKKRCapitalCorpMember" xlink:href="fsk-20260331.xsd#fsk_FSKKRCapitalCorpMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FSKKRCapitalCorpMember" xlink:to="lab_fsk_FSKKRCapitalCorpMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_label_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instruments and Hedging Activities Disclosure [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentInterestRateFloor_019d1bac-cc86-7c89-b9d5-eb82e91221af_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentInterestRateFloor" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Floor</link:label>
    <link:label id="lab_us-gaap_InvestmentInterestRateFloor_label_en-US" xlink:label="lab_us-gaap_InvestmentInterestRateFloor" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Interest Rate, Floor</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentInterestRateFloor" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentInterestRateFloor"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentInterestRateFloor" xlink:to="lab_us-gaap_InvestmentInterestRateFloor" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A3250UnsecuredNotesDue2027Member_019d1bac-cc86-7ad3-a3dc-58dbf8f5b067_terseLabel_en-US" xlink:label="lab_fsk_A3250UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">3.250% Notes due 2027</link:label>
    <link:label id="lab_fsk_A3250UnsecuredNotesDue2027Member_label_en-US" xlink:label="lab_fsk_A3250UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">3.250% Unsecured Notes due 2027 [Member]</link:label>
    <link:label id="lab_fsk_A3250UnsecuredNotesDue2027Member_documentation_en-US" xlink:label="lab_fsk_A3250UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">3.250% Unsecured Notes due 2027</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A3250UnsecuredNotesDue2027Member" xlink:href="fsk-20260331.xsd#fsk_A3250UnsecuredNotesDue2027Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A3250UnsecuredNotesDue2027Member" xlink:to="lab_fsk_A3250UnsecuredNotesDue2027Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyPerShareDataAbstract_019d1bac-cc86-7731-97f8-e220b78c47bf_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyPerShareDataAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Per Share Data</link:label>
    <link:label id="lab_fsk_InvestmentCompanyPerShareDataAbstract_label_en-US" xlink:label="lab_fsk_InvestmentCompanyPerShareDataAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Per Share Data [Abstract]</link:label>
    <link:label id="lab_fsk_InvestmentCompanyPerShareDataAbstract_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyPerShareDataAbstract" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Per Share Data</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyPerShareDataAbstract" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyPerShareDataAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyPerShareDataAbstract" xlink:to="lab_fsk_InvestmentCompanyPerShareDataAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019d1bac-cbe9-78d9-b646-36184372a15b_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Effective interest rate percentage (as percent)</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Interest Rate, Effective Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:to="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityAddressPostalZipCode_019d1bac-cbe9-70ae-8a7d-a76b6d360f24_terseLabel_en-US" xlink:label="lab_dei_EntityAddressPostalZipCode" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Address, Postal Zip Code</link:label>
    <link:label id="lab_dei_EntityAddressPostalZipCode_label_en-US" xlink:label="lab_dei_EntityAddressPostalZipCode" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Address, Postal Zip Code</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressPostalZipCode" xlink:to="lab_dei_EntityAddressPostalZipCode" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_RestatementDeterminationDate_terseLabel_en-US" xlink:label="lab_ecd_RestatementDeterminationDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restatement Determination Date</link:label>
    <link:label id="lab_ecd_RestatementDeterminationDate_label_en-US" xlink:label="lab_ecd_RestatementDeterminationDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restatement Determination Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_RestatementDeterminationDate" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_RestatementDeterminationDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_RestatementDeterminationDate" xlink:to="lab_ecd_RestatementDeterminationDate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019d1bac-cc86-7c1b-b7d0-f5eca4890ed7_periodStartLabel_en-US" xlink:label="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Cash, cash equivalents, restricted cash and foreign currency at beginning of period</link:label>
    <link:label id="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019d1bac-cc86-7795-be9b-7b8f7bfeb99a_periodEndLabel_en-US" xlink:label="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Cash, cash equivalents, restricted cash and foreign currency at end of period</link:label>
    <link:label id="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_label_en-US" xlink:label="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncomeStatementAbstract_label_en-US" xlink:label="lab_us-gaap_IncomeStatementAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Statement [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncomeStatementAbstract" xlink:to="lab_us-gaap_IncomeStatementAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019d1bac-ccf8-7228-b3f2-8f7ef5ce14f4_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Basis spread on variable rate (as percent)</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Basis Spread on Variable Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:to="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockholdersEquityPeriodIncreaseDecrease_019d1bac-cbe9-7458-9c5e-6b19306b45e4_totalLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityPeriodIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total increase (decrease) in net assets</link:label>
    <link:label id="lab_us-gaap_StockholdersEquityPeriodIncreaseDecrease_label_en-US" xlink:label="lab_us-gaap_StockholdersEquityPeriodIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stockholders' Equity, Period Increase (Decrease)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityPeriodIncreaseDecrease"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockholdersEquityPeriodIncreaseDecrease" xlink:to="lab_us-gaap_StockholdersEquityPeriodIncreaseDecrease" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019d1bac-cc86-77c2-b7e3-72a1c0e5ef14_periodStartLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Fair value at beginning of period</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019d1bac-cbe9-7406-af29-63774ee7815f_periodEndLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Fair value at end of period</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:to="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInInterestPayableNet_019d1bac-cc86-746d-89e5-8d9fa7fa41cb_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in interest payable</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInInterestPayableNet_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Interest Payable, Net</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:to="lab_us-gaap_IncreaseDecreaseInInterestPayableNet" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_019d1bac-cc86-7565-b7bf-ff92ae6b1c7a_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Purchases of investments</link:label>
    <link:label id="lab_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity_label_en-US" xlink:label="lab_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payment for Purchase, Investment, Operating Activity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity" xlink:to="lab_us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockSharesIssued_019d1bac-cc86-7ae1-a28d-e4ae0c7caf09_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockSharesIssued" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, shares issued (in shares)</link:label>
    <link:label id="lab_us-gaap_PreferredStockSharesIssued_label_en-US" xlink:label="lab_us-gaap_PreferredStockSharesIssued" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Shares Issued</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockSharesIssued" xlink:to="lab_us-gaap_PreferredStockSharesIssued" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PnsnAdjsSvcCstMember_terseLabel_en-US" xlink:label="lab_ecd_PnsnAdjsSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pension Adjustments Service Cost</link:label>
    <link:label id="lab_ecd_PnsnAdjsSvcCstMember_label_en-US" xlink:label="lab_ecd_PnsnAdjsSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pension Adjustments Service Cost [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PnsnAdjsSvcCstMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PnsnAdjsSvcCstMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PnsnAdjsSvcCstMember" xlink:to="lab_ecd_PnsnAdjsSvcCstMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RealEstateSectorMember_019d1bac-cc86-74ce-abbb-f954fd0d1e6a_terseLabel_en-US" xlink:label="lab_us-gaap_RealEstateSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Real Estate Management &amp; Development</link:label>
    <link:label id="lab_us-gaap_RealEstateSectorMember_label_en-US" xlink:label="lab_us-gaap_RealEstateSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Real Estate Sector [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateSectorMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RealEstateSectorMember" xlink:to="lab_us-gaap_RealEstateSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ProductsAndServicesDomain_019d1bac-cc86-710e-9ea3-747782cbdba2_terseLabel_en-US" xlink:label="lab_srt_ProductsAndServicesDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Product and Service [Domain]</link:label>
    <link:label id="lab_srt_ProductsAndServicesDomain_label_en-US" xlink:label="lab_srt_ProductsAndServicesDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product and Service [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ProductsAndServicesDomain" xlink:to="lab_srt_ProductsAndServicesDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueByFairValueHierarchyLevelAxis_019d1bac-cc86-7160-a6e3-d0b8a420c8d9_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Axis]</link:label>
    <link:label id="lab_us-gaap_FairValueByFairValueHierarchyLevelAxis_label_en-US" xlink:label="lab_us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="lab_us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CustomerConcentrationRiskMember_019d1bac-cc86-7be4-8ebe-e6dc47e70fce_terseLabel_en-US" xlink:label="lab_us-gaap_CustomerConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Customer Concentration Risk</link:label>
    <link:label id="lab_us-gaap_CustomerConcentrationRiskMember_label_en-US" xlink:label="lab_us-gaap_CustomerConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Customer Concentration Risk [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CustomerConcentrationRiskMember" xlink:to="lab_us-gaap_CustomerConcentrationRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyTotalReturn_019d1bac-ccf8-7f4e-86bd-155959c83633_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTotalReturn" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total return based on net asset value</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyTotalReturn_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTotalReturn" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Total Return</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTotalReturn" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTotalReturn"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyTotalReturn" xlink:to="lab_us-gaap_InvestmentCompanyTotalReturn" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestExpenseDebtExcludingAmortization_019d1bac-cc86-722d-b42c-5c9b99e36539_terseLabel_en-US" xlink:label="lab_us-gaap_InterestExpenseDebtExcludingAmortization" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Direct Interest Expense</link:label>
    <link:label id="lab_us-gaap_InterestExpenseDebtExcludingAmortization_label_en-US" xlink:label="lab_us-gaap_InterestExpenseDebtExcludingAmortization" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Expense, Debt, Excluding Amortization</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestExpenseDebtExcludingAmortization" xlink:to="lab_us-gaap_InterestExpenseDebtExcludingAmortization" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract_019d1bac-ccf8-7cf7-beef-3898dfd3910e_terseLabel_en-US" xlink:label="lab_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Realized and unrealized gain/loss</link:label>
    <link:label id="lab_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract_label_en-US" xlink:label="lab_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Realized Gain (Loss), Investment and Derivative, Operating, before Tax [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract" xlink:to="lab_us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingBeforeTaxAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetInvestmentIncome_019d1bac-ccf8-73e6-9512-5d8bea2031c5_terseLabel_en-US" xlink:label="lab_us-gaap_NetInvestmentIncome" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net investment income</link:label>
    <link:label id="lab_us-gaap_NetInvestmentIncome_label_en-US" xlink:label="lab_us-gaap_NetInvestmentIncome" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Investment Income</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentIncome"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetInvestmentIncome" xlink:to="lab_us-gaap_NetInvestmentIncome" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation_019d1bac-cc86-7287-87f0-ac8e06947f45_terseLabel_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized depreciation</link:label>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation_label_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Tax Basis, Unrealized Loss</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation" xlink:to="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.48ClassA1NotesOutstandingMember_019d1bac-cbe9-7ff9-9079-7c6b5de58672_terseLabel_en-US" xlink:label="lab_fsk_A1.48ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.48% Class A-1 Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.48ClassA1NotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.48ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.48% Class A-1 Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.48ClassA1NotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.48ClassA1NotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.48% Class A-1 Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.48ClassA1NotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.48ClassA1NotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.48ClassA1NotesOutstandingMember" xlink:to="lab_fsk_A1.48ClassA1NotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ProfitLoss_019d1bac-cc86-7ad5-a2b8-342b4599de46_totalLabel_en-US" xlink:label="lab_us-gaap_ProfitLoss" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net increase in net assets resulting from operations</link:label>
    <link:label id="lab_us-gaap_ProfitLoss_label_en-US" xlink:label="lab_us-gaap_ProfitLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProfitLoss" xlink:to="lab_us-gaap_ProfitLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_TelecommunicationServicesSectorMember_019d1bac-cc86-7ba7-b9fc-54d92f731b5f_terseLabel_en-US" xlink:label="lab_fsk_TelecommunicationServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Telecommunication Services</link:label>
    <link:label id="lab_fsk_TelecommunicationServicesSectorMember_label_en-US" xlink:label="lab_fsk_TelecommunicationServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Telecommunication Services Sector [Member]</link:label>
    <link:label id="lab_fsk_TelecommunicationServicesSectorMember_documentation_en-US" xlink:label="lab_fsk_TelecommunicationServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Telecommunication Services Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_TelecommunicationServicesSectorMember" xlink:href="fsk-20260331.xsd#fsk_TelecommunicationServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_TelecommunicationServicesSectorMember" xlink:to="lab_fsk_TelecommunicationServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_RestatementDoesNotRequireRecoveryTextBlock_terseLabel_en-US" xlink:label="lab_ecd_RestatementDoesNotRequireRecoveryTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restatement does not require Recovery</link:label>
    <link:label id="lab_ecd_RestatementDoesNotRequireRecoveryTextBlock_label_en-US" xlink:label="lab_ecd_RestatementDoesNotRequireRecoveryTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restatement Does Not Require Recovery [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_RestatementDoesNotRequireRecoveryTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_RestatementDoesNotRequireRecoveryTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_RestatementDoesNotRequireRecoveryTextBlock" xlink:to="lab_ecd_RestatementDoesNotRequireRecoveryTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_label_en-US" xlink:label="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:to="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeNotionalAmount_019d1bac-cc86-7792-88bb-6d27bdb16f2b_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeNotionalAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Current Value</link:label>
    <link:label id="lab_us-gaap_DerivativeNotionalAmount_019d1bac-cc86-7a39-99c6-264767bcbee4_verboseLabel_en-US" xlink:label="lab_us-gaap_DerivativeNotionalAmount" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Derivative, notional amount</link:label>
    <link:label id="lab_us-gaap_DerivativeNotionalAmount_019d1bac-cc86-775a-a4a5-5f1dc2d52575_netLabel_en-US" xlink:label="lab_us-gaap_DerivativeNotionalAmount" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Notional Amount</link:label>
    <link:label id="lab_us-gaap_DerivativeNotionalAmount_label_en-US" xlink:label="lab_us-gaap_DerivativeNotionalAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative, Notional Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeNotionalAmount" xlink:to="lab_us-gaap_DerivativeNotionalAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDividendDistribution_019d1bac-ccf8-7e76-a7d5-72c7cf3bfad1_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDividendDistribution" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Distributions to stockholders</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDividendDistribution_019d1bac-ccf8-7d79-9071-5ffa01fba5e2_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDividendDistribution" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDividendDistribution_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDividendDistribution" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Dividend Distribution</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDividendDistribution" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDividendDistribution"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDividendDistribution" xlink:to="lab_us-gaap_InvestmentCompanyDividendDistribution" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock_terseLabel_en-US" xlink:label="lab_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Company Selected Measure</link:label>
    <link:label id="lab_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock_label_en-US" xlink:label="lab_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Company Selected Measure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock" xlink:to="lab_ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_CityAreaCode_019d1bac-ccf8-79f3-baf0-40de6e9ffbc3_terseLabel_en-US" xlink:label="lab_dei_CityAreaCode" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">City Area Code</link:label>
    <link:label id="lab_dei_CityAreaCode_label_en-US" xlink:label="lab_dei_CityAreaCode" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">City Area Code</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_CityAreaCode" xlink:to="lab_dei_CityAreaCode" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgHowMnpiCnsdrdTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AwardTmgHowMnpiCnsdrdTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award Timing, How MNPI Considered</link:label>
    <link:label id="lab_ecd_AwardTmgHowMnpiCnsdrdTextBlock_label_en-US" xlink:label="lab_ecd_AwardTmgHowMnpiCnsdrdTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing, How MNPI Considered [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgHowMnpiCnsdrdTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgHowMnpiCnsdrdTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgHowMnpiCnsdrdTextBlock" xlink:to="lab_ecd_AwardTmgHowMnpiCnsdrdTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentTextBlock_019d1bac-cbe9-7ccf-8f62-b7badf82c5aa_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Portfolio</link:label>
    <link:label id="lab_us-gaap_InvestmentTextBlock_label_en-US" xlink:label="lab_us-gaap_InvestmentTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentTextBlock" xlink:to="lab_us-gaap_InvestmentTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AllTradingArrangementsMember_terseLabel_en-US" xlink:label="lab_ecd_AllTradingArrangementsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Trading Arrangements</link:label>
    <link:label id="lab_ecd_AllTradingArrangementsMember_label_en-US" xlink:label="lab_ecd_AllTradingArrangementsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Trading Arrangements [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllTradingArrangementsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllTradingArrangementsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="lab_ecd_AllTradingArrangementsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_EqtyAwrdsAdjFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments, Footnote</link:label>
    <link:label id="lab_ecd_EqtyAwrdsAdjFnTextBlock_label_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_EqtyAwrdsAdjFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_EqtyAwrdsAdjFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_EqtyAwrdsAdjFnTextBlock" xlink:to="lab_ecd_EqtyAwrdsAdjFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TotalShareholderRtnVsPeerGroupTextBlock_terseLabel_en-US" xlink:label="lab_ecd_TotalShareholderRtnVsPeerGroupTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total Shareholder Return Vs Peer Group</link:label>
    <link:label id="lab_ecd_TotalShareholderRtnVsPeerGroupTextBlock_label_en-US" xlink:label="lab_ecd_TotalShareholderRtnVsPeerGroupTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Total Shareholder Return Vs Peer Group [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TotalShareholderRtnVsPeerGroupTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TotalShareholderRtnVsPeerGroupTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TotalShareholderRtnVsPeerGroupTextBlock" xlink:to="lab_ecd_TotalShareholderRtnVsPeerGroupTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_currency_USD_019d1bac-cc86-706d-aa29-ea0fec1ccf5e_terseLabel_en-US" xlink:label="lab_currency_USD" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">United States of America, Dollars</link:label>
    <link:label id="lab_currency_USD_label_en-US" xlink:label="lab_currency_USD" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">United States of America, Dollars</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_currency_USD" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_USD"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_currency_USD" xlink:to="lab_currency_USD" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommitmentsAndContingenciesDisclosureAbstract_label_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies Disclosure [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="lab_us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_019d1bac-ccf8-77ff-b57b-37d319391852_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total expenses</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement" xlink:to="lab_us-gaap_InvestmentCompanyExpenseAfterReductionOfFeeWaiverAndReimbursement" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PvpTable_terseLabel_en-US" xlink:label="lab_ecd_PvpTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pay vs Performance Disclosure</link:label>
    <link:label id="lab_ecd_PvpTable_label_en-US" xlink:label="lab_ecd_PvpTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pay vs Performance Disclosure [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PvpTable" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PvpTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PvpTable" xlink:to="lab_ecd_PvpTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_O2025M2AggregateDividendsMember_019d660c-237a-73d5-a62f-27b5adf10957_terseLabel_en-US" xlink:label="lab_fsk_O2025M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">O 2025 M2 Aggregate Dividends</link:label>
    <link:label id="lab_fsk_O2025M2AggregateDividendsMember_label_en-US" xlink:label="lab_fsk_O2025M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">O 2025 M2 Aggregate Dividends [Member]</link:label>
    <link:label id="lab_fsk_O2025M2AggregateDividendsMember_documentation_en-US" xlink:label="lab_fsk_O2025M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">O 2025 M2 Aggregate Dividends</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_O2025M2AggregateDividendsMember" xlink:href="fsk-20260331.xsd#fsk_O2025M2AggregateDividendsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_O2025M2AggregateDividendsMember" xlink:to="lab_fsk_O2025M2AggregateDividendsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivities_019d1bac-cc86-7e76-9557-3239f49f4fee_totalLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash provided by (used in) operating activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivities_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="lab_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionsAbstract_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transactions [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionsAbstract" xlink:to="lab_us-gaap_RelatedPartyTransactionsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncentiveFeeExpense_019d1bac-ccf8-7226-9451-057d39bb6e33_terseLabel_en-US" xlink:label="lab_us-gaap_IncentiveFeeExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subordinated income incentive fees</link:label>
    <link:label id="lab_us-gaap_IncentiveFeeExpense_019d1bac-ccf8-7b26-a3cd-251e3f90bffc_verboseLabel_en-US" xlink:label="lab_us-gaap_IncentiveFeeExpense" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Subordinated Incentive Fee on Income</link:label>
    <link:label id="lab_us-gaap_IncentiveFeeExpense_label_en-US" xlink:label="lab_us-gaap_IncentiveFeeExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Incentive Fee Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncentiveFeeExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncentiveFeeExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncentiveFeeExpense" xlink:to="lab_us-gaap_IncentiveFeeExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward_019d1bac-cc86-7a42-8782-88a5ea133280_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments in and Advances to Affiliates, at Fair Value [Roll Forward]</link:label>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward_label_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments in and Advances to Affiliates, at Fair Value [Roll Forward]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward" xlink:to="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueRollForward" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockParOrStatedValuePerShare_019d1bac-cc86-72dc-a2ff-87f157b672ce_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, par value (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_PreferredStockParOrStatedValuePerShare_label_en-US" xlink:label="lab_us-gaap_PreferredStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Par or Stated Value Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="lab_us-gaap_PreferredStockParOrStatedValuePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventMember_019d1bac-cc86-7ab3-b18a-e8e1a928e07c_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Event</link:label>
    <link:label id="lab_us-gaap_SubsequentEventMember_label_en-US" xlink:label="lab_us-gaap_SubsequentEventMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventMember" xlink:to="lab_us-gaap_SubsequentEventMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_RelatedPartyInvestmentVehicle_019d1bac-cc86-7dd7-a2b1-c5869c651418_terseLabel_en-US" xlink:label="lab_fsk_RelatedPartyInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment vehicle</link:label>
    <link:label id="lab_fsk_RelatedPartyInvestmentVehicle_label_en-US" xlink:label="lab_fsk_RelatedPartyInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party, Investment Vehicle</link:label>
    <link:label id="lab_fsk_RelatedPartyInvestmentVehicle_documentation_en-US" xlink:label="lab_fsk_RelatedPartyInvestmentVehicle" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Related Party, Investment Vehicle</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_RelatedPartyInvestmentVehicle" xlink:href="fsk-20260331.xsd#fsk_RelatedPartyInvestmentVehicle"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_RelatedPartyInvestmentVehicle" xlink:to="lab_fsk_RelatedPartyInvestmentVehicle" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherLiabilities_019d1bac-ccf8-7532-bbb4-ae73d4b6c0dd_terseLabel_en-US" xlink:label="lab_us-gaap_OtherLiabilities" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other liabilities</link:label>
    <link:label id="lab_us-gaap_OtherLiabilities_label_en-US" xlink:label="lab_us-gaap_OtherLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherLiabilities" xlink:to="lab_us-gaap_OtherLiabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned_019d1bac-cc86-7826-97e8-1434e4641ac5_terseLabel_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross investment income attributable to cash income earned</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned_label_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable to Cash Income Earned</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned_documentation_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable to Cash Income Earned</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:href="fsk-20260331.xsd#fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:to="lab_fsk_GrossInvestmentIncomePercentageAttributableToCashIncomeEarned" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_EquityValuationAssumptionDifferenceFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_EquityValuationAssumptionDifferenceFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Valuation Assumption Difference, Footnote</link:label>
    <link:label id="lab_ecd_EquityValuationAssumptionDifferenceFnTextBlock_label_en-US" xlink:label="lab_ecd_EquityValuationAssumptionDifferenceFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Valuation Assumption Difference, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_EquityValuationAssumptionDifferenceFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_EquityValuationAssumptionDifferenceFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_EquityValuationAssumptionDifferenceFnTextBlock" xlink:to="lab_ecd_EquityValuationAssumptionDifferenceFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeoTotalCompAmt_terseLabel_en-US" xlink:label="lab_ecd_PeoTotalCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">PEO Total Compensation Amount</link:label>
    <link:label id="lab_ecd_PeoTotalCompAmt_label_en-US" xlink:label="lab_ecd_PeoTotalCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">PEO Total Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeoTotalCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeoTotalCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeoTotalCompAmt" xlink:to="lab_ecd_PeoTotalCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongtermDebtTypeAxis_019d1bac-cc86-7f93-bb79-d1028a5f6988_terseLabel_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Type [Axis]</link:label>
    <link:label id="lab_us-gaap_LongtermDebtTypeAxis_label_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongtermDebtTypeAxis" xlink:to="lab_us-gaap_LongtermDebtTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansSecondLienMember_019d1bac-cc86-7eb6-a39d-5cd7b36fb08a_terseLabel_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Funded, Senior Secured Loans&#8212;Second Lien</link:label>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansSecondLienMember_label_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Funded, Senior&#160;Secured Loans, Second Lien [Member]</link:label>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansSecondLienMember_documentation_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Funded, Senior&#160;Secured Loans, Second Lien</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:href="fsk-20260331.xsd#fsk_FundedSeniorSecuredLoansSecondLienMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:to="lab_fsk_FundedSeniorSecuredLoansSecondLienMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_MoneyMarketFundsMember_019dfefd-4bbd-714d-b7fa-12fbbfbcb126_terseLabel_en-US" xlink:label="lab_us-gaap_MoneyMarketFundsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Money Market Funds</link:label>
    <link:label id="lab_us-gaap_MoneyMarketFundsMember_label_en-US" xlink:label="lab_us-gaap_MoneyMarketFundsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Money Market Funds [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_MoneyMarketFundsMember" xlink:to="lab_us-gaap_MoneyMarketFundsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentInterestRatePaidInKind_019d1bac-cc86-7ebd-a73e-cce3561b3ec9_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentInterestRatePaidInKind" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">PIK Rate (as percent)</link:label>
    <link:label id="lab_us-gaap_InvestmentInterestRatePaidInKind_label_en-US" xlink:label="lab_us-gaap_InvestmentInterestRatePaidInKind" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Interest Rate, Paid in Kind</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentInterestRatePaidInKind" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentInterestRatePaidInKind"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentInterestRatePaidInKind" xlink:to="lab_us-gaap_InvestmentInterestRatePaidInKind" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock_019d1bac-cc86-74e6-8c70-91ad113fc47b_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Cash Distributions Paid on Common Stock Including Tax Basis</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution To Shareholders [Table Text Block]</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution To Shareholders</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:to="lab_fsk_InvestmentCompanyDistributionToShareholdersTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiability_019d1bac-cbe9-78a9-a745-0c64a3811d51_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized depreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiability_019d1bac-cbe9-70d4-8560-41c577d79514_negatedLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Unrealized depreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiability_019d1bac-cbe9-73e7-b86d-d7020ee2d168_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Derivative Liabilities Subject to Master Netting Agreement</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiability_019d1bac-cbe9-767c-9fe7-75fb4efd978d_netLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Gross Amount of Recognized Liabilities</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiability_label_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability, Subject to Master Netting Arrangement, before Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:to="lab_us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfInvestmentsAbstract_label_en-US" xlink:label="lab_us-gaap_ScheduleOfInvestmentsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Investments [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfInvestmentsAbstract" xlink:to="lab_us-gaap_ScheduleOfInvestmentsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnfundedDebtSecuritiesMember_019d1bac-cbe9-7196-a49e-3c2dd27748db_terseLabel_en-US" xlink:label="lab_fsk_UnfundedDebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded Debt Securities</link:label>
    <link:label id="lab_fsk_UnfundedDebtSecuritiesMember_label_en-US" xlink:label="lab_fsk_UnfundedDebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unfunded Debt Securities [Member]</link:label>
    <link:label id="lab_fsk_UnfundedDebtSecuritiesMember_documentation_en-US" xlink:label="lab_fsk_UnfundedDebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unfunded Debt Securities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnfundedDebtSecuritiesMember" xlink:href="fsk-20260331.xsd#fsk_UnfundedDebtSecuritiesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnfundedDebtSecuritiesMember" xlink:to="lab_fsk_UnfundedDebtSecuritiesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CanadianDollarOfferRateMember_019d1bac-ccf8-78e9-81ec-5cbc31e842db_terseLabel_en-US" xlink:label="lab_fsk_CanadianDollarOfferRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">CDOR</link:label>
    <link:label id="lab_fsk_CanadianDollarOfferRateMember_label_en-US" xlink:label="lab_fsk_CanadianDollarOfferRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Canadian Dollar Offer Rate [Member]</link:label>
    <link:label id="lab_fsk_CanadianDollarOfferRateMember_documentation_en-US" xlink:label="lab_fsk_CanadianDollarOfferRateMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Canadian Dollar Offer Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CanadianDollarOfferRateMember" xlink:href="fsk-20260331.xsd#fsk_CanadianDollarOfferRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CanadianDollarOfferRateMember" xlink:to="lab_fsk_CanadianDollarOfferRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_019d1bac-cc86-7f97-9be5-09abc2c588a3_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Transfers out of Level 3</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3" xlink:to="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StandbyLettersOfCreditMember_019d1bac-cc86-7fe3-a684-5381b9bfc8cf_terseLabel_en-US" xlink:label="lab_us-gaap_StandbyLettersOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Standby Letters of Credit</link:label>
    <link:label id="lab_us-gaap_StandbyLettersOfCreditMember_label_en-US" xlink:label="lab_us-gaap_StandbyLettersOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Standby Letters of Credit [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StandbyLettersOfCreditMember" xlink:to="lab_us-gaap_StandbyLettersOfCreditMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonRule10b51ArrAdoptedFlag_terseLabel_en-US" xlink:label="lab_ecd_NonRule10b51ArrAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-Rule 10b5-1 Arrangement Adopted</link:label>
    <link:label id="lab_ecd_NonRule10b51ArrAdoptedFlag_label_en-US" xlink:label="lab_ecd_NonRule10b51ArrAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-Rule 10b5-1 Arrangement Adopted [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonRule10b51ArrAdoptedFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonRule10b51ArrAdoptedFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonRule10b51ArrAdoptedFlag" xlink:to="lab_ecd_NonRule10b51ArrAdoptedFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NumberOfReportableSegments_019d1bac-ccf8-7ce0-aa48-07d6b80d5e7b_terseLabel_en-US" xlink:label="lab_us-gaap_NumberOfReportableSegments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of reportable segments</link:label>
    <link:label id="lab_us-gaap_NumberOfReportableSegments_label_en-US" xlink:label="lab_us-gaap_NumberOfReportableSegments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number of Reportable Segments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NumberOfReportableSegments" xlink:to="lab_us-gaap_NumberOfReportableSegments" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_019d1bac-cbe9-7457-98df-89c252215aaa_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Financial Highlights</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Highlights [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:to="lab_us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SupplementalCashFlowInformationAbstract_019d1bac-cc86-798d-a610-499ab223c283_terseLabel_en-US" xlink:label="lab_us-gaap_SupplementalCashFlowInformationAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Supplemental disclosure</link:label>
    <link:label id="lab_us-gaap_SupplementalCashFlowInformationAbstract_label_en-US" xlink:label="lab_us-gaap_SupplementalCashFlowInformationAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Supplemental Cash Flow Information [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="lab_us-gaap_SupplementalCashFlowInformationAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_OtherPerfMeasureAmt_terseLabel_en-US" xlink:label="lab_ecd_OtherPerfMeasureAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Performance Measure, Amount</link:label>
    <link:label id="lab_ecd_OtherPerfMeasureAmt_label_en-US" xlink:label="lab_ecd_OtherPerfMeasureAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Performance Measure, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_OtherPerfMeasureAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_OtherPerfMeasureAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_OtherPerfMeasureAmt" xlink:to="lab_ecd_OtherPerfMeasureAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsOfDebtIssuanceCosts_019d1bac-cc86-7723-9985-2fca77c2cdb1_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsOfDebtIssuanceCosts" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Deferred financing costs paid</link:label>
    <link:label id="lab_us-gaap_PaymentsOfDebtIssuanceCosts_label_en-US" xlink:label="lab_us-gaap_PaymentsOfDebtIssuanceCosts" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payments of Debt Issuance Costs</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsOfDebtIssuanceCosts" xlink:to="lab_us-gaap_PaymentsOfDebtIssuanceCosts" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityAddressStateOrProvince_019d1bac-cc86-765c-b444-87c9a31636c6_terseLabel_en-US" xlink:label="lab_dei_EntityAddressStateOrProvince" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Address, State or Province</link:label>
    <link:label id="lab_dei_EntityAddressStateOrProvince_label_en-US" xlink:label="lab_dei_EntityAddressStateOrProvince" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Address, State or Province</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressStateOrProvince" xlink:to="lab_dei_EntityAddressStateOrProvince" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_019d1bac-cbe9-7eea-b5f8-f6ad11a5d7a2_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio of net investment income to average net assets</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Investment Income (Loss) Ratio</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossRatio"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:to="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DelayedDrawTermLoanMember_019d1bac-cc86-7650-af1b-b841a48be93b_terseLabel_en-US" xlink:label="lab_us-gaap_DelayedDrawTermLoanMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Delayed Draw Term Loan (DDTL)</link:label>
    <link:label id="lab_us-gaap_DelayedDrawTermLoanMember_label_en-US" xlink:label="lab_us-gaap_DelayedDrawTermLoanMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Delayed Draw Term Loan (DDTL) [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DelayedDrawTermLoanMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DelayedDrawTermLoanMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DelayedDrawTermLoanMember" xlink:to="lab_us-gaap_DelayedDrawTermLoanMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_019d1bac-ccf8-7166-9f00-33f6c7eb431d_terseLabel_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income tax purposes</link:label>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes_label_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Tax Basis, Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes" xlink:to="lab_us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementPolicyPolicyTextBlock_019d1bac-cc86-7665-b1d3-7b3c36a0dd37_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value Measurement</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementPolicyPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Measurement, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementPolicyPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:to="lab_us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_currency_EUR_019daac7-b8e5-7447-8bfb-744a852d97e3_verboseLabel_en-US" xlink:label="lab_currency_EUR" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">EUR</link:label>
    <link:label id="lab_currency_EUR_label_en-US" xlink:label="lab_currency_EUR" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Euro Member Countries, Euro</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_currency_EUR" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_EUR"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_currency_EUR" xlink:to="lab_currency_EUR" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyDomain_019d1bac-cc86-77cc-82fa-a01ec2e0a4e9_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party [Domain]</link:label>
    <link:label id="lab_us-gaap_RelatedPartyDomain_label_en-US" xlink:label="lab_us-gaap_RelatedPartyDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related and Nonrelated Parties [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyDomain" xlink:to="lab_us-gaap_RelatedPartyDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember_019d1bac-ccf8-767b-8f7b-e5caec6f0b6f_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-controlled/affiliated</link:label>
    <link:label id="lab_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember_label_en-US" xlink:label="lab_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Affiliated Issuer, Noncontrolled [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember" xlink:to="lab_us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNetAssetsRollForward_019d1bac-ccf8-7a25-a8ec-2ed0ac0a4fa4_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNetAssetsRollForward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Net Assets [Roll Forward]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNetAssetsRollForward_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNetAssetsRollForward" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Net Assets [Roll Forward]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNetAssetsRollForward" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNetAssetsRollForward"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNetAssetsRollForward" xlink:to="lab_us-gaap_InvestmentCompanyNetAssetsRollForward" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeInstrumentRiskAxis_019d1bac-cc86-79df-aee5-86adf4ea0ac5_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentRiskAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Instrument [Axis]</link:label>
    <link:label id="lab_us-gaap_DerivativeInstrumentRiskAxis_label_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentRiskAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instrument [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis" xlink:to="lab_us-gaap_DerivativeInstrumentRiskAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_IndividualAxis_terseLabel_en-US" xlink:label="lab_ecd_IndividualAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Individual:</link:label>
    <link:label id="lab_ecd_IndividualAxis_label_en-US" xlink:label="lab_ecd_IndividualAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Individual [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_IndividualAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_IndividualAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_IndividualAxis" xlink:to="lab_ecd_IndividualAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RestrictedCash_019df2a7-d813-7edd-bc82-e9e3985f488a_terseLabel_en-US" xlink:label="lab_us-gaap_RestrictedCash" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:label id="lab_us-gaap_RestrictedCash_label_en-US" xlink:label="lab_us-gaap_RestrictedCash" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted Cash</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCash"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RestrictedCash" xlink:to="lab_us-gaap_RestrictedCash" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsOfDividendsCommonStock_019d1bac-cc86-7ee6-89c3-3cba52f83576_negatedLabel_en-US" xlink:label="lab_us-gaap_PaymentsOfDividendsCommonStock" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Stockholder distributions</link:label>
    <link:label id="lab_us-gaap_PaymentsOfDividendsCommonStock_label_en-US" xlink:label="lab_us-gaap_PaymentsOfDividendsCommonStock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payments of Ordinary Dividends, Common Stock</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsOfDividendsCommonStock" xlink:to="lab_us-gaap_PaymentsOfDividendsCommonStock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions_019d1bac-cbe9-720e-88d6-ea8b2da3c8ba_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net investment income</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Ordinary Income, Percent Of Total Distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Ordinary Income, Percent Of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:to="lab_fsk_InvestmentCompanyDistributionOrdinaryIncomePercentOfTotalDistributions" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember_019d9fd9-3aef-7993-9398-aa0db22309b5_terseLabel_en-US" xlink:label="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Senior Floating Rate Loans</link:label>
    <link:label id="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember_label_en-US" xlink:label="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Senior Floating Rate Loans [Member]</link:label>
    <link:label id="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember_documentation_en-US" xlink:label="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.47% Class A-1 Senior Floating Rate Loans</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:href="fsk-20260331.xsd#fsk_A1.47ClassA1SeniorFloatingRateLoansMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:to="lab_fsk_A1.47ClassA1SeniorFloatingRateLoansMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityDomain_019d1bac-cc86-758d-ad8a-c6931d532f71_terseLabel_en-US" xlink:label="lab_dei_EntityDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity [Domain]</link:label>
    <link:label id="lab_dei_EntityDomain_label_en-US" xlink:label="lab_dei_EntityDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityDomain" xlink:to="lab_dei_EntityDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember_terseLabel_en-US" xlink:label="lab_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table</link:label>
    <link:label id="lab_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember_label_en-US" xlink:label="lab_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember" xlink:to="lab_ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestPaidNet_019d1bac-cc86-7bfc-871a-b6fec638bc8b_terseLabel_en-US" xlink:label="lab_us-gaap_InterestPaidNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest paid during the period</link:label>
    <link:label id="lab_us-gaap_InterestPaidNet_label_en-US" xlink:label="lab_us-gaap_InterestPaidNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Paid, Excluding Capitalized Interest, Operating Activity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPaidNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestPaidNet" xlink:to="lab_us-gaap_InterestPaidNet" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentFiscalYearFocus_019d1bac-cc86-70db-b2ff-5f36fa336758_terseLabel_en-US" xlink:label="lab_dei_DocumentFiscalYearFocus" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Fiscal Year Focus</link:label>
    <link:label id="lab_dei_DocumentFiscalYearFocus_label_en-US" xlink:label="lab_dei_DocumentFiscalYearFocus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Fiscal Year Focus</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentFiscalYearFocus" xlink:to="lab_dei_DocumentFiscalYearFocus" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_BasisOfAccountingPolicyPolicyTextBlock_019d1bac-cc86-79b3-81e8-85a5cb46eae8_terseLabel_en-US" xlink:label="lab_us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Basis of Presentation</link:label>
    <link:label id="lab_us-gaap_BasisOfAccountingPolicyPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Basis of Accounting, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="lab_us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock_terseLabel_en-US" xlink:label="lab_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Forgone Recovery, Explanation of Impracticability</link:label>
    <link:label id="lab_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock_label_en-US" xlink:label="lab_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forgone Recovery, Explanation of Impracticability [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock" xlink:to="lab_ecd_ForgoneRecoveryExplanationOfImpracticabilityTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RepaymentsOfLongTermDebt_019d1bac-ccf8-7e04-9739-3257ab8837c6_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_RepaymentsOfLongTermDebt" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Repayments of financing arrangements</link:label>
    <link:label id="lab_us-gaap_RepaymentsOfLongTermDebt_label_en-US" xlink:label="lab_us-gaap_RepaymentsOfLongTermDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Repayments of Long-Term Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RepaymentsOfLongTermDebt" xlink:to="lab_us-gaap_RepaymentsOfLongTermDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityInteractiveDataCurrent_019d1bac-ccf8-7138-bc24-b392c1f82a90_terseLabel_en-US" xlink:label="lab_dei_EntityInteractiveDataCurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Interactive Data Current</link:label>
    <link:label id="lab_dei_EntityInteractiveDataCurrent_label_en-US" xlink:label="lab_dei_EntityInteractiveDataCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Interactive Data Current</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityInteractiveDataCurrent" xlink:to="lab_dei_EntityInteractiveDataCurrent" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyCommittedCapital_019d1bac-cc86-7967-82c2-6e393b34ff43_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyCommittedCapital" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate credit opportunities partners</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyCommittedCapital_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyCommittedCapital" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyCommittedCapital" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyCommittedCapital"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyCommittedCapital" xlink:to="lab_us-gaap_InvestmentCompanyCommittedCapital" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember_019d689a-2a6b-7fb5-a25c-9aa5beba1a2d_verboseLabel_en-US" xlink:label="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Other Senior Secured Debt</link:label>
    <link:label id="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember_019d1bac-cbe9-7397-8279-f9f16174ed50_terseLabel_en-US" xlink:label="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Senior Secured Debt</link:label>
    <link:label id="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember_label_en-US" xlink:label="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Securities, Other Senior Secured Debt [Member]</link:label>
    <link:label id="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember_documentation_en-US" xlink:label="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Securities, Other Senior Secured Debt [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:href="fsk-20260331.xsd#fsk_DebtSecuritiesOtherSeniorSecuredDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:to="lab_fsk_DebtSecuritiesOtherSeniorSecuredDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember_019d8f02-a450-705d-bf61-58f1fbff4fbc_verboseLabel_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">CLO-3 Notes</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember_019d1bac-cc86-7644-8d57-bba2d06f5ef9_terseLabel_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">CLO-2 Notes</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember_label_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligation Unsecured Notes One [Member]</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember_documentation_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligation Unsecured Notes One</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:href="fsk-20260331.xsd#fsk_CollateralizedLoanObligationUnsecuredNotesOneMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:to="lab_fsk_CollateralizedLoanObligationUnsecuredNotesOneMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.48ClassA1WNotesOutstandingMember_019d1bac-cc86-704f-99ba-b1fe2837f8b0_terseLabel_en-US" xlink:label="lab_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.48% Class A-1W Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.48ClassA1WNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.48% Class A-1W Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.48ClassA1WNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.48% Class A-1W Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.48ClassA1WNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:to="lab_fsk_A1.48ClassA1WNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_GreaterThanGrossBorrowingBaseMember_019e0885-1396-7a0c-81f7-24c122ca6257_terseLabel_en-US" xlink:label="lab_fsk_GreaterThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Greater Than Gross Borrowing Base</link:label>
    <link:label id="lab_fsk_GreaterThanGrossBorrowingBaseMember_label_en-US" xlink:label="lab_fsk_GreaterThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Greater Than Gross Borrowing Base [Member]</link:label>
    <link:label id="lab_fsk_GreaterThanGrossBorrowingBaseMember_documentation_en-US" xlink:label="lab_fsk_GreaterThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Greater Than Gross Borrowing Base</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_GreaterThanGrossBorrowingBaseMember" xlink:href="fsk-20260331.xsd#fsk_GreaterThanGrossBorrowingBaseMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_GreaterThanGrossBorrowingBaseMember" xlink:to="lab_fsk_GreaterThanGrossBorrowingBaseMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DeferredTaxAssetsValuationAllowance_019d1bac-cc86-78e5-a6f1-aae19349a02f_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredTaxAssetsValuationAllowance" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred tax asset offset by valuation allowance</link:label>
    <link:label id="lab_us-gaap_DeferredTaxAssetsValuationAllowance_label_en-US" xlink:label="lab_us-gaap_DeferredTaxAssetsValuationAllowance" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Tax Assets, Valuation Allowance</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DeferredTaxAssetsValuationAllowance" xlink:to="lab_us-gaap_DeferredTaxAssetsValuationAllowance" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward_019d1bac-cbe9-7f37-b1a0-e0875efe08cf_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital loss carryforwards</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distributable Earnings (Loss), Accumulated Capital Loss Carryforward</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward" xlink:to="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EquityAbstract_label_en-US" xlink:label="lab_us-gaap_EquityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EquityAbstract" xlink:to="lab_us-gaap_EquityAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock_019d1bac-cc86-77bb-9b2c-0dc4dffc86a8_terseLabel_en-US" xlink:label="lab_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revenue Recognition</link:label>
    <link:label id="lab_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenue from Contract with Customer [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock" xlink:to="lab_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativesPolicyTextBlock_019d1bac-cc86-74b9-aa3d-c4b4abeb6650_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativesPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Instruments</link:label>
    <link:label id="lab_us-gaap_DerivativesPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_DerivativesPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivatives, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativesPolicyTextBlock" xlink:to="lab_us-gaap_DerivativesPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SegmentReportingDisclosureTextBlock_019d1bac-cbe9-705b-8f16-15253e1315ae_terseLabel_en-US" xlink:label="lab_us-gaap_SegmentReportingDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Segment Reporting</link:label>
    <link:label id="lab_us-gaap_SegmentReportingDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_SegmentReportingDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Segment Reporting Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SegmentReportingDisclosureTextBlock" xlink:to="lab_us-gaap_SegmentReportingDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentOwnedAtCost_019d1bac-cc86-703c-bc63-cd61becb8f95_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtCost" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Investment owned, cost</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtCost_019d1bac-cc86-78cb-84a4-76037b81c4a7_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtCost" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Notional Amount</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtCost_019d1bac-cc86-7bb9-850b-1113074751db_netLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtCost" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Amortized Cost</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedAtCost_label_en-US" xlink:label="lab_us-gaap_InvestmentOwnedAtCost" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtCost" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedAtCost"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentOwnedAtCost" xlink:to="lab_us-gaap_InvestmentOwnedAtCost" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019d1bac-cc86-70f5-b9d5-42d6e738e54c_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_GainLossOnSaleOfDerivatives_019d1bac-cbe9-7946-85d5-b80d6868e3db_terseLabel_en-US" xlink:label="lab_us-gaap_GainLossOnSaleOfDerivatives" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_GainLossOnSaleOfDerivatives_019d68de-60c9-7f6c-a7fa-7a7663bf9e64_verboseLabel_en-US" xlink:label="lab_us-gaap_GainLossOnSaleOfDerivatives" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_GainLossOnSaleOfDerivatives_label_en-US" xlink:label="lab_us-gaap_GainLossOnSaleOfDerivatives" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gain (Loss) on Sale of Derivatives</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfDerivatives" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfDerivatives"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_GainLossOnSaleOfDerivatives" xlink:to="lab_us-gaap_GainLossOnSaleOfDerivatives" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SaleOfStockSalesCommissionPercent_019d1bac-cc86-79b9-8a33-ada6e34b5624_terseLabel_en-US" xlink:label="lab_fsk_SaleOfStockSalesCommissionPercent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Sale of stock, sales commission (as percent)</link:label>
    <link:label id="lab_fsk_SaleOfStockSalesCommissionPercent_label_en-US" xlink:label="lab_fsk_SaleOfStockSalesCommissionPercent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Sales Commission, Percent</link:label>
    <link:label id="lab_fsk_SaleOfStockSalesCommissionPercent_documentation_en-US" xlink:label="lab_fsk_SaleOfStockSalesCommissionPercent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Sales Commission, Percent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SaleOfStockSalesCommissionPercent" xlink:href="fsk-20260331.xsd#fsk_SaleOfStockSalesCommissionPercent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SaleOfStockSalesCommissionPercent" xlink:to="lab_fsk_SaleOfStockSalesCommissionPercent" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax_019d1bac-cc86-7ebe-9c69-44da9ac4f8bd_terseLabel_en-US" xlink:label="lab_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) on investments, foreign currency forward contracts and foreign currency</link:label>
    <link:label id="lab_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax_label_en-US" xlink:label="lab_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Realized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, after Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax" xlink:to="lab_us-gaap_RealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionPriceChangeOperatingAfterTax" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherCommitmentsLineItems_019d1bac-cbe9-7bbe-8eea-0091083a1af4_terseLabel_en-US" xlink:label="lab_us-gaap_OtherCommitmentsLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Commitments [Line Items]</link:label>
    <link:label id="lab_us-gaap_OtherCommitmentsLineItems_label_en-US" xlink:label="lab_us-gaap_OtherCommitmentsLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Commitments [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherCommitmentsLineItems" xlink:to="lab_us-gaap_OtherCommitmentsLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EquityAndOtherSecuritiesMember_019d1bac-cc86-7326-8116-22ec95524858_terseLabel_en-US" xlink:label="lab_fsk_EquityAndOtherSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity And Other Securities</link:label>
    <link:label id="lab_fsk_EquityAndOtherSecuritiesMember_label_en-US" xlink:label="lab_fsk_EquityAndOtherSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity And Other Securities [Member]</link:label>
    <link:label id="lab_fsk_EquityAndOtherSecuritiesMember_documentation_en-US" xlink:label="lab_fsk_EquityAndOtherSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Equity And Other Securities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EquityAndOtherSecuritiesMember" xlink:href="fsk-20260331.xsd#fsk_EquityAndOtherSecuritiesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EquityAndOtherSecuritiesMember" xlink:to="lab_fsk_EquityAndOtherSecuritiesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Total Shareholder Return</link:label>
    <link:label id="lab_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock_label_en-US" xlink:label="lab_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Total Shareholder Return [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock" xlink:to="lab_ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_WeightedAverageMember_019d1bac-cc86-7929-99dc-79245af34580_terseLabel_en-US" xlink:label="lab_srt_WeightedAverageMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted Average</link:label>
    <link:label id="lab_srt_WeightedAverageMember_label_en-US" xlink:label="lab_srt_WeightedAverageMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted Average [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_WeightedAverageMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_WeightedAverageMember" xlink:to="lab_srt_WeightedAverageMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019d1bac-cc86-7519-8b09-223787aa15a8_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value, Recurring and Nonrecurring [Table]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Recurring and Nonrecurring [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_HouseholdPersonalProductsSectorMember_019d1bac-cc86-71fe-ac72-5be432d6823c_terseLabel_en-US" xlink:label="lab_fsk_HouseholdPersonalProductsSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Household &amp; Personal Products</link:label>
    <link:label id="lab_fsk_HouseholdPersonalProductsSectorMember_label_en-US" xlink:label="lab_fsk_HouseholdPersonalProductsSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Household &amp; Personal Products Sector [Member]</link:label>
    <link:label id="lab_fsk_HouseholdPersonalProductsSectorMember_documentation_en-US" xlink:label="lab_fsk_HouseholdPersonalProductsSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Household &amp; Personal Products Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_HouseholdPersonalProductsSectorMember" xlink:href="fsk-20260331.xsd#fsk_HouseholdPersonalProductsSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_HouseholdPersonalProductsSectorMember" xlink:to="lab_fsk_HouseholdPersonalProductsSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture_019d1bac-cc86-78e2-a8d8-a7a28ba9d022_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amount funded to joint venture</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture_label_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Funded To Joint Venture</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Funded To Joint Venture</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:to="lab_fsk_InvestmentCompanyCommittedCapitalFundedToJointVenture" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockRepurchasedDuringPeriodValue_019d1bac-cc86-7224-ba08-f83a72651fc3_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_StockRepurchasedDuringPeriodValue" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Repurchases of common stock</link:label>
    <link:label id="lab_us-gaap_StockRepurchasedDuringPeriodValue_label_en-US" xlink:label="lab_us-gaap_StockRepurchasedDuringPeriodValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Repurchased During Period, Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockRepurchasedDuringPeriodValue" xlink:to="lab_us-gaap_StockRepurchasedDuringPeriodValue" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AmblerCreditFacilityMember_019d1bac-ccf8-7354-9d3c-5624b97aff10_terseLabel_en-US" xlink:label="lab_fsk_AmblerCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ambler Credit Facility</link:label>
    <link:label id="lab_fsk_AmblerCreditFacilityMember_label_en-US" xlink:label="lab_fsk_AmblerCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Ambler Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_AmblerCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_AmblerCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Ambler Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AmblerCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_AmblerCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AmblerCreditFacilityMember" xlink:to="lab_fsk_AmblerCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax_019d1bac-cc86-7520-904e-ab29763cab1e_terseLabel_en-US" xlink:label="lab_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized appreciation (depreciation) on investments and foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax_label_en-US" xlink:label="lab_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Gain (Loss), Investment and Derivative, Operating, after Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax" xlink:to="lab_us-gaap_UnrealizedGainLossInvestmentAndDerivativeOperatingAfterTax" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetAssetValuePerShare_019d1bac-ccf8-7454-90c6-29ca1e913e9f_terseLabel_en-US" xlink:label="lab_us-gaap_NetAssetValuePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net asset value per share of common stock at period end (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_NetAssetValuePerShare_019d1bac-ccf8-7513-92ee-8dc8705ce8ad_periodStartLabel_en-US" xlink:label="lab_us-gaap_NetAssetValuePerShare" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Net asset value, beginning of period (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_NetAssetValuePerShare_019d1bac-ccf8-728d-93b0-785b59bc1d1c_periodEndLabel_en-US" xlink:label="lab_us-gaap_NetAssetValuePerShare" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Net asset value, end of period (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_NetAssetValuePerShare_label_en-US" xlink:label="lab_us-gaap_NetAssetValuePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Asset Value Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetAssetValuePerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetAssetValuePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetAssetValuePerShare" xlink:to="lab_us-gaap_NetAssetValuePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityCentralIndexKey_019d1bac-cc86-7ef7-94ab-e36da543aa40_terseLabel_en-US" xlink:label="lab_dei_EntityCentralIndexKey" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Central Index Key</link:label>
    <link:label id="lab_dei_EntityCentralIndexKey_label_en-US" xlink:label="lab_dei_EntityCentralIndexKey" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Central Index Key</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityCentralIndexKey" xlink:to="lab_dei_EntityCentralIndexKey" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeoName_terseLabel_en-US" xlink:label="lab_ecd_PeoName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">PEO Name</link:label>
    <link:label id="lab_ecd_PeoName_label_en-US" xlink:label="lab_ecd_PeoName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">PEO Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeoName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeoName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeoName" xlink:to="lab_ecd_PeoName" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember_019d1bac-ccf8-7ffa-bab6-5dae425f23ad_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly Catch-up Threshold</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly Catch-up Threshold [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Quarterly Catch-up Threshold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_019e1484-944e-796d-8481-5bfff16b13ef_terseLabel_en-US" xlink:label="lab_us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Tender offer amount</link:label>
    <link:label id="lab_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_label_en-US" xlink:label="lab_us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of Stock, Consideration Received on Transaction</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:to="lab_us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember_terseLabel_en-US" xlink:label="lab_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year</link:label>
    <link:label id="lab_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember_label_en-US" xlink:label="lab_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember" xlink:to="lab_ecd_FrValAsOfPrrYrEndOfEqtyAwrdsGrntdInPrrYrsFldVstngCondsDrngCvrdYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare_019d1bac-cc86-7972-b0e5-431a312bd5d2_terseLabel_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average cost per share of stock repurchased and distributed (in dollars per share)</link:label>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare_label_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Dividend Reinvestment Plan, Average Cost Per Share</link:label>
    <link:label id="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare_documentation_en-US" xlink:label="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Dividend Reinvestment Plan, Average Cost Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:href="fsk-20260331.xsd#fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:to="lab_fsk_StockIssuedDuringPeriodDividendReinvestmentPlanAverageCostPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_OutstandingAggtErrCompAmt_terseLabel_en-US" xlink:label="lab_ecd_OutstandingAggtErrCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Outstanding Aggregate Erroneous Compensation Amount</link:label>
    <link:label id="lab_ecd_OutstandingAggtErrCompAmt_label_en-US" xlink:label="lab_ecd_OutstandingAggtErrCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Aggregate Erroneous Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_OutstandingAggtErrCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_OutstandingAggtErrCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_OutstandingAggtErrCompAmt" xlink:to="lab_ecd_OutstandingAggtErrCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RevolvingCreditFacilityMember_019daad4-9310-77d7-a52c-c7cce3711f8d_verboseLabel_en-US" xlink:label="lab_us-gaap_RevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Revolving Credit Facility</link:label>
    <link:label id="lab_us-gaap_RevolvingCreditFacilityMember_019d1bac-cc86-7fbc-aa3d-f6f4aaf2f9c1_terseLabel_en-US" xlink:label="lab_us-gaap_RevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revolving Credit Facility</link:label>
    <link:label id="lab_us-gaap_RevolvingCreditFacilityMember_label_en-US" xlink:label="lab_us-gaap_RevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revolving Credit Facility [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RevolvingCreditFacilityMember" xlink:to="lab_us-gaap_RevolvingCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FundedSubordinatedDebtMember_019d1bac-ccf8-7b19-82a3-cae3368a30ef_terseLabel_en-US" xlink:label="lab_fsk_FundedSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Funded, Subordinated Debt</link:label>
    <link:label id="lab_fsk_FundedSubordinatedDebtMember_label_en-US" xlink:label="lab_fsk_FundedSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Funded, Subordinated Debt [Member]</link:label>
    <link:label id="lab_fsk_FundedSubordinatedDebtMember_documentation_en-US" xlink:label="lab_fsk_FundedSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Funded, Subordinated Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FundedSubordinatedDebtMember" xlink:href="fsk-20260331.xsd#fsk_FundedSubordinatedDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FundedSubordinatedDebtMember" xlink:to="lab_fsk_FundedSubordinatedDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrDuration_terseLabel_en-US" xlink:label="lab_ecd_TrdArrDuration" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Arrangement Duration</link:label>
    <link:label id="lab_ecd_TrdArrDuration_label_en-US" xlink:label="lab_ecd_TrdArrDuration" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement Duration</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrDuration" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrDuration"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrDuration" xlink:to="lab_ecd_TrdArrDuration" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsForProceedsFromInvestments_019d1bac-cc86-7d30-812f-6ab4da3c9d2d_terseLabel_en-US" xlink:label="lab_us-gaap_PaymentsForProceedsFromInvestments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Upfront Payments/Receipts</link:label>
    <link:label id="lab_us-gaap_PaymentsForProceedsFromInvestments_label_en-US" xlink:label="lab_us-gaap_PaymentsForProceedsFromInvestments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payments for (Proceeds from) Investments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromInvestments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForProceedsFromInvestments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsForProceedsFromInvestments" xlink:to="lab_us-gaap_PaymentsForProceedsFromInvestments" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.60ClassA2LNotesOutstandingMember_019d1bac-cc86-74b8-a60f-0c81456458c0_terseLabel_en-US" xlink:label="lab_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.60% Class A-2L Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.60ClassA2LNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.60% Class A-2L Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.60ClassA2LNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.60% Class A-2L Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.60ClassA2LNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:to="lab_fsk_A1.60ClassA2LNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock_019d1bac-ccf8-72d6-9a6b-d8b877cdee92_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Fair Value And Balance Sheet Location of Company's Derivative Instruments</link:label>
    <link:label id="lab_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock" xlink:to="lab_us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019d1bac-cc86-7193-970f-0b7cde933793_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">(Increase) decrease in prepaid expenses and other assets</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="lab_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardExrcPrice_terseLabel_en-US" xlink:label="lab_ecd_AwardExrcPrice" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Exercise Price</link:label>
    <link:label id="lab_ecd_AwardExrcPrice_label_en-US" xlink:label="lab_ecd_AwardExrcPrice" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Exercise Price</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardExrcPrice" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardExrcPrice"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardExrcPrice" xlink:to="lab_ecd_AwardExrcPrice" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityFilerCategory_019d1bac-cbe9-767b-acff-025c49ab5625_terseLabel_en-US" xlink:label="lab_dei_EntityFilerCategory" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Filer Category</link:label>
    <link:label id="lab_dei_EntityFilerCategory_label_en-US" xlink:label="lab_dei_EntityFilerCategory" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Filer Category</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityFilerCategory" xlink:to="lab_dei_EntityFilerCategory" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DividendIncomeOperating_019d1bac-cc86-79c6-b191-b8ace6013b90_terseLabel_en-US" xlink:label="lab_us-gaap_DividendIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Dividend and other income</link:label>
    <link:label id="lab_us-gaap_DividendIncomeOperating_019d1bac-cc86-7066-bd76-8a13ce404742_verboseLabel_en-US" xlink:label="lab_us-gaap_DividendIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Dividend and Other Income</link:label>
    <link:label id="lab_us-gaap_DividendIncomeOperating_label_en-US" xlink:label="lab_us-gaap_DividendIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Dividend Income, Operating</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendIncomeOperating" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendIncomeOperating"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DividendIncomeOperating" xlink:to="lab_us-gaap_DividendIncomeOperating" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_LocalPhoneNumber_019d1bac-cc86-7a1b-8bd6-abcb2837c42b_terseLabel_en-US" xlink:label="lab_dei_LocalPhoneNumber" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Local Phone Number</link:label>
    <link:label id="lab_dei_LocalPhoneNumber_label_en-US" xlink:label="lab_dei_LocalPhoneNumber" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Local Phone Number</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_LocalPhoneNumber" xlink:to="lab_dei_LocalPhoneNumber" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_Additional402vDisclosureTextBlock_terseLabel_en-US" xlink:label="lab_ecd_Additional402vDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Additional 402(v) Disclosure</link:label>
    <link:label id="lab_ecd_Additional402vDisclosureTextBlock_label_en-US" xlink:label="lab_ecd_Additional402vDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional 402(v) Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_Additional402vDisclosureTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_Additional402vDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_Additional402vDisclosureTextBlock" xlink:to="lab_ecd_Additional402vDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventTypeAxis_019d1bac-cc86-7a6d-9531-b83fe8b56fcd_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Axis]</link:label>
    <link:label id="lab_us-gaap_SubsequentEventTypeAxis_label_en-US" xlink:label="lab_us-gaap_SubsequentEventTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventTypeAxis" xlink:to="lab_us-gaap_SubsequentEventTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased_019d1bac-ccf8-7229-b0f9-a2220e12ee31_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in payable for investments purchased</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Payable for Investment Purchased</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased" xlink:to="lab_us-gaap_IncreaseDecreaseInPayableForInvestmentPurchased" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AssetsAbstract_019d1bac-cc86-74fd-9aee-08c949685f3f_terseLabel_en-US" xlink:label="lab_us-gaap_AssetsAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Assets</link:label>
    <link:label id="lab_us-gaap_AssetsAbstract_label_en-US" xlink:label="lab_us-gaap_AssetsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Assets [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="lab_us-gaap_AssetsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CreditFacilityAxis_019d1bac-ccf8-7f17-a60c-21c6ac9a91c2_terseLabel_en-US" xlink:label="lab_us-gaap_CreditFacilityAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Credit Facility [Axis]</link:label>
    <link:label id="lab_us-gaap_CreditFacilityAxis_label_en-US" xlink:label="lab_us-gaap_CreditFacilityAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CreditFacilityAxis" xlink:to="lab_us-gaap_CreditFacilityAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AssetBasedFinanceMember_019d1bac-ccf8-75da-b3c7-d0efb20b5c0d_terseLabel_en-US" xlink:label="lab_fsk_AssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Asset Based Finance</link:label>
    <link:label id="lab_fsk_AssetBasedFinanceMember_019d1bac-ccf8-7d8c-b1a6-f3d553c514d6_verboseLabel_en-US" xlink:label="lab_fsk_AssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Asset Based Finance</link:label>
    <link:label id="lab_fsk_AssetBasedFinanceMember_label_en-US" xlink:label="lab_fsk_AssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Asset Based Finance [Member]</link:label>
    <link:label id="lab_fsk_AssetBasedFinanceMember_documentation_en-US" xlink:label="lab_fsk_AssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Asset Based Finance [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AssetBasedFinanceMember" xlink:href="fsk-20260331.xsd#fsk_AssetBasedFinanceMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AssetBasedFinanceMember" xlink:to="lab_fsk_AssetBasedFinanceMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_019d1bac-cc86-71c8-80ec-1468e270bb25_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross Additions</link:label>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_label_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments in and Advances to Affiliates, at Fair Value, Gross Additions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:to="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_UndrlygSecurityMktPriceChngPct_terseLabel_en-US" xlink:label="lab_ecd_UndrlygSecurityMktPriceChngPct" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Underlying Security Market Price Change</link:label>
    <link:label id="lab_ecd_UndrlygSecurityMktPriceChngPct_label_en-US" xlink:label="lab_ecd_UndrlygSecurityMktPriceChngPct" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Underlying Security Market Price Change, Percent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_UndrlygSecurityMktPriceChngPct" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_UndrlygSecurityMktPriceChngPct"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_UndrlygSecurityMktPriceChngPct" xlink:to="lab_ecd_UndrlygSecurityMktPriceChngPct" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_BalanceSheetLocationAxis_019d6645-3238-78b7-a7a6-42cb6687787a_terseLabel_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statement of Financial Position Location, Balance [Axis]</link:label>
    <link:label id="lab_us-gaap_BalanceSheetLocationAxis_label_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position Location, Balance [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_BalanceSheetLocationAxis" xlink:to="lab_us-gaap_BalanceSheetLocationAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentAxis_019d1bac-cc86-7a82-bf32-e3ee18664356_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument [Axis]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentAxis_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentAxis" xlink:to="lab_us-gaap_DebtInstrumentAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution_019d1bac-ccf8-795e-a0ce-753353434ec1_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Return of capital</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Tax Return of Capital Distribution</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution" xlink:to="lab_us-gaap_InvestmentCompanyTaxReturnOfCapitalDistribution" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueDisclosuresTextBlock_019d1bac-ccf8-73b8-9be0-768a54ec1a13_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueDisclosuresTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value of Financial Instruments</link:label>
    <link:label id="lab_us-gaap_FairValueDisclosuresTextBlock_label_en-US" xlink:label="lab_us-gaap_FairValueDisclosuresTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Disclosures [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosuresTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueDisclosuresTextBlock" xlink:to="lab_us-gaap_FairValueDisclosuresTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance_019e14aa-c102-7161-84ee-15e3953be98e_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Issuer option, period to redeem all outstanding shares</link:label>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance_label_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Issuer Option, Required Redemption For Cash, Period After Issuance</link:label>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance_documentation_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Issuer Option, Required Redemption For Cash, Period After Issuance</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:href="fsk-20260331.xsd#fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:to="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashPeriodAfterIssuance" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CreditFacilityDomain_019d1bac-cc86-7881-8ead-5d2cd3321aeb_terseLabel_en-US" xlink:label="lab_us-gaap_CreditFacilityDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Credit Facility [Domain]</link:label>
    <link:label id="lab_us-gaap_CreditFacilityDomain_label_en-US" xlink:label="lab_us-gaap_CreditFacilityDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CreditFacilityDomain" xlink:to="lab_us-gaap_CreditFacilityDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019d1bac-cc86-71be-95bd-7fb9b873b1f1_terseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized appreciation (depreciation) on investments:</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019d1bac-cc86-7f9f-9c36-719ec5c7faa6_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized (appreciation) depreciation on investments</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_019d1bac-cc86-7815-9a17-c93f4a75a29d_verboseLabel_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net Change in Unrealized Appreciation (Depreciation)</link:label>
    <link:label id="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_label_en-US" xlink:label="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Unrealized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:to="lab_us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockholdersEquityAbstract_019d1bac-cc86-7202-9416-dcbcce05dd15_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stockholders&#8217; equity</link:label>
    <link:label id="lab_us-gaap_StockholdersEquityAbstract_label_en-US" xlink:label="lab_us-gaap_StockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity, Attributable to Parent [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockholdersEquityAbstract" xlink:to="lab_us-gaap_StockholdersEquityAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember_terseLabel_en-US" xlink:label="lab_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year</link:label>
    <link:label id="lab_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember_label_en-US" xlink:label="lab_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember" xlink:to="lab_ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentOwnedPercentOfNetAssets_019d1bac-cc86-7092-872c-d80d48f8073c_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percent of net assets</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedPercentOfNetAssets_label_en-US" xlink:label="lab_us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, Net Assets, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedPercentOfNetAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:to="lab_us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityAddressAddressLine1_019d1bac-ccf8-7f84-8c05-2466523c0ae5_terseLabel_en-US" xlink:label="lab_dei_EntityAddressAddressLine1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Address, Address Line One</link:label>
    <link:label id="lab_dei_EntityAddressAddressLine1_label_en-US" xlink:label="lab_dei_EntityAddressAddressLine1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Address, Address Line One</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressAddressLine1" xlink:to="lab_dei_EntityAddressAddressLine1" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityAddressAddressLine2_019e07e6-31a9-7abe-85e1-fd8e514e5257_terseLabel_en-US" xlink:label="lab_dei_EntityAddressAddressLine2" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Address, Address Line Two</link:label>
    <link:label id="lab_dei_EntityAddressAddressLine2_label_en-US" xlink:label="lab_dei_EntityAddressAddressLine2" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Address, Address Line Two</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressAddressLine2" xlink:to="lab_dei_EntityAddressAddressLine2" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TreasuryStockValueAcquiredCostMethod_019d1bac-cc86-7797-b563-40551c85ddbe_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Share Repurchase Program</link:label>
    <link:label id="lab_us-gaap_TreasuryStockValueAcquiredCostMethod_label_en-US" xlink:label="lab_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Treasury Stock, Value, Acquired, Cost Method</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:to="lab_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentInterestRateStatedPercentage_019d1bac-cc86-723d-9791-b8682e18de7f_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stated interest rate (as percent)</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentInterestRateStatedPercentage_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Interest Rate, Stated Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="lab_us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_019d1bac-cc86-7e87-b4ab-227fe1b50c5e_terseLabel_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized appreciation</link:label>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation_label_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Tax Basis, Unrealized Gain</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation" xlink:to="lab_us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentTypeCategorizationMember_019d1bac-cc86-7ca6-9be9-d6883da928ca_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentTypeCategorizationMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments [Domain]</link:label>
    <link:label id="lab_us-gaap_InvestmentTypeCategorizationMember_label_en-US" xlink:label="lab_us-gaap_InvestmentTypeCategorizationMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember" xlink:to="lab_us-gaap_InvestmentTypeCategorizationMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ManagementAndServiceFeesBaseRate_019d1bac-cc86-7d12-bc47-4895541539bb_terseLabel_en-US" xlink:label="lab_us-gaap_ManagementAndServiceFeesBaseRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Management and service fees, base rate</link:label>
    <link:label id="lab_us-gaap_ManagementAndServiceFeesBaseRate_label_en-US" xlink:label="lab_us-gaap_ManagementAndServiceFeesBaseRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Management and Service Fees, Base Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementAndServiceFeesBaseRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementAndServiceFeesBaseRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ManagementAndServiceFeesBaseRate" xlink:to="lab_us-gaap_ManagementAndServiceFeesBaseRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable_019d1bac-cc86-7d9a-b280-3f739b3b9933_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Support for Nonconsolidated Legal Entity [Table]</link:label>
    <link:label id="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable_label_en-US" xlink:label="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Support for Nonconsolidated Legal Entity [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable" xlink:to="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_019d1bac-cc86-7563-8967-9df9c1716b40_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Instruments</link:label>
    <link:label id="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instruments and Hedging Activities Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:to="lab_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EquitySecuritiesByIndustryAxis_019d1bac-cc86-7673-b147-eb3b831cc593_terseLabel_en-US" xlink:label="lab_us-gaap_EquitySecuritiesByIndustryAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Industry Sector [Axis]</link:label>
    <link:label id="lab_us-gaap_EquitySecuritiesByIndustryAxis_label_en-US" xlink:label="lab_us-gaap_EquitySecuritiesByIndustryAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Industry Sector [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesByIndustryAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesByIndustryAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EquitySecuritiesByIndustryAxis" xlink:to="lab_us-gaap_EquitySecuritiesByIndustryAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfStockByClassTextBlock_019d1bac-cbe9-71cf-989d-2514a17b31bf_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Common Stock Transactions</link:label>
    <link:label id="lab_us-gaap_ScheduleOfStockByClassTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Stock by Class [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfStockByClassTextBlock" xlink:to="lab_us-gaap_ScheduleOfStockByClassTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ManagementFeePayable_019d1bac-cbe9-79b3-902b-e088aa4a8325_terseLabel_en-US" xlink:label="lab_us-gaap_ManagementFeePayable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Management fees payable</link:label>
    <link:label id="lab_us-gaap_ManagementFeePayable_label_en-US" xlink:label="lab_us-gaap_ManagementFeePayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Management Fee Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementFeePayable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementFeePayable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ManagementFeePayable" xlink:to="lab_us-gaap_ManagementFeePayable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAsset_019d1bac-cc86-78b8-9704-c80540ce6f0c_verboseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Unrealized appreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAsset_019d1bac-cc86-7625-a208-b960f4e5eb04_netLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Derivative Assets Subject to Master Netting Agreement</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAsset_019d1bac-cc86-76c6-a5a0-e05e1db5e10c_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross Amount of Recognized Assets</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAsset_label_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Subject to Master Netting Arrangement, before Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:to="lab_us-gaap_DerivativeFairValueOfDerivativeAsset" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyAbstract_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyAbstract" xlink:to="lab_us-gaap_InvestmentCompanyAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_019d1bac-cbe9-7092-b0aa-e8fff3bf63ba_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Highlights</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Highlights [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:to="lab_us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InterestRateSwapFiveMember_019d1bac-cc86-716e-a706-f436a0168ab5_terseLabel_en-US" xlink:label="lab_fsk_InterestRateSwapFiveMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Five</link:label>
    <link:label id="lab_fsk_InterestRateSwapFiveMember_label_en-US" xlink:label="lab_fsk_InterestRateSwapFiveMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Five [Member]</link:label>
    <link:label id="lab_fsk_InterestRateSwapFiveMember_documentation_en-US" xlink:label="lab_fsk_InterestRateSwapFiveMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Five</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InterestRateSwapFiveMember" xlink:href="fsk-20260331.xsd#fsk_InterestRateSwapFiveMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InterestRateSwapFiveMember" xlink:to="lab_fsk_InterestRateSwapFiveMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardGrantDateFairValue_terseLabel_en-US" xlink:label="lab_ecd_AwardGrantDateFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value as of Grant Date</link:label>
    <link:label id="lab_ecd_AwardGrantDateFairValue_label_en-US" xlink:label="lab_ecd_AwardGrantDateFairValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Grant Date Fair Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardGrantDateFairValue" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardGrantDateFairValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardGrantDateFairValue" xlink:to="lab_ecd_AwardGrantDateFairValue" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityRegistrantName_019d1bac-cbe9-7439-86c9-7106b7f3e26e_terseLabel_en-US" xlink:label="lab_dei_EntityRegistrantName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Registrant Name</link:label>
    <link:label id="lab_dei_EntityRegistrantName_label_en-US" xlink:label="lab_dei_EntityRegistrantName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Registrant Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityRegistrantName" xlink:to="lab_dei_EntityRegistrantName" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_StkPrcOrTsrEstimationMethodTextBlock_terseLabel_en-US" xlink:label="lab_ecd_StkPrcOrTsrEstimationMethodTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Price or TSR Estimation Method</link:label>
    <link:label id="lab_ecd_StkPrcOrTsrEstimationMethodTextBlock_label_en-US" xlink:label="lab_ecd_StkPrcOrTsrEstimationMethodTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Price or TSR Estimation Method [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_StkPrcOrTsrEstimationMethodTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_StkPrcOrTsrEstimationMethodTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_StkPrcOrTsrEstimationMethodTextBlock" xlink:to="lab_ecd_StkPrcOrTsrEstimationMethodTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SterlingOvernightIndexAverageMember_019d1bac-cc86-71e7-8726-28f829fa19bd_terseLabel_en-US" xlink:label="lab_fsk_SterlingOvernightIndexAverageMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">SONIA</link:label>
    <link:label id="lab_fsk_SterlingOvernightIndexAverageMember_label_en-US" xlink:label="lab_fsk_SterlingOvernightIndexAverageMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sterling Overnight Index Average [Member]</link:label>
    <link:label id="lab_fsk_SterlingOvernightIndexAverageMember_documentation_en-US" xlink:label="lab_fsk_SterlingOvernightIndexAverageMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Sterling Overnight Index Average</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SterlingOvernightIndexAverageMember" xlink:href="fsk-20260331.xsd#fsk_SterlingOvernightIndexAverageMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SterlingOvernightIndexAverageMember" xlink:to="lab_fsk_SterlingOvernightIndexAverageMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementMember_019d1bac-cbe9-7d65-9ab1-4222ea4e20d8_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare_019d1bac-cc86-7e4c-ae9b-dbf137ba25ab_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Repurchases of common stock (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Share Repurchase, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare" xlink:to="lab_us-gaap_InvestmentCompanyRepurchaseOfSharesPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember_019d1bac-cc86-701d-b769-7827b407637f_terseLabel_en-US" xlink:label="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Senior Secured Revolving Credit Facility</link:label>
    <link:label id="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember_label_en-US" xlink:label="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior Secured Revolving Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Senior Secured Revolving Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_SeniorSecuredRevolvingCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:to="lab_fsk_SeniorSecuredRevolvingCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ValuationWaterfallApproachMember_019d1bac-cbe9-73fc-aca6-fcb7ebd6a668_terseLabel_en-US" xlink:label="lab_fsk_ValuationWaterfallApproachMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Waterfall</link:label>
    <link:label id="lab_fsk_ValuationWaterfallApproachMember_label_en-US" xlink:label="lab_fsk_ValuationWaterfallApproachMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation, Waterfall Approach [Member]</link:label>
    <link:label id="lab_fsk_ValuationWaterfallApproachMember_documentation_en-US" xlink:label="lab_fsk_ValuationWaterfallApproachMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Valuation, Waterfall Approach [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ValuationWaterfallApproachMember" xlink:href="fsk-20260331.xsd#fsk_ValuationWaterfallApproachMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ValuationWaterfallApproachMember" xlink:to="lab_fsk_ValuationWaterfallApproachMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentForIncentiveFee_019d1bac-cc86-73fd-86f4-87e66594a81e_terseLabel_en-US" xlink:label="lab_us-gaap_PaymentForIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Incentive fee paid</link:label>
    <link:label id="lab_us-gaap_PaymentForIncentiveFee_label_en-US" xlink:label="lab_us-gaap_PaymentForIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payment for Incentive Fee</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForIncentiveFee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentForIncentiveFee"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentForIncentiveFee" xlink:to="lab_us-gaap_PaymentForIncentiveFee" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays_019e14b8-8f2a-7517-a002-98c455770854_terseLabel_en-US" xlink:label="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of trading days</link:label>
    <link:label id="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays_label_en-US" xlink:label="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Common Stock, NYSE Minimum Price, Number Of Trading Days</link:label>
    <link:label id="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays_documentation_en-US" xlink:label="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Sale Of Stock, Common Stock, NYSE Minimum Price, Number Of Trading Days</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:href="fsk-20260331.xsd#fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:to="lab_fsk_SaleOfStockCommonStockNYSEMinimumPriceNumberOfTradingDays" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionLineItems_019d1bac-cc86-727b-a73b-143bc92b230c_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Line Items]</link:label>
    <link:label id="lab_us-gaap_RelatedPartyTransactionLineItems_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems" xlink:to="lab_us-gaap_RelatedPartyTransactionLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentQuarterlyReport_019d1bac-ccf8-700d-83e7-97484671c8ca_terseLabel_en-US" xlink:label="lab_dei_DocumentQuarterlyReport" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Quarterly Report</link:label>
    <link:label id="lab_dei_DocumentQuarterlyReport_label_en-US" xlink:label="lab_dei_DocumentQuarterlyReport" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Quarterly Report</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentQuarterlyReport"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentQuarterlyReport" xlink:to="lab_dei_DocumentQuarterlyReport" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor_019e0716-1036-70a2-a734-df9367d3b2ca_terseLabel_en-US" xlink:label="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Minimum shareholders' equity amount of net asset value</link:label>
    <link:label id="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor_label_en-US" xlink:label="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Covenant, Minimum Shareholders' Equity Floor</link:label>
    <link:label id="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor_documentation_en-US" xlink:label="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Instrument, Covenant, Minimum Shareholders' Equity Floor</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:href="fsk-20260331.xsd#fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:to="lab_fsk_DebtInstrumentCovenantMinimumShareholdersEquityFloor" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_019d1bac-cc86-73fa-b4e9-08492ac5af9b_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Gross Reductions</link:label>
    <link:label id="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_label_en-US" xlink:label="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments in and Advances to Affiliates, at Fair Value, Gross Reductions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:to="lab_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract_019d1bac-cc86-7fb3-bae3-43f122bbf518_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital share transactions</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Capital Share Transaction, Increase (Decrease) [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract" xlink:to="lab_us-gaap_InvestmentCompanyCapitalShareTransactionsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongTermDebtFairValue_019d1bac-cc86-74e1-9202-d92a18b6b8c8_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebtFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair value</link:label>
    <link:label id="lab_us-gaap_LongTermDebtFairValue_label_en-US" xlink:label="lab_us-gaap_LongTermDebtFairValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Fair Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebtFairValue" xlink:to="lab_us-gaap_LongTermDebtFairValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_019d1bac-cc86-785c-ace6-72b5ac66e836_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Valuation Techniques and Significant Unobservable Inputs Used in Recurring Level 3 Fair Value</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:to="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ChangedPeerGroupFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_ChangedPeerGroupFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Changed Peer Group, Footnote</link:label>
    <link:label id="lab_ecd_ChangedPeerGroupFnTextBlock_label_en-US" xlink:label="lab_ecd_ChangedPeerGroupFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Changed Peer Group, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ChangedPeerGroupFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ChangedPeerGroupFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ChangedPeerGroupFnTextBlock" xlink:to="lab_ecd_ChangedPeerGroupFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_RepurchaseAgreementCounterpartyNameDomain_019d1bac-ccf8-7dfa-b277-26f03c5edbd2_terseLabel_en-US" xlink:label="lab_srt_RepurchaseAgreementCounterpartyNameDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Counterparty Name [Domain]</link:label>
    <link:label id="lab_srt_RepurchaseAgreementCounterpartyNameDomain_label_en-US" xlink:label="lab_srt_RepurchaseAgreementCounterpartyNameDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Counterparty Name [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="lab_srt_RepurchaseAgreementCounterpartyNameDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NumberOfOperatingSegments_019d1bac-cc86-70d5-bae5-01d711e9c976_terseLabel_en-US" xlink:label="lab_us-gaap_NumberOfOperatingSegments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of operating segments</link:label>
    <link:label id="lab_us-gaap_NumberOfOperatingSegments_label_en-US" xlink:label="lab_us-gaap_NumberOfOperatingSegments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number of Operating Segments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NumberOfOperatingSegments" xlink:to="lab_us-gaap_NumberOfOperatingSegments" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InterestRateSwapTwoMember_019d1bac-cc86-7326-a881-c6090f4cdacc_terseLabel_en-US" xlink:label="lab_fsk_InterestRateSwapTwoMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Two</link:label>
    <link:label id="lab_fsk_InterestRateSwapTwoMember_label_en-US" xlink:label="lab_fsk_InterestRateSwapTwoMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Two [Member]</link:label>
    <link:label id="lab_fsk_InterestRateSwapTwoMember_documentation_en-US" xlink:label="lab_fsk_InterestRateSwapTwoMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Two</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InterestRateSwapTwoMember" xlink:href="fsk-20260331.xsd#fsk_InterestRateSwapTwoMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InterestRateSwapTwoMember" xlink:to="lab_fsk_InterestRateSwapTwoMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019d1bac-cc86-71c2-9135-54993771fcd9_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Accretion of discount</link:label>
    <link:label id="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_019d1bac-cc86-72c2-8602-58926b1f76c7_terseLabel_en-US" xlink:label="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accretion of discount (amortization of premium)</link:label>
    <link:label id="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_label_en-US" xlink:label="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accretion (Amortization) of Discounts and Premiums, Investments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:to="lab_us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AdjToPeoCompFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AdjToPeoCompFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustment To PEO Compensation, Footnote</link:label>
    <link:label id="lab_ecd_AdjToPeoCompFnTextBlock_label_en-US" xlink:label="lab_ecd_AdjToPeoCompFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment To PEO Compensation, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AdjToPeoCompFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AdjToPeoCompFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AdjToPeoCompFnTextBlock" xlink:to="lab_ecd_AdjToPeoCompFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract_019d1bac-cc86-7159-82c4-9dc1f0437ae1_terseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operations</link:label>
    <link:label id="lab_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract_label_en-US" xlink:label="lab_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToReportingEntityAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract" xlink:to="lab_us-gaap_NetIncomeLossAttributableToReportingEntityAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember_019d1bac-cc86-73bf-8a44-bf45804fa18f_terseLabel_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Greater Than Or Equal To</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember_label_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Greater Than Or Equal To [Member]</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember_documentation_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Greater Than Or Equal To</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:href="fsk-20260331.xsd#fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:to="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateGreaterThanOrEqualToMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentTypeAxis_019d1bac-cc86-70ec-84fd-26958bc5ff9b_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentTypeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Type [Axis]</link:label>
    <link:label id="lab_us-gaap_InvestmentTypeAxis_label_en-US" xlink:label="lab_us-gaap_InvestmentTypeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Type [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentTypeAxis" xlink:to="lab_us-gaap_InvestmentTypeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019d1bac-cc86-7300-923e-f47abc540978_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party [Axis]</link:label>
    <link:label id="lab_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related and Nonrelated Parties [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="lab_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrIndTitle_terseLabel_en-US" xlink:label="lab_ecd_TrdArrIndTitle" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Title</link:label>
    <link:label id="lab_ecd_TrdArrIndTitle_label_en-US" xlink:label="lab_ecd_TrdArrIndTitle" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement, Individual Title</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrIndTitle" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrIndTitle"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrIndTitle" xlink:to="lab_ecd_TrdArrIndTitle" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeerGroupTotalShareholderRtnAmt_terseLabel_en-US" xlink:label="lab_ecd_PeerGroupTotalShareholderRtnAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Peer Group Total Shareholder Return Amount</link:label>
    <link:label id="lab_ecd_PeerGroupTotalShareholderRtnAmt_label_en-US" xlink:label="lab_ecd_PeerGroupTotalShareholderRtnAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Peer Group Total Shareholder Return Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeerGroupTotalShareholderRtnAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeerGroupTotalShareholderRtnAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeerGroupTotalShareholderRtnAmt" xlink:to="lab_ecd_PeerGroupTotalShareholderRtnAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears_019e14b6-e9de-7b69-a7f1-8f21125e2ebb_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of years that accumulated dividends equals dividends due and unpaid</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears_label_en-US" xlink:label="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Accumulated Dividends Equal To Dividends Due And Unpaid, Number Of Years</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears_documentation_en-US" xlink:label="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Accumulated Dividends Equal To Dividends Due And Unpaid, Number Of Years</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:href="fsk-20260331.xsd#fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:to="lab_fsk_PreferredStockConvertibleAccumulatedDividendsEqualToDividendsDueAndUnpaidNumberOfYears" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract_019d1bac-cc86-75ef-b492-d1fe9ab6cbaf_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stockholder distributions</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract_019d1bac-cc86-784a-98fe-7f0ec94c99e4_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Distribution Amount</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution to Shareholders [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:to="lab_us-gaap_InvestmentCompanyDistributionToShareholdersAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PrepaidExpenseAndOtherAssets_019d1bac-cc86-7b96-b933-4175801a8de5_terseLabel_en-US" xlink:label="lab_us-gaap_PrepaidExpenseAndOtherAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid expenses and other assets</link:label>
    <link:label id="lab_us-gaap_PrepaidExpenseAndOtherAssets_label_en-US" xlink:label="lab_us-gaap_PrepaidExpenseAndOtherAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Prepaid Expense and Other Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssets" xlink:to="lab_us-gaap_PrepaidExpenseAndOtherAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_RestatementDateAxis_terseLabel_en-US" xlink:label="lab_ecd_RestatementDateAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restatement Determination Date:</link:label>
    <link:label id="lab_ecd_RestatementDateAxis_label_en-US" xlink:label="lab_ecd_RestatementDateAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restatement Determination Date [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_RestatementDateAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_RestatementDateAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_RestatementDateAxis" xlink:to="lab_ecd_RestatementDateAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A4250UnsecuredNotesDue2025Member_019d1bac-cc86-7c98-9b67-72d296a146ea_terseLabel_en-US" xlink:label="lab_fsk_A4250UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">4.250% Notes due 2025</link:label>
    <link:label id="lab_fsk_A4250UnsecuredNotesDue2025Member_label_en-US" xlink:label="lab_fsk_A4250UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">4.250% Unsecured Notes due 2025 [Member]</link:label>
    <link:label id="lab_fsk_A4250UnsecuredNotesDue2025Member_documentation_en-US" xlink:label="lab_fsk_A4250UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">4.250% Unsecured Notes due 2025</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A4250UnsecuredNotesDue2025Member" xlink:href="fsk-20260331.xsd#fsk_A4250UnsecuredNotesDue2025Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A4250UnsecuredNotesDue2025Member" xlink:to="lab_fsk_A4250UnsecuredNotesDue2025Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A3125UnsecuredNotesDue2028Member_019d1bac-cc86-7529-9496-d7d240066bf5_terseLabel_en-US" xlink:label="lab_fsk_A3125UnsecuredNotesDue2028Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">3.125% Notes due 2028</link:label>
    <link:label id="lab_fsk_A3125UnsecuredNotesDue2028Member_label_en-US" xlink:label="lab_fsk_A3125UnsecuredNotesDue2028Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">3.125% Unsecured Notes due 2028 [Member]</link:label>
    <link:label id="lab_fsk_A3125UnsecuredNotesDue2028Member_documentation_en-US" xlink:label="lab_fsk_A3125UnsecuredNotesDue2028Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">3.125% Unsecured Notes due 2028</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A3125UnsecuredNotesDue2028Member" xlink:href="fsk-20260331.xsd#fsk_A3125UnsecuredNotesDue2028Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A3125UnsecuredNotesDue2028Member" xlink:to="lab_fsk_A3125UnsecuredNotesDue2028Member" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonPeoNeoMember_terseLabel_en-US" xlink:label="lab_ecd_NonPeoNeoMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-PEO NEO</link:label>
    <link:label id="lab_ecd_NonPeoNeoMember_label_en-US" xlink:label="lab_ecd_NonPeoNeoMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-PEO NEO [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonPeoNeoMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonPeoNeoMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonPeoNeoMember" xlink:to="lab_ecd_NonPeoNeoMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_019d1bac-cc86-7734-91ab-5e5bd72d861a_terseLabel_en-US" xlink:label="lab_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized and unrealized gain (loss)</link:label>
    <link:label id="lab_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax_label_en-US" xlink:label="lab_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax" xlink:to="lab_us-gaap_RealizedAndUnrealizedGainLossInvestmentDerivativeAndForeignCurrencyTransactionOperatingAfterTax" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockDividendRatePercentage_019e1496-4551-77ee-b30b-4d014b47b84a_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockDividendRatePercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Dividend rate</link:label>
    <link:label id="lab_us-gaap_PreferredStockDividendRatePercentage_label_en-US" xlink:label="lab_us-gaap_PreferredStockDividendRatePercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Dividend Rate, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockDividendRatePercentage" xlink:to="lab_us-gaap_PreferredStockDividendRatePercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestExpenseDebt_019d1bac-cbe9-7557-9006-ea0a8c41d53c_totalLabel_en-US" xlink:label="lab_us-gaap_InterestExpenseDebt" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total Interest Expense</link:label>
    <link:label id="lab_us-gaap_InterestExpenseDebt_label_en-US" xlink:label="lab_us-gaap_InterestExpenseDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Expense, Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestExpenseDebt" xlink:to="lab_us-gaap_InterestExpenseDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FeeIncome_019d1bac-cbe9-7f25-8739-a3adc95c4f2e_terseLabel_en-US" xlink:label="lab_us-gaap_FeeIncome" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fee income</link:label>
    <link:label id="lab_us-gaap_FeeIncome_label_en-US" xlink:label="lab_us-gaap_FeeIncome" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fee Income</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FeeIncome" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FeeIncome"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FeeIncome" xlink:to="lab_us-gaap_FeeIncome" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SeniorSecuredLoansFirstLienMember_019d1bac-cc86-7044-b22f-1ccc6134ae53_verboseLabel_en-US" xlink:label="lab_fsk_SeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans&#8212;First Lien</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansFirstLienMember_019d1bac-cc86-7e06-8a5d-edb82d8bbc63_terseLabel_en-US" xlink:label="lab_fsk_SeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Senior Secured Loans&#8212;First Lien</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansFirstLienMember_label_en-US" xlink:label="lab_fsk_SeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans, First Lien [Member]</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansFirstLienMember_documentation_en-US" xlink:label="lab_fsk_SeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans, First Lien</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SeniorSecuredLoansFirstLienMember" xlink:href="fsk-20260331.xsd#fsk_SeniorSecuredLoansFirstLienMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SeniorSecuredLoansFirstLienMember" xlink:to="lab_fsk_SeniorSecuredLoansFirstLienMember" xlink:type="arc" order="1"/>
    <link:label id="lab_currency_AllCurrenciesDomain_019d1bac-cc86-7586-97bf-8b414858c67d_terseLabel_en-US" xlink:label="lab_currency_AllCurrenciesDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Currencies [Domain]</link:label>
    <link:label id="lab_currency_AllCurrenciesDomain_label_en-US" xlink:label="lab_currency_AllCurrenciesDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Currencies [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_currency_AllCurrenciesDomain" xlink:to="lab_currency_AllCurrenciesDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OffsettingAssetsTableTextBlock_019d1bac-ccf8-729f-b795-6d0a2295a50c_terseLabel_en-US" xlink:label="lab_us-gaap_OffsettingAssetsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Offsetting Assets</link:label>
    <link:label id="lab_us-gaap_OffsettingAssetsTableTextBlock_label_en-US" xlink:label="lab_us-gaap_OffsettingAssetsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Offsetting Assets [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffsettingAssetsTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffsettingAssetsTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OffsettingAssetsTableTextBlock" xlink:to="lab_us-gaap_OffsettingAssetsTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrIndName_terseLabel_en-US" xlink:label="lab_ecd_TrdArrIndName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Name</link:label>
    <link:label id="lab_ecd_TrdArrIndName_label_en-US" xlink:label="lab_ecd_TrdArrIndName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement, Individual Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrIndName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrIndName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrIndName" xlink:to="lab_ecd_TrdArrIndName" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount_019d1bac-cc86-7b8d-9058-fcfa5235a09a_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded commitments</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount" xlink:to="lab_us-gaap_InvestmentCompanyFinancialCommitmentToInvesteeFutureAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Award Types</link:label>
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions_019d1bac-cc86-7215-afa9-e00e8c94b83b_totalLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Dividend Distribution, Percent Of Total Distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Dividend Distribution, Percent Of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:to="lab_fsk_InvestmentCompanyDividendDistributionPercentOfTotalDistributions" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CapitalGoodsSectorMember_019d1bac-cbe9-72fc-b210-e7ed3b2beb0b_terseLabel_en-US" xlink:label="lab_fsk_CapitalGoodsSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital Goods</link:label>
    <link:label id="lab_fsk_CapitalGoodsSectorMember_label_en-US" xlink:label="lab_fsk_CapitalGoodsSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Capital Goods Sector [Member]</link:label>
    <link:label id="lab_fsk_CapitalGoodsSectorMember_documentation_en-US" xlink:label="lab_fsk_CapitalGoodsSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Capital Goods Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CapitalGoodsSectorMember" xlink:href="fsk-20260331.xsd#fsk_CapitalGoodsSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CapitalGoodsSectorMember" xlink:to="lab_fsk_CapitalGoodsSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfShortTermDebtTable_019d1bac-cc86-7cbd-a349-d1e206dda728_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfShortTermDebtTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Short-Term Debt [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfShortTermDebtTable_label_en-US" xlink:label="lab_us-gaap_ScheduleOfShortTermDebtTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Short-Term Debt [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable" xlink:to="lab_us-gaap_ScheduleOfShortTermDebtTable" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_EqtyAwrdsAdjsMember_terseLabel_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments</link:label>
    <link:label id="lab_ecd_EqtyAwrdsAdjsMember_label_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_EqtyAwrdsAdjsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_EqtyAwrdsAdjsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_EqtyAwrdsAdjsMember" xlink:to="lab_ecd_EqtyAwrdsAdjsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PnsnBnftsAdjFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_PnsnBnftsAdjFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pension Benefits Adjustments, Footnote</link:label>
    <link:label id="lab_ecd_PnsnBnftsAdjFnTextBlock_label_en-US" xlink:label="lab_ecd_PnsnBnftsAdjFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pension Benefits Adjustments, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PnsnBnftsAdjFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PnsnBnftsAdjFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PnsnBnftsAdjFnTextBlock" xlink:to="lab_ecd_PnsnBnftsAdjFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FundedAssetBasedFinanceMember_019d1bac-ccf8-71d6-9b55-7ebe5c877a4a_terseLabel_en-US" xlink:label="lab_fsk_FundedAssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Funded - Asset Based Finance</link:label>
    <link:label id="lab_fsk_FundedAssetBasedFinanceMember_label_en-US" xlink:label="lab_fsk_FundedAssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Funded, Asset Based Finance [Member]</link:label>
    <link:label id="lab_fsk_FundedAssetBasedFinanceMember_documentation_en-US" xlink:label="lab_fsk_FundedAssetBasedFinanceMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Funded, Asset Based Finance</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FundedAssetBasedFinanceMember" xlink:href="fsk-20260331.xsd#fsk_FundedAssetBasedFinanceMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FundedAssetBasedFinanceMember" xlink:to="lab_fsk_FundedAssetBasedFinanceMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ValuationTechniqueOtherApproachMember_019d1bac-cc86-7928-9f04-009bbb559ad6_terseLabel_en-US" xlink:label="lab_fsk_ValuationTechniqueOtherApproachMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other</link:label>
    <link:label id="lab_fsk_ValuationTechniqueOtherApproachMember_label_en-US" xlink:label="lab_fsk_ValuationTechniqueOtherApproachMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation Technique, Other Approach [Member]</link:label>
    <link:label id="lab_fsk_ValuationTechniqueOtherApproachMember_documentation_en-US" xlink:label="lab_fsk_ValuationTechniqueOtherApproachMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Valuation Technique, Other Approach [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ValuationTechniqueOtherApproachMember" xlink:href="fsk-20260331.xsd#fsk_ValuationTechniqueOtherApproachMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ValuationTechniqueOtherApproachMember" xlink:to="lab_fsk_ValuationTechniqueOtherApproachMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_OutstandingRecoveryCompAmt_terseLabel_en-US" xlink:label="lab_ecd_OutstandingRecoveryCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation Amount</link:label>
    <link:label id="lab_ecd_OutstandingRecoveryCompAmt_label_en-US" xlink:label="lab_ecd_OutstandingRecoveryCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Recovery Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_OutstandingRecoveryCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_OutstandingRecoveryCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_OutstandingRecoveryCompAmt" xlink:to="lab_ecd_OutstandingRecoveryCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentFaceAmount_019d1bac-cc86-7c3d-a196-00e155925813_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentFaceAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Principal amount</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentFaceAmount_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentFaceAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Face Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentFaceAmount" xlink:to="lab_us-gaap_DebtInstrumentFaceAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember_019d6645-b3ba-7851-a93f-7bf71fa93a11_terseLabel_en-US" xlink:label="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized depreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember_label_en-US" xlink:label="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Depreciation On Foreign Currency Forward Contracts [Member]</link:label>
    <link:label id="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember_documentation_en-US" xlink:label="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unrealized Depreciation On Foreign Currency Forward Contracts</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:href="fsk-20260331.xsd#fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:to="lab_fsk_UnrealizedDepreciationOnForeignCurrencyForwardContractsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_019d1bac-cc86-7243-99b9-902e8eca2d94_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentNameDomain" xlink:to="lab_us-gaap_DebtInstrumentNameDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AustralianBankBillSwapBidRateMember_019d1bac-ccf8-773f-beaf-d5d39066aa51_terseLabel_en-US" xlink:label="lab_fsk_AustralianBankBillSwapBidRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">BBSY</link:label>
    <link:label id="lab_fsk_AustralianBankBillSwapBidRateMember_label_en-US" xlink:label="lab_fsk_AustralianBankBillSwapBidRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Australian Bank Bill Swap Bid Rate [Member]</link:label>
    <link:label id="lab_fsk_AustralianBankBillSwapBidRateMember_documentation_en-US" xlink:label="lab_fsk_AustralianBankBillSwapBidRateMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Australian Bank Bill Swap Bid Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AustralianBankBillSwapBidRateMember" xlink:href="fsk-20260331.xsd#fsk_AustralianBankBillSwapBidRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AustralianBankBillSwapBidRateMember" xlink:to="lab_fsk_AustralianBankBillSwapBidRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EquityOtherMember_019d1bac-cbe9-7022-b186-be1a601e09ec_terseLabel_en-US" xlink:label="lab_fsk_EquityOtherMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity/Other</link:label>
    <link:label id="lab_fsk_EquityOtherMember_label_en-US" xlink:label="lab_fsk_EquityOtherMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity/Other [Member]</link:label>
    <link:label id="lab_fsk_EquityOtherMember_documentation_en-US" xlink:label="lab_fsk_EquityOtherMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Equity/Other</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EquityOtherMember" xlink:href="fsk-20260331.xsd#fsk_EquityOtherMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EquityOtherMember" xlink:to="lab_fsk_EquityOtherMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_RecoveryOfErrCompDisclosureLineItems_label_en-US" xlink:label="lab_ecd_RecoveryOfErrCompDisclosureLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Recovery of Erroneously Awarded Compensation Disclosure [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_RecoveryOfErrCompDisclosureLineItems" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_RecoveryOfErrCompDisclosureLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_RecoveryOfErrCompDisclosureLineItems" xlink:to="lab_ecd_RecoveryOfErrCompDisclosureLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions_019d1bac-cc86-7b7f-ada0-a92e71522dd8_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Short-term capital gains proceeds from the sale of assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Short-Term Capital Gain, Percent of Total Distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Short-Term Capital Gain, Percent of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:to="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGainPercentOfTotalDistributions" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ShareRepurchaseProgramAxis_019d1bac-cc86-78f0-ac3b-1fe9dbebcb44_terseLabel_en-US" xlink:label="lab_srt_ShareRepurchaseProgramAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share Repurchase Program [Axis]</link:label>
    <link:label id="lab_srt_ShareRepurchaseProgramAxis_label_en-US" xlink:label="lab_srt_ShareRepurchaseProgramAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share Repurchase Program [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ShareRepurchaseProgramAxis" xlink:to="lab_srt_ShareRepurchaseProgramAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions_019d1bac-ccf8-7928-be5e-e0cd5da9cdec_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Structuring fee revenue</link:label>
    <link:label id="lab_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions_label_en-US" xlink:label="lab_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions" xlink:to="lab_us-gaap_InvestmentBankingAdvisoryBrokerageAndUnderwritingFeesAndCommissions" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfInvestmentsLineItems_019d1bac-cc86-730a-98e9-3600bd41d73b_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfInvestmentsLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Investments [Line Items]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfInvestmentsLineItems_label_en-US" xlink:label="lab_us-gaap_ScheduleOfInvestmentsLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Investments [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems" xlink:to="lab_us-gaap_ScheduleOfInvestmentsLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_MnpiDiscTimedForCompValFlag_terseLabel_en-US" xlink:label="lab_ecd_MnpiDiscTimedForCompValFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">MNPI Disclosure Timed for Compensation Value</link:label>
    <link:label id="lab_ecd_MnpiDiscTimedForCompValFlag_label_en-US" xlink:label="lab_ecd_MnpiDiscTimedForCompValFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">MNPI Disclosure Timed for Compensation Value [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_MnpiDiscTimedForCompValFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_MnpiDiscTimedForCompValFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_MnpiDiscTimedForCompValFlag" xlink:to="lab_ecd_MnpiDiscTimedForCompValFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentIssuerAffiliationDomain_019d1bac-cc86-7794-8de6-4e27c4a4d303_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentIssuerAffiliationDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment, Issuer Affiliation [Domain]</link:label>
    <link:label id="lab_us-gaap_InvestmentIssuerAffiliationDomain_label_en-US" xlink:label="lab_us-gaap_InvestmentIssuerAffiliationDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Issuer Affiliation [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIssuerAffiliationDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIssuerAffiliationDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="lab_us-gaap_InvestmentIssuerAffiliationDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscIndName_terseLabel_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscIndName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Name</link:label>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscIndName_label_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscIndName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards Close in Time to MNPI Disclosures, Individual Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardsCloseToMnpiDiscIndName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardsCloseToMnpiDiscIndName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardsCloseToMnpiDiscIndName" xlink:to="lab_ecd_AwardsCloseToMnpiDiscIndName" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent_019d1bac-cc86-7577-8db4-d38759674f46_terseLabel_en-US" xlink:label="lab_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other accrued expenses and liabilities</link:label>
    <link:label id="lab_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent_label_en-US" xlink:label="lab_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Accrued Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent" xlink:to="lab_us-gaap_OtherAccruedLiabilitiesCurrentAndNoncurrent" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract_019d1bac-cc86-72d0-ba14-f797cc85d512_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio/Supplemental Data:</link:label>
    <link:label id="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract_label_en-US" xlink:label="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Ratio To Average Net Assets And Supplemental Data [Abstract]</link:label>
    <link:label id="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Ratio To Average Net Assets And Supplemental Data</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:to="lab_fsk_InvestmentCompanyRatioToAverageNetAssetsAndSupplementalDataAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_LessThanGrossBorrowingBaseMember_019e0884-8be3-77fb-a4de-173abba7743f_terseLabel_en-US" xlink:label="lab_fsk_LessThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Less Than Gross Borrowing Base</link:label>
    <link:label id="lab_fsk_LessThanGrossBorrowingBaseMember_label_en-US" xlink:label="lab_fsk_LessThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Less Than Gross Borrowing Base [Member]</link:label>
    <link:label id="lab_fsk_LessThanGrossBorrowingBaseMember_documentation_en-US" xlink:label="lab_fsk_LessThanGrossBorrowingBaseMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Less Than Gross Borrowing Base</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_LessThanGrossBorrowingBaseMember" xlink:href="fsk-20260331.xsd#fsk_LessThanGrossBorrowingBaseMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_LessThanGrossBorrowingBaseMember" xlink:to="lab_fsk_LessThanGrossBorrowingBaseMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AggtErrCompNotYetDeterminedTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AggtErrCompNotYetDeterminedTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Erroneous Compensation Not Yet Determined</link:label>
    <link:label id="lab_ecd_AggtErrCompNotYetDeterminedTextBlock_label_en-US" xlink:label="lab_ecd_AggtErrCompNotYetDeterminedTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Erroneous Compensation Not Yet Determined [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AggtErrCompNotYetDeterminedTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AggtErrCompNotYetDeterminedTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AggtErrCompNotYetDeterminedTextBlock" xlink:to="lab_ecd_AggtErrCompNotYetDeterminedTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A7875UnsecuredNotesDue2029Member_019d1bac-cc86-790b-a4f1-4586be2e14e4_terseLabel_en-US" xlink:label="lab_fsk_A7875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">7.875% Notes due 2029</link:label>
    <link:label id="lab_fsk_A7875UnsecuredNotesDue2029Member_label_en-US" xlink:label="lab_fsk_A7875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">7.875% Unsecured Notes due 2029 [Member]</link:label>
    <link:label id="lab_fsk_A7875UnsecuredNotesDue2029Member_documentation_en-US" xlink:label="lab_fsk_A7875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">7.875% Unsecured Notes due 2029</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A7875UnsecuredNotesDue2029Member" xlink:href="fsk-20260331.xsd#fsk_A7875UnsecuredNotesDue2029Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A7875UnsecuredNotesDue2029Member" xlink:to="lab_fsk_A7875UnsecuredNotesDue2029Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RevenuesAbstract_019d1bac-cc86-7586-8c71-cb5048e44b9b_terseLabel_en-US" xlink:label="lab_us-gaap_RevenuesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment income</link:label>
    <link:label id="lab_us-gaap_RevenuesAbstract_label_en-US" xlink:label="lab_us-gaap_RevenuesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenues [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RevenuesAbstract" xlink:to="lab_us-gaap_RevenuesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod_019e14ac-85fb-7d25-9615-4bfbd3f346bc_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Issuer option, notification period</link:label>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod_label_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Issuer Option, Required Redemption For Cash, Notice Period</link:label>
    <link:label id="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod_documentation_en-US" xlink:label="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Issuer Option, Required Redemption For Cash, Notice Period</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:href="fsk-20260331.xsd#fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:to="lab_fsk_PreferredStockIssuerOptionRequiredRedemptionForCashNoticePeriod" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A190TermLoanOutstandingMember_019d1bac-cbe9-70ae-900b-448747f1043f_terseLabel_en-US" xlink:label="lab_fsk_A190TermLoanOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.90% Term Loan Outstanding</link:label>
    <link:label id="lab_fsk_A190TermLoanOutstandingMember_label_en-US" xlink:label="lab_fsk_A190TermLoanOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.90% Term Loan Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A190TermLoanOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A190TermLoanOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.90% Term Loan Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A190TermLoanOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A190TermLoanOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A190TermLoanOutstandingMember" xlink:to="lab_fsk_A190TermLoanOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EuroInterbankOfferRateEURIBORMember_019d1bac-cbe9-71ab-971b-96f227fd6acf_terseLabel_en-US" xlink:label="lab_fsk_EuroInterbankOfferRateEURIBORMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Euro Interbank Offer Rate (EURIBOR)</link:label>
    <link:label id="lab_fsk_EuroInterbankOfferRateEURIBORMember_label_en-US" xlink:label="lab_fsk_EuroInterbankOfferRateEURIBORMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Euro Interbank Offer Rate (EURIBOR) [Member]</link:label>
    <link:label id="lab_fsk_EuroInterbankOfferRateEURIBORMember_documentation_en-US" xlink:label="lab_fsk_EuroInterbankOfferRateEURIBORMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Euro Interbank Offer Rate (EURIBOR)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EuroInterbankOfferRateEURIBORMember" xlink:href="fsk-20260331.xsd#fsk_EuroInterbankOfferRateEURIBORMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EuroInterbankOfferRateEURIBORMember" xlink:to="lab_fsk_EuroInterbankOfferRateEURIBORMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019daace-108a-72f9-b62f-862115560292_terseLabel_en-US" xlink:label="lab_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Instruments [Domain]</link:label>
    <link:label id="lab_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_label_en-US" xlink:label="lab_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Instruments [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="lab_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019d1bac-cc86-7780-a96c-37f99001c256_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Purchases</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:to="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncomeStatementLocationAxis_019d1bac-cc86-70f7-b667-353eeb2413cf_terseLabel_en-US" xlink:label="lab_us-gaap_IncomeStatementLocationAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income Statement Location [Axis]</link:label>
    <link:label id="lab_us-gaap_IncomeStatementLocationAxis_label_en-US" xlink:label="lab_us-gaap_IncomeStatementLocationAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Income Location, Balance [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncomeStatementLocationAxis" xlink:to="lab_us-gaap_IncomeStatementLocationAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019d1bac-cbe9-7d50-98ef-0455df400377_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amount Available</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Remaining Borrowing Capacity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:to="lab_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AggtPnsnAdjsSvcCstMember_terseLabel_en-US" xlink:label="lab_ecd_AggtPnsnAdjsSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Pension Adjustments Service Cost</link:label>
    <link:label id="lab_ecd_AggtPnsnAdjsSvcCstMember_label_en-US" xlink:label="lab_ecd_AggtPnsnAdjsSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Pension Adjustments Service Cost [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AggtPnsnAdjsSvcCstMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AggtPnsnAdjsSvcCstMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AggtPnsnAdjsSvcCstMember" xlink:to="lab_ecd_AggtPnsnAdjsSvcCstMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d1bac-cc86-7846-b96d-445aa8794893_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DeferredTaxLiabilitiesInvestments_019e007c-8c0d-7571-be35-566076b16a60_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredTaxLiabilitiesInvestments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred tax liabilities</link:label>
    <link:label id="lab_us-gaap_DeferredTaxLiabilitiesInvestments_label_en-US" xlink:label="lab_us-gaap_DeferredTaxLiabilitiesInvestments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Tax Liabilities, Investments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesInvestments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilitiesInvestments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DeferredTaxLiabilitiesInvestments" xlink:to="lab_us-gaap_DeferredTaxLiabilitiesInvestments" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_BalanceSheetLocationDomain_019d6645-3238-7149-8709-e09d852d7fe9_terseLabel_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statement of Financial Position Location, Balance [Domain]</link:label>
    <link:label id="lab_us-gaap_BalanceSheetLocationDomain_label_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position Location, Balance [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_BalanceSheetLocationDomain" xlink:to="lab_us-gaap_BalanceSheetLocationDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019d1bac-cbe9-76b2-a876-50dd9e672629_terseLabel_en-US" xlink:label="lab_us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amortization of deferred financing costs and discount</link:label>
    <link:label id="lab_us-gaap_AmortizationOfFinancingCostsAndDiscounts_label_en-US" xlink:label="lab_us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amortization of Debt Issuance Costs and Discounts</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:to="lab_us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_MinimumMember_019d1bac-cc86-73fb-88a7-7ee12fe16cc1_terseLabel_en-US" xlink:label="lab_srt_MinimumMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Minimum</link:label>
    <link:label id="lab_srt_MinimumMember_label_en-US" xlink:label="lab_srt_MinimumMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Minimum [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_MinimumMember" xlink:to="lab_srt_MinimumMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeAssetsAbstract_019d1bac-cc86-74a5-8d23-ad170ddeb042_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeAssetsAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Asset [Abstract]</link:label>
    <link:label id="lab_us-gaap_DerivativeAssetsAbstract_label_en-US" xlink:label="lab_us-gaap_DerivativeAssetsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeAssetsAbstract" xlink:to="lab_us-gaap_DerivativeAssetsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeCollateralObligationToReturnCash_019d1bac-cc86-70c0-a2d1-39180b066a01_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DerivativeCollateralObligationToReturnCash" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Cash Collateral Received</link:label>
    <link:label id="lab_us-gaap_DerivativeCollateralObligationToReturnCash_label_en-US" xlink:label="lab_us-gaap_DerivativeCollateralObligationToReturnCash" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCollateralObligationToReturnCash" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeCollateralObligationToReturnCash"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeCollateralObligationToReturnCash" xlink:to="lab_us-gaap_DerivativeCollateralObligationToReturnCash" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CoSelectedMeasureName_terseLabel_en-US" xlink:label="lab_ecd_CoSelectedMeasureName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Company Selected Measure Name</link:label>
    <link:label id="lab_ecd_CoSelectedMeasureName_label_en-US" xlink:label="lab_ecd_CoSelectedMeasureName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Company Selected Measure Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CoSelectedMeasureName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CoSelectedMeasureName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CoSelectedMeasureName" xlink:to="lab_ecd_CoSelectedMeasureName" xlink:type="arc" order="1"/>
    <link:label id="lab_currency_AUD_019d1bac-cbe9-7aa1-9506-4c9158555004_terseLabel_en-US" xlink:label="lab_currency_AUD" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">AUD</link:label>
    <link:label id="lab_currency_AUD_label_en-US" xlink:label="lab_currency_AUD" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Australia, Dollars</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AUD" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AUD"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_currency_AUD" xlink:to="lab_currency_AUD" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee_019e14be-89ca-7486-ae4e-d6a629006daf_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Incentive fee waived, percent of the subordinated incentive fee that would otherwise be paid by the company</link:label>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee_label_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Incentive Fee Waived, Percent Of Applicable Incentive Fee</link:label>
    <link:label id="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Incentive Fee Waived, Percent Of Applicable Incentive Fee</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:to="lab_fsk_InvestmentCompanyIncentiveFeeWaivedPercentOfApplicableIncentiveFee" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SeniorNotesMember_019d1bac-ccf8-7dc2-a6e7-4c03b0e83f53_terseLabel_en-US" xlink:label="lab_us-gaap_SeniorNotesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Senior Notes</link:label>
    <link:label id="lab_us-gaap_SeniorNotesMember_label_en-US" xlink:label="lab_us-gaap_SeniorNotesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior Notes [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SeniorNotesMember" xlink:to="lab_us-gaap_SeniorNotesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeLiabilityFairValueGrossAsset_019d1bac-cbe9-7223-a5c3-1d45c7aa2f40_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeLiabilityFairValueGrossAsset" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivatives Available for Offset</link:label>
    <link:label id="lab_us-gaap_DerivativeLiabilityFairValueGrossAsset_label_en-US" xlink:label="lab_us-gaap_DerivativeLiabilityFairValueGrossAsset" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability, Subject to Master Netting Arrangement, Asset Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset" xlink:to="lab_us-gaap_DerivativeLiabilityFairValueGrossAsset" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtDisclosureTextBlock_019d1bac-cc86-70ba-91e3-63b49f41597f_terseLabel_en-US" xlink:label="lab_us-gaap_DebtDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financing Arrangements</link:label>
    <link:label id="lab_us-gaap_DebtDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_DebtDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtDisclosureTextBlock" xlink:to="lab_us-gaap_DebtDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockValue_019d1bac-cc86-7691-b26d-d47655ca6b39_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, $0.001 par value, 50,000,000 shares authorized, none issued and outstanding</link:label>
    <link:label id="lab_us-gaap_PreferredStockValue_label_en-US" xlink:label="lab_us-gaap_PreferredStockValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Value, Issued</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockValue" xlink:to="lab_us-gaap_PreferredStockValue" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrSecuritiesAggAvailAmt_terseLabel_en-US" xlink:label="lab_ecd_TrdArrSecuritiesAggAvailAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Available</link:label>
    <link:label id="lab_ecd_TrdArrSecuritiesAggAvailAmt_label_en-US" xlink:label="lab_ecd_TrdArrSecuritiesAggAvailAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement, Securities Aggregate Available Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrSecuritiesAggAvailAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrSecuritiesAggAvailAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrSecuritiesAggAvailAmt" xlink:to="lab_ecd_TrdArrSecuritiesAggAvailAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyPortfolioTurnover_019d1bac-cc86-79cc-9647-4af1fd83c25b_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyPortfolioTurnover" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Portfolio turnover</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyPortfolioTurnover_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyPortfolioTurnover" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Portfolio Turnover</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyPortfolioTurnover" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyPortfolioTurnover"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyPortfolioTurnover" xlink:to="lab_us-gaap_InvestmentCompanyPortfolioTurnover" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AdministrativeFeeExpenseBrokenDealCost_019d1bac-cc86-7eba-966a-4fd3821586c3_terseLabel_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Broken deal cost</link:label>
    <link:label id="lab_fsk_AdministrativeFeeExpenseBrokenDealCost_label_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Administrative Fee Expense, Broken Deal Cost</link:label>
    <link:label id="lab_fsk_AdministrativeFeeExpenseBrokenDealCost_documentation_en-US" xlink:label="lab_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Administrative Fee Expense, Broken Deal Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:href="fsk-20260331.xsd#fsk_AdministrativeFeeExpenseBrokenDealCost"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:to="lab_fsk_AdministrativeFeeExpenseBrokenDealCost" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestPayableCurrentAndNoncurrent_019d1bac-cc86-7000-8cda-0d9b7e8a3ee8_terseLabel_en-US" xlink:label="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest payable</link:label>
    <link:label id="lab_us-gaap_InterestPayableCurrentAndNoncurrent_label_en-US" xlink:label="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:to="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockAppreciationRightsSARSMember_terseLabel_en-US" xlink:label="lab_us-gaap_StockAppreciationRightsSARSMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Appreciation Rights (SARs)</link:label>
    <link:label id="lab_us-gaap_StockAppreciationRightsSARSMember_label_en-US" xlink:label="lab_us-gaap_StockAppreciationRightsSARSMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Appreciation Rights (SARs) [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockAppreciationRightsSARSMember" xlink:to="lab_us-gaap_StockAppreciationRightsSARSMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_019d1bac-cc86-728f-9055-e8ebb2ece529_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from sales and repayments of investments</link:label>
    <link:label id="lab_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity_label_en-US" xlink:label="lab_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from Disposition of Investment, Operating Activity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity" xlink:to="lab_us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashHeldInForeignCurrencyAcquisitionCost_019d1bac-cbe9-7cbc-bcab-1f011f76c97f_terseLabel_en-US" xlink:label="lab_us-gaap_CashHeldInForeignCurrencyAcquisitionCost" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Foreign currency, cost</link:label>
    <link:label id="lab_us-gaap_CashHeldInForeignCurrencyAcquisitionCost_label_en-US" xlink:label="lab_us-gaap_CashHeldInForeignCurrencyAcquisitionCost" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalent, Held in Foreign Currency, Acquisition Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashHeldInForeignCurrencyAcquisitionCost" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashHeldInForeignCurrencyAcquisitionCost"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashHeldInForeignCurrencyAcquisitionCost" xlink:to="lab_us-gaap_CashHeldInForeignCurrencyAcquisitionCost" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubordinatedDebtMember_019d1bac-ccf8-721e-87c1-429755ff795f_terseLabel_en-US" xlink:label="lab_us-gaap_SubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subordinated Debt</link:label>
    <link:label id="lab_us-gaap_SubordinatedDebtMember_019d1bac-ccf8-7936-8016-0d20ee338f3b_verboseLabel_en-US" xlink:label="lab_us-gaap_SubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Subordinated Debt</link:label>
    <link:label id="lab_us-gaap_SubordinatedDebtMember_label_en-US" xlink:label="lab_us-gaap_SubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subordinated Debt [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebtMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubordinatedDebtMember" xlink:to="lab_us-gaap_SubordinatedDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AllExecutiveCategoriesMember_terseLabel_en-US" xlink:label="lab_ecd_AllExecutiveCategoriesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Executive Categories</link:label>
    <link:label id="lab_ecd_AllExecutiveCategoriesMember_label_en-US" xlink:label="lab_ecd_AllExecutiveCategoriesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Executive Categories [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllExecutiveCategoriesMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllExecutiveCategoriesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AllExecutiveCategoriesMember" xlink:to="lab_ecd_AllExecutiveCategoriesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_NetStockIssuedRepurchaseValue_019d1bac-cc86-78f9-b3a6-6fb5a646edda_totalLabel_en-US" xlink:label="lab_fsk_NetStockIssuedRepurchaseValue" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net Proceeds from Share Transactions</link:label>
    <link:label id="lab_fsk_NetStockIssuedRepurchaseValue_label_en-US" xlink:label="lab_fsk_NetStockIssuedRepurchaseValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Stock Issued (Repurchase), Value</link:label>
    <link:label id="lab_fsk_NetStockIssuedRepurchaseValue_documentation_en-US" xlink:label="lab_fsk_NetStockIssuedRepurchaseValue" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Net Stock Issued (Repurchase), Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_NetStockIssuedRepurchaseValue" xlink:href="fsk-20260331.xsd#fsk_NetStockIssuedRepurchaseValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_NetStockIssuedRepurchaseValue" xlink:to="lab_fsk_NetStockIssuedRepurchaseValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockValue_019d1bac-cc86-74d2-87cf-7c85daf9f931_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common stock, $0.001 par value, 750,000,000 shares authorized, 280,066,433 and 280,066,433 shares issued and outstanding, respectively</link:label>
    <link:label id="lab_us-gaap_CommonStockValue_label_en-US" xlink:label="lab_us-gaap_CommonStockValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Value, Issued</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockValue" xlink:to="lab_us-gaap_CommonStockValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentForAdministrativeFees_019d1bac-ccf8-7318-8909-ef0d271a0c10_terseLabel_en-US" xlink:label="lab_us-gaap_PaymentForAdministrativeFees" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Payment for administrative services expenses</link:label>
    <link:label id="lab_us-gaap_PaymentForAdministrativeFees_label_en-US" xlink:label="lab_us-gaap_PaymentForAdministrativeFees" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payment for Administrative Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForAdministrativeFees" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentForAdministrativeFees"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentForAdministrativeFees" xlink:to="lab_us-gaap_PaymentForAdministrativeFees" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_019d1bac-cbe9-7cf8-9250-bdf5f9d0a486_terseLabel_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies</link:label>
    <link:label id="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019d1bac-cc86-7381-8f63-8d989c718969_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DerivativeAssetAverageNotionalBalance_019d1bac-cc86-7315-b521-89653f4070b1_terseLabel_en-US" xlink:label="lab_fsk_DerivativeAssetAverageNotionalBalance" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average notional balance</link:label>
    <link:label id="lab_fsk_DerivativeAssetAverageNotionalBalance_label_en-US" xlink:label="lab_fsk_DerivativeAssetAverageNotionalBalance" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Average Notional Balance</link:label>
    <link:label id="lab_fsk_DerivativeAssetAverageNotionalBalance_documentation_en-US" xlink:label="lab_fsk_DerivativeAssetAverageNotionalBalance" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Derivative Asset, Average Notional Balance</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DerivativeAssetAverageNotionalBalance" xlink:href="fsk-20260331.xsd#fsk_DerivativeAssetAverageNotionalBalance"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DerivativeAssetAverageNotionalBalance" xlink:to="lab_fsk_DerivativeAssetAverageNotionalBalance" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019d1bac-cc86-7e1a-a33f-e3a3f5f8f8cd_terseLabel_en-US" xlink:label="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted average shares outstanding - diluted (in shares)</link:label>
    <link:label id="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_label_en-US" xlink:label="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted Average Number of Shares Outstanding, Diluted</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SegmentReportingPolicyPolicyTextBlock_019d1bac-cc86-7dc7-a851-cdebb3eb93dc_terseLabel_en-US" xlink:label="lab_us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Segment Reporting</link:label>
    <link:label id="lab_us-gaap_SegmentReportingPolicyPolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Segment Reporting, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingPolicyPolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:to="lab_us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommitmentsAndContingencies_019d1bac-cc86-7675-86d6-fe7b583e208f_terseLabel_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingencies" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Commitments and contingencies</link:label>
    <link:label id="lab_us-gaap_CommitmentsAndContingencies_label_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingencies" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommitmentsAndContingencies" xlink:to="lab_us-gaap_CommitmentsAndContingencies" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities_019d1bac-cc86-70d5-a929-1fd077c85858_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-cash Collateral Pledged</link:label>
    <link:label id="lab_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities_label_en-US" xlink:label="lab_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Security Not Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities" xlink:to="lab_us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedCollateralRightToReclaimSecurities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis_019d1bac-cc86-7c67-8e67-0988540c17b7_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Support to Nonconsolidated Legal Entity [Axis]</link:label>
    <link:label id="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis_label_en-US" xlink:label="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Support to Nonconsolidated Legal Entity [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis" xlink:to="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction_019d1bac-cc86-7aea-95be-ef1196bd32b9_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from capital share transactions</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Capital Share Transaction, Increase (Decrease)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction" xlink:to="lab_us-gaap_InvestmentCompanyIncreaseDecreaseFromShareTransaction" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonGaapMeasureDescriptionTextBlock_terseLabel_en-US" xlink:label="lab_ecd_NonGaapMeasureDescriptionTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-GAAP Measure Description</link:label>
    <link:label id="lab_ecd_NonGaapMeasureDescriptionTextBlock_label_en-US" xlink:label="lab_ecd_NonGaapMeasureDescriptionTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-GAAP Measure Description [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonGaapMeasureDescriptionTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonGaapMeasureDescriptionTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonGaapMeasureDescriptionTextBlock" xlink:to="lab_ecd_NonGaapMeasureDescriptionTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember_019d1bac-cc86-7105-b9fb-cd545fd44f49_terseLabel_en-US" xlink:label="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consumer Discretionary Distribution &amp; Retail</link:label>
    <link:label id="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember_label_en-US" xlink:label="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consumer Discretionary Distribution &amp; Retail Sector [Member]</link:label>
    <link:label id="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember_documentation_en-US" xlink:label="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Consumer Discretionary Distribution &amp; Retail Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:href="fsk-20260331.xsd#fsk_ConsumerDiscretionaryDistributionRetailSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:to="lab_fsk_ConsumerDiscretionaryDistributionRetailSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio_019d1bac-cc86-7495-842a-b90eb467d675_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Asset coverage per ratio (as percent)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio_019d1bac-cc86-7c18-883a-e4738893286c_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Asset coverage per unit</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Senior Security, Indebtedness, Asset Coverage Ratio</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:to="lab_us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeTable_019d1bac-cc86-7a88-9400-5bd5eed21af0_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative [Table]</link:label>
    <link:label id="lab_us-gaap_DerivativeTable_label_en-US" xlink:label="lab_us-gaap_DerivativeTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeTable" xlink:to="lab_us-gaap_DerivativeTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_019d1bac-cc86-7ea0-ac33-dda3d7eea760_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments measured at net asset value</link:label>
    <link:label id="lab_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_label_en-US" xlink:label="lab_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Measured at Net Asset Value Per Share [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:to="lab_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntitySmallBusiness_019d1bac-cc86-799c-852e-3b1a5ab7754e_terseLabel_en-US" xlink:label="lab_dei_EntitySmallBusiness" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Small Business</link:label>
    <link:label id="lab_dei_EntitySmallBusiness_label_en-US" xlink:label="lab_dei_EntitySmallBusiness" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Small Business</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntitySmallBusiness" xlink:to="lab_dei_EntitySmallBusiness" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_NetSubordinatedDebtMember_019d1bac-cc86-7b66-a024-d68deb151000_terseLabel_en-US" xlink:label="lab_fsk_NetSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net Subordinated Debt</link:label>
    <link:label id="lab_fsk_NetSubordinatedDebtMember_label_en-US" xlink:label="lab_fsk_NetSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Subordinated Debt [Member]</link:label>
    <link:label id="lab_fsk_NetSubordinatedDebtMember_documentation_en-US" xlink:label="lab_fsk_NetSubordinatedDebtMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Net Subordinated Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_NetSubordinatedDebtMember" xlink:href="fsk-20260331.xsd#fsk_NetSubordinatedDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_NetSubordinatedDebtMember" xlink:to="lab_fsk_NetSubordinatedDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockConvertibleConversionPrice_019e1499-2613-778d-bec6-f04f5d5c43ed_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockConvertibleConversionPrice" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Conversion price (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_PreferredStockConvertibleConversionPrice_label_en-US" xlink:label="lab_us-gaap_PreferredStockConvertibleConversionPrice" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Conversion Price</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockConvertibleConversionPrice" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockConvertibleConversionPrice"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockConvertibleConversionPrice" xlink:to="lab_us-gaap_PreferredStockConvertibleConversionPrice" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2030Member_019d1bac-ccf8-7cdf-b7c6-0a9b4f74d99a_terseLabel_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2030Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">6.125% Notes due 2030</link:label>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2030Member_label_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2030Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">6.125% Unsecured Notes due 2030 [Member]</link:label>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2030Member_documentation_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2030Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">6.125% Unsecured Notes due 2030</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A6.125UnsecuredNotesDue2030Member" xlink:href="fsk-20260331.xsd#fsk_A6.125UnsecuredNotesDue2030Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A6.125UnsecuredNotesDue2030Member" xlink:to="lab_fsk_A6.125UnsecuredNotesDue2030Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput_019d1bac-cc86-7121-9ee7-f7458a08bb9e_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Measurement input</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Investment Owned, Measurement Input</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput" xlink:to="lab_us-gaap_InvestmentCompanyInvestmentOwnedFairValueMeasurementInput" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockSharesOutstanding_019d1bac-ccf8-7486-9773-8af90ee71301_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, shares outstanding (in shares)</link:label>
    <link:label id="lab_us-gaap_PreferredStockSharesOutstanding_label_en-US" xlink:label="lab_us-gaap_PreferredStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Shares Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockSharesOutstanding" xlink:to="lab_us-gaap_PreferredStockSharesOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DistributionPayable_019d1bac-cc86-7a34-9515-63d6c983ff0f_terseLabel_en-US" xlink:label="lab_us-gaap_DistributionPayable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stockholder distributions payable</link:label>
    <link:label id="lab_us-gaap_DistributionPayable_label_en-US" xlink:label="lab_us-gaap_DistributionPayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Distribution Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionPayable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DistributionPayable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DistributionPayable" xlink:to="lab_us-gaap_DistributionPayable" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentTransitionReport_019d1bac-cc86-7236-bdd6-6b4aca053896_terseLabel_en-US" xlink:label="lab_dei_DocumentTransitionReport" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Transition Report</link:label>
    <link:label id="lab_dei_DocumentTransitionReport_label_en-US" xlink:label="lab_dei_DocumentTransitionReport" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Transition Report</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentTransitionReport" xlink:to="lab_dei_DocumentTransitionReport" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardUndrlygSecuritiesAmt_terseLabel_en-US" xlink:label="lab_ecd_AwardUndrlygSecuritiesAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Underlying Securities</link:label>
    <link:label id="lab_ecd_AwardUndrlygSecuritiesAmt_label_en-US" xlink:label="lab_ecd_AwardUndrlygSecuritiesAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Underlying Securities Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardUndrlygSecuritiesAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardUndrlygSecuritiesAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardUndrlygSecuritiesAmt" xlink:to="lab_ecd_AwardUndrlygSecuritiesAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ShortTermDebtLineItems_019d1bac-cc86-79e5-a85b-daa9e8b6b8c3_terseLabel_en-US" xlink:label="lab_us-gaap_ShortTermDebtLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Short-Term Debt [Line Items]</link:label>
    <link:label id="lab_us-gaap_ShortTermDebtLineItems_label_en-US" xlink:label="lab_us-gaap_ShortTermDebtLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Short-Term Debt [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShortTermDebtLineItems" xlink:to="lab_us-gaap_ShortTermDebtLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger_019d1bac-cbe9-7d44-9fe4-e79e1495544a_negatedTerseLabel_en-US" xlink:label="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized (appreciation) depreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger_label_en-US" xlink:label="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Gain (Loss) on Derivatives Including Effects From Merger</link:label>
    <link:label id="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger_documentation_en-US" xlink:label="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unrealized Gain (Loss) on Derivatives Including Effects From Merger</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:href="fsk-20260331.xsd#fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:to="lab_fsk_UnrealizedGainLossOnDerivativesIncludingEffectsFromMerger" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration_019d1bac-cbe9-76d7-962d-c1bb0809c5f2_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Credit opportunities partners JV, LLC, entitled to a fee percentage</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration_label_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Percentage Of Fee Entitled On Assets Under Administration</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Percentage Of Fee Entitled On Assets Under Administration</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:to="lab_fsk_InvestmentCompanyCommittedCapitalPercentageOfFeeEntitledOnAssetsUnderAdministration" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AffiliatedPurchaserProgramMember_019d1bac-cc86-76bd-8676-91720bb2e984_terseLabel_en-US" xlink:label="lab_fsk_AffiliatedPurchaserProgramMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Affiliated Purchaser Program</link:label>
    <link:label id="lab_fsk_AffiliatedPurchaserProgramMember_label_en-US" xlink:label="lab_fsk_AffiliatedPurchaserProgramMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Affiliated Purchaser Program [Member]</link:label>
    <link:label id="lab_fsk_AffiliatedPurchaserProgramMember_documentation_en-US" xlink:label="lab_fsk_AffiliatedPurchaserProgramMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Affiliated Purchaser Program</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AffiliatedPurchaserProgramMember" xlink:href="fsk-20260331.xsd#fsk_AffiliatedPurchaserProgramMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AffiliatedPurchaserProgramMember" xlink:to="lab_fsk_AffiliatedPurchaserProgramMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock_019d1bac-cbe9-7d2c-b1b2-f7ad28b089ce_terseLabel_en-US" xlink:label="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of the Fees and Expenses Accrued</link:label>
    <link:label id="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock_label_en-US" xlink:label="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule Of Investment Advisory Agreement [Table Text Block]</link:label>
    <link:label id="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock_documentation_en-US" xlink:label="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule Of Investment Advisory Agreement</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:href="fsk-20260331.xsd#fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:to="lab_fsk_ScheduleOfInvestmentAdvisoryAgreementTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentPeriodEndDate_019d1bac-cbe9-75cc-b577-7fed750f9a92_terseLabel_en-US" xlink:label="lab_dei_DocumentPeriodEndDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Period End Date</link:label>
    <link:label id="lab_dei_DocumentPeriodEndDate_label_en-US" xlink:label="lab_dei_DocumentPeriodEndDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Period End Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentPeriodEndDate" xlink:to="lab_dei_DocumentPeriodEndDate" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeoActuallyPaidCompAmt_terseLabel_en-US" xlink:label="lab_ecd_PeoActuallyPaidCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">PEO Actually Paid Compensation Amount</link:label>
    <link:label id="lab_ecd_PeoActuallyPaidCompAmt_label_en-US" xlink:label="lab_ecd_PeoActuallyPaidCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">PEO Actually Paid Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeoActuallyPaidCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeoActuallyPaidCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeoActuallyPaidCompAmt" xlink:to="lab_ecd_PeoActuallyPaidCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_TermLoanOutstanding_019d1bac-cc86-70cc-a169-3542ae6cbff4_terseLabel_en-US" xlink:label="lab_fsk_TermLoanOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Term loan outstanding</link:label>
    <link:label id="lab_fsk_TermLoanOutstanding_label_en-US" xlink:label="lab_fsk_TermLoanOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Term Loan Outstanding</link:label>
    <link:label id="lab_fsk_TermLoanOutstanding_documentation_en-US" xlink:label="lab_fsk_TermLoanOutstanding" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Term Loan Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_TermLoanOutstanding" xlink:href="fsk-20260331.xsd#fsk_TermLoanOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_TermLoanOutstanding" xlink:to="lab_fsk_TermLoanOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019dfefd-24af-788e-a671-2227d7b3b6e2_terseLabel_en-US" xlink:label="lab_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents [Domain]</link:label>
    <link:label id="lab_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_label_en-US" xlink:label="lab_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:to="lab_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A8625UnsecuredNotesDue2025Member_019d1bac-cc86-7235-805a-3aa7848d8d99_terseLabel_en-US" xlink:label="lab_fsk_A8625UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">8.625% Notes due 2025</link:label>
    <link:label id="lab_fsk_A8625UnsecuredNotesDue2025Member_label_en-US" xlink:label="lab_fsk_A8625UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">8.625% Unsecured Notes due 2025 [Member]</link:label>
    <link:label id="lab_fsk_A8625UnsecuredNotesDue2025Member_documentation_en-US" xlink:label="lab_fsk_A8625UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">8.625% Unsecured Notes due 2025</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A8625UnsecuredNotesDue2025Member" xlink:href="fsk-20260331.xsd#fsk_A8625UnsecuredNotesDue2025Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A8625UnsecuredNotesDue2025Member" xlink:to="lab_fsk_A8625UnsecuredNotesDue2025Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ScheduleOfDistributionTable_019d1bac-cc86-736d-bdf7-d35dcd9d502d_terseLabel_en-US" xlink:label="lab_fsk_ScheduleOfDistributionTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Distributions [Table]</link:label>
    <link:label id="lab_fsk_ScheduleOfDistributionTable_label_en-US" xlink:label="lab_fsk_ScheduleOfDistributionTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Distribution [Table]</link:label>
    <link:label id="lab_fsk_ScheduleOfDistributionTable_documentation_en-US" xlink:label="lab_fsk_ScheduleOfDistributionTable" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule of Distribution [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ScheduleOfDistributionTable" xlink:href="fsk-20260331.xsd#fsk_ScheduleOfDistributionTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ScheduleOfDistributionTable" xlink:to="lab_fsk_ScheduleOfDistributionTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnfundedAssetBasedFinanceNettingMember_019d1bac-cc86-7475-897e-5b9260a5ac75_terseLabel_en-US" xlink:label="lab_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded, Asset Based Finance, Netting</link:label>
    <link:label id="lab_fsk_UnfundedAssetBasedFinanceNettingMember_label_en-US" xlink:label="lab_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unfunded, Asset Based Finance, Netting [Member]</link:label>
    <link:label id="lab_fsk_UnfundedAssetBasedFinanceNettingMember_documentation_en-US" xlink:label="lab_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unfunded, Asset Based Finance, Netting</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:href="fsk-20260331.xsd#fsk_UnfundedAssetBasedFinanceNettingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:to="lab_fsk_UnfundedAssetBasedFinanceNettingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscTableTextBlock_terseLabel_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Awards Close in Time to MNPI Disclosures, Table</link:label>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscTableTextBlock_label_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards Close in Time to MNPI Disclosures [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardsCloseToMnpiDiscTableTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardsCloseToMnpiDiscTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardsCloseToMnpiDiscTableTextBlock" xlink:to="lab_ecd_AwardsCloseToMnpiDiscTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare_019e1493-d0e0-7e8e-a396-c65bd43f6b13_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percent of liquidation preference per share payable in cash</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare_label_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable, Cash, Percent Of Liquidation Preference Per Share</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare_documentation_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable, Cash, Percent Of Liquidation Preference Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:href="fsk-20260331.xsd#fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:to="lab_fsk_PreferredStockDiviendPayableCashPercentOfLiquidationPreferencePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfInvestmentsTable_019d1bac-cc86-7186-a7af-9aae3500d496_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfInvestmentsTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Investments [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfInvestmentsTable_label_en-US" xlink:label="lab_us-gaap_ScheduleOfInvestmentsTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Investments [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable" xlink:to="lab_us-gaap_ScheduleOfInvestmentsTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio_019d1bac-cc86-7c5f-a578-6867f1609373_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Contributed capital to committed capital ratio</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Contributed Capital to Committed Capital Ratio</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio" xlink:to="lab_us-gaap_InvestmentCompanyContributedCapitalToCommittedCapitalRatio" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DistributionReinvestmentPlanMember_019d1bac-cc86-7bc4-8c23-fae37c0eb202_terseLabel_en-US" xlink:label="lab_fsk_DistributionReinvestmentPlanMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Distribution Reinvestment Plan</link:label>
    <link:label id="lab_fsk_DistributionReinvestmentPlanMember_label_en-US" xlink:label="lab_fsk_DistributionReinvestmentPlanMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Distribution Reinvestment Plan [Member]</link:label>
    <link:label id="lab_fsk_DistributionReinvestmentPlanMember_documentation_en-US" xlink:label="lab_fsk_DistributionReinvestmentPlanMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Distribution Reinvestment Plan</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DistributionReinvestmentPlanMember" xlink:href="fsk-20260331.xsd#fsk_DistributionReinvestmentPlanMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DistributionReinvestmentPlanMember" xlink:to="lab_fsk_DistributionReinvestmentPlanMember" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_StatementScenarioAxis_019e14c2-af5b-7e8d-b900-77ec1305ac95_terseLabel_en-US" xlink:label="lab_srt_StatementScenarioAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Scenario [Axis]</link:label>
    <link:label id="lab_srt_StatementScenarioAxis_label_en-US" xlink:label="lab_srt_StatementScenarioAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_StatementScenarioAxis" xlink:to="lab_srt_StatementScenarioAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_019d1bac-ccf8-7c57-a133-bef3755ea753_totalLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net Amount of Derivative Assets</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_label_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Including Not Subject to Master Netting Arrangement, after Offset and Deduction</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral" xlink:to="lab_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements_019d1bac-cc86-7261-b26f-4fd2b4d7c7e4_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio of net operating expenses to average net assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements_label_en-US" xlink:label="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Expense Ratio Including Fee Waiver And Reimbursements</link:label>
    <link:label id="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Expense Ratio Including Fee Waiver And Reimbursements</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:to="lab_fsk_InvestmentCompanyExpenseRatioIncludingFeeWaiverAndReimbursements" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_KKRAlternativeAssetsL.P.Member_019e148e-2167-785f-8708-228da6a27286_terseLabel_en-US" xlink:label="lab_fsk_KKRAlternativeAssetsL.P.Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">KKR Alternative Assets L.P.</link:label>
    <link:label id="lab_fsk_KKRAlternativeAssetsL.P.Member_label_en-US" xlink:label="lab_fsk_KKRAlternativeAssetsL.P.Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">KKR Alternative Assets L.P. [Member]</link:label>
    <link:label id="lab_fsk_KKRAlternativeAssetsL.P.Member_documentation_en-US" xlink:label="lab_fsk_KKRAlternativeAssetsL.P.Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">KKR Alternative Assets L.P.</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_KKRAlternativeAssetsL.P.Member" xlink:href="fsk-20260331.xsd#fsk_KKRAlternativeAssetsL.P.Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_KKRAlternativeAssetsL.P.Member" xlink:to="lab_fsk_KKRAlternativeAssetsL.P.Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_MeadowbrookRunCreditFacilityMember_019d1bac-ccf8-7ad1-91ec-60e137609c40_terseLabel_en-US" xlink:label="lab_fsk_MeadowbrookRunCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Meadowbrook Run Credit Facility</link:label>
    <link:label id="lab_fsk_MeadowbrookRunCreditFacilityMember_label_en-US" xlink:label="lab_fsk_MeadowbrookRunCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Meadowbrook Run Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_MeadowbrookRunCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_MeadowbrookRunCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Meadowbrook Run Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_MeadowbrookRunCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_MeadowbrookRunCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_MeadowbrookRunCreditFacilityMember" xlink:to="lab_fsk_MeadowbrookRunCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AmortizationOfDebtDiscountPremium_019d1bac-ccf8-7443-8331-de685e1d77ef_terseLabel_en-US" xlink:label="lab_us-gaap_AmortizationOfDebtDiscountPremium" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amortization of Deferred Financing Costs and Discount / Premium</link:label>
    <link:label id="lab_us-gaap_AmortizationOfDebtDiscountPremium_label_en-US" xlink:label="lab_us-gaap_AmortizationOfDebtDiscountPremium" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amortization of Debt Discount (Premium)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AmortizationOfDebtDiscountPremium" xlink:to="lab_us-gaap_AmortizationOfDebtDiscountPremium" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InsuranceSectorMember_019d1bac-cbe9-7e8b-874f-8671d3ca5ce3_terseLabel_en-US" xlink:label="lab_us-gaap_InsuranceSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Insurance</link:label>
    <link:label id="lab_us-gaap_InsuranceSectorMember_label_en-US" xlink:label="lab_us-gaap_InsuranceSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Insurance Sector [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InsuranceSectorMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InsuranceSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InsuranceSectorMember" xlink:to="lab_us-gaap_InsuranceSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis_019d1bac-cc86-74eb-ad29-d1391069ef29_terseLabel_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cost basis of investments sold</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis_label_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt And Equity Securities, Sold, Cost Basis</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis_documentation_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt And Equity Securities, Sold, Cost Basis</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:href="fsk-20260331.xsd#fsk_DebtAndEquitySecuritiesSoldCostBasis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:to="lab_fsk_DebtAndEquitySecuritiesSoldCostBasis" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_DocumentType_019d1bac-cc86-7bda-a067-b40183283350_terseLabel_en-US" xlink:label="lab_dei_DocumentType" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Type</link:label>
    <link:label id="lab_dei_DocumentType_label_en-US" xlink:label="lab_dei_DocumentType" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Type</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_DocumentType" xlink:to="lab_dei_DocumentType" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueInputsLevel3Member_019d1bac-ccf8-7b04-82db-99f83a17d7ae_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel3Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Level 3&#8212;Significant unobservable inputs</link:label>
    <link:label id="lab_us-gaap_FairValueInputsLevel3Member_label_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel3Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Inputs, Level 3 [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueInputsLevel3Member" xlink:to="lab_us-gaap_FairValueInputsLevel3Member" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_OutstandingRecoveryIndName_terseLabel_en-US" xlink:label="lab_ecd_OutstandingRecoveryIndName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Name</link:label>
    <link:label id="lab_ecd_OutstandingRecoveryIndName_label_en-US" xlink:label="lab_ecd_OutstandingRecoveryIndName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding Recovery, Individual Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_OutstandingRecoveryIndName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_OutstandingRecoveryIndName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_OutstandingRecoveryIndName" xlink:to="lab_ecd_OutstandingRecoveryIndName" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentOwnedAtFairValueMember_019d689a-a880-71d9-aed8-856663f4f959_verboseLabel_en-US" xlink:label="lab_fsk_InvestmentOwnedAtFairValueMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Percentage of&#160;Portfolio</link:label>
    <link:label id="lab_fsk_InvestmentOwnedAtFairValueMember_019d1bac-cc86-7525-9803-1eb34e115064_terseLabel_en-US" xlink:label="lab_fsk_InvestmentOwnedAtFairValueMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of Portfolio</link:label>
    <link:label id="lab_fsk_InvestmentOwnedAtFairValueMember_label_en-US" xlink:label="lab_fsk_InvestmentOwnedAtFairValueMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, At Fair Value [Member]</link:label>
    <link:label id="lab_fsk_InvestmentOwnedAtFairValueMember_documentation_en-US" xlink:label="lab_fsk_InvestmentOwnedAtFairValueMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Owned, At Fair Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentOwnedAtFairValueMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentOwnedAtFairValueMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentOwnedAtFairValueMember" xlink:to="lab_fsk_InvestmentOwnedAtFairValueMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AdditionalPaidInCapital_019d1bac-cbe9-73b9-aabd-66e32ef4a50d_terseLabel_en-US" xlink:label="lab_us-gaap_AdditionalPaidInCapital" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital in excess of par value</link:label>
    <link:label id="lab_us-gaap_AdditionalPaidInCapital_label_en-US" xlink:label="lab_us-gaap_AdditionalPaidInCapital" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional Paid in Capital</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AdditionalPaidInCapital" xlink:to="lab_us-gaap_AdditionalPaidInCapital" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019d1bac-ccf8-7cb0-acf9-1b157c27f666_negatedTotalLabel_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:type="resource" xml:lang="en-US">Net Amount of Derivative Liabilities</link:label>
    <link:label id="lab_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_label_en-US" xlink:label="lab_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability, Including Not Subject to Master Netting Arrangement, after Offset and Deduction</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral" xlink:to="lab_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ProductOrServiceAxis_019d1bac-ccf8-76f6-8c9c-9a16abf07001_terseLabel_en-US" xlink:label="lab_srt_ProductOrServiceAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Product and Service [Axis]</link:label>
    <link:label id="lab_srt_ProductOrServiceAxis_label_en-US" xlink:label="lab_srt_ProductOrServiceAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product and Service [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ProductOrServiceAxis" xlink:to="lab_srt_ProductOrServiceAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeContractTypeDomain_019d1bac-ccf8-74c5-b3f5-8eb584ec1798_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeContractTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Contract [Domain]</link:label>
    <link:label id="lab_us-gaap_DerivativeContractTypeDomain_label_en-US" xlink:label="lab_us-gaap_DerivativeContractTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Contract [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeContractTypeDomain" xlink:to="lab_us-gaap_DerivativeContractTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A2.15ClassCNotesOutstandingMember_019d9f7d-7172-7f63-9205-ff345855debd_terseLabel_en-US" xlink:label="lab_fsk_A2.15ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2.15% Class C Notes Outstanding</link:label>
    <link:label id="lab_fsk_A2.15ClassCNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A2.15ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">2.15% Class C Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A2.15ClassCNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A2.15ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">2.15% Class C Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A2.15ClassCNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A2.15ClassCNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A2.15ClassCNotesOutstandingMember" xlink:to="lab_fsk_A2.15ClassCNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AllIndividualsMember_terseLabel_en-US" xlink:label="lab_ecd_AllIndividualsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Individuals</link:label>
    <link:label id="lab_ecd_AllIndividualsMember_label_en-US" xlink:label="lab_ecd_AllIndividualsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Individuals [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="lab_ecd_AllIndividualsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_KKRCreditAdvisorsUSLLCMember_019e14c1-2582-7927-94f7-4ee4d8c4984f_terseLabel_en-US" xlink:label="lab_fsk_KKRCreditAdvisorsUSLLCMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">KKR Credit Advisors (US) LLC</link:label>
    <link:label id="lab_fsk_KKRCreditAdvisorsUSLLCMember_label_en-US" xlink:label="lab_fsk_KKRCreditAdvisorsUSLLCMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">KKR Credit Advisors (US) LLC [Member]</link:label>
    <link:label id="lab_fsk_KKRCreditAdvisorsUSLLCMember_documentation_en-US" xlink:label="lab_fsk_KKRCreditAdvisorsUSLLCMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">KKR Credit Advisors (US) LLC</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_KKRCreditAdvisorsUSLLCMember" xlink:href="fsk-20260331.xsd#fsk_KKRCreditAdvisorsUSLLCMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_KKRCreditAdvisorsUSLLCMember" xlink:to="lab_fsk_KKRCreditAdvisorsUSLLCMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongtermDebtTypeDomain_019d1bac-cc86-7300-a792-0d4b3f1e4b12_terseLabel_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Type [Domain]</link:label>
    <link:label id="lab_us-gaap_LongtermDebtTypeDomain_label_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongtermDebtTypeDomain" xlink:to="lab_us-gaap_LongtermDebtTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock_019d1bac-cc86-70a8-8dcf-e0c293aa4cc6_terseLabel_en-US" xlink:label="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Supplemental Ratios</link:label>
    <link:label id="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock_label_en-US" xlink:label="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule Of Supplemental Ratios [Table Text Block]</link:label>
    <link:label id="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock_documentation_en-US" xlink:label="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule Of Supplemental Ratios</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:href="fsk-20260331.xsd#fsk_ScheduleOfSupplementalRatiosTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:to="lab_fsk_ScheduleOfSupplementalRatiosTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueDisclosuresAbstract_label_en-US" xlink:label="lab_us-gaap_FairValueDisclosuresAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Disclosures [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract" xlink:to="lab_us-gaap_FairValueDisclosuresAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember_019d8f02-580a-771d-94e3-daa42b2517eb_verboseLabel_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">CLO-2 Notes</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember_019d1bac-cbe9-7ed5-ac28-0467223731ee_terseLabel_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">CLO-1 Notes</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember_label_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligation Unsecured Notes [Member]</link:label>
    <link:label id="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember_documentation_en-US" xlink:label="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligation Unsecured Notes</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:href="fsk-20260331.xsd#fsk_CollateralizedLoanObligationUnsecuredNotesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:to="lab_fsk_CollateralizedLoanObligationUnsecuredNotesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount_019d1bac-cc86-7853-a50d-c57837e44151_terseLabel_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross investment income attributable to non-cash accretion of discount</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount_label_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable To Non-Cash Accretion Of Discount</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount_documentation_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable To Non-Cash Accretion Of Discount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:href="fsk-20260331.xsd#fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:to="lab_fsk_GrossInvestmentIncomePercentageAttributableToNonCashAccretionOfDiscount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock_019d1bac-cbe9-7bc9-a693-beef1bee5f0b_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Nonconsolidated Subsidiary Portfolio</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary, Summarized Financial Information [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock" xlink:to="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiarySummarizedFinancialInformationTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ForgoneRecoveryIndName_terseLabel_en-US" xlink:label="lab_ecd_ForgoneRecoveryIndName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Name</link:label>
    <link:label id="lab_ecd_ForgoneRecoveryIndName_label_en-US" xlink:label="lab_ecd_ForgoneRecoveryIndName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forgone Recovery, Individual Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ForgoneRecoveryIndName" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ForgoneRecoveryIndName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ForgoneRecoveryIndName" xlink:to="lab_ecd_ForgoneRecoveryIndName" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_019d1bac-cc86-76d5-af58-e2519adf9a50_negatedTotalLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:type="resource" xml:lang="en-US">Net decrease in net assets resulting from stockholder distributions (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution to Shareholders, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:to="lab_us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet_019d1bac-cbe9-79ed-a8bd-d90f082a9451_terseLabel_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net unrealized appreciation (depreciation)</link:label>
    <link:label id="lab_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet_label_en-US" xlink:label="lab_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Tax Basis, Unrealized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet" xlink:to="lab_us-gaap_TaxBasisOfInvestmentsUnrealizedAppreciationDepreciationNet" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_UnrealizedGainLossOnDerivatives_019d1bac-cc86-7962-88d4-806847643eb7_verboseLabel_en-US" xlink:label="lab_us-gaap_UnrealizedGainLossOnDerivatives" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized appreciation (depreciation) on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_UnrealizedGainLossOnDerivatives_019d1bac-cc86-745d-b5f8-e2cef2951376_terseLabel_en-US" xlink:label="lab_us-gaap_UnrealizedGainLossOnDerivatives" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized appreciation (depreciation) on foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_UnrealizedGainLossOnDerivatives_label_en-US" xlink:label="lab_us-gaap_UnrealizedGainLossOnDerivatives" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Gain (Loss) on Derivatives</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_UnrealizedGainLossOnDerivatives" xlink:to="lab_us-gaap_UnrealizedGainLossOnDerivatives" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A4125UnsecuredNotesDue2025Member_019d1bac-cc86-732b-8541-27ca39129be4_terseLabel_en-US" xlink:label="lab_fsk_A4125UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">4.125% Notes due 2025</link:label>
    <link:label id="lab_fsk_A4125UnsecuredNotesDue2025Member_label_en-US" xlink:label="lab_fsk_A4125UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">4.125% Unsecured Notes due 2025 [Member]</link:label>
    <link:label id="lab_fsk_A4125UnsecuredNotesDue2025Member_documentation_en-US" xlink:label="lab_fsk_A4125UnsecuredNotesDue2025Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">4.125% Unsecured Notes due 2025</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A4125UnsecuredNotesDue2025Member" xlink:href="fsk-20260331.xsd#fsk_A4125UnsecuredNotesDue2025Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A4125UnsecuredNotesDue2025Member" xlink:to="lab_fsk_A4125UnsecuredNotesDue2025Member" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_RangeAxis_019d1bac-cbe9-7a6d-8111-e6ed8a5951a8_terseLabel_en-US" xlink:label="lab_srt_RangeAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statistical Measurement [Axis]</link:label>
    <link:label id="lab_srt_RangeAxis_label_en-US" xlink:label="lab_srt_RangeAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statistical Measurement [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_RangeAxis" xlink:to="lab_srt_RangeAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember_terseLabel_en-US" xlink:label="lab_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested</link:label>
    <link:label id="lab_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember_label_en-US" xlink:label="lab_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember" xlink:to="lab_ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember_019d1bac-cc86-7b53-80fa-77838176d298_terseLabel_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized appreciation (depreciation)</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember_label_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Unrealized Gain (Loss) [Member]</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember_documentation_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Unrealized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:href="fsk-20260331.xsd#fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:to="lab_fsk_DebtAndEquitySecuritiesUnrealizedGainLossMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain_019d1bac-cc86-7dae-91c7-990171dfe0d3_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Domain]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain" xlink:to="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_StockRepurchaseProgramAuthorizedAmount1_019e1486-fb66-795c-bcab-14aba8e81208_terseLabel_en-US" xlink:label="lab_srt_StockRepurchaseProgramAuthorizedAmount1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amount authorized to repurchase</link:label>
    <link:label id="lab_srt_StockRepurchaseProgramAuthorizedAmount1_label_en-US" xlink:label="lab_srt_StockRepurchaseProgramAuthorizedAmount1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share Repurchase Program, Authorized, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_StockRepurchaseProgramAuthorizedAmount1" xlink:to="lab_srt_StockRepurchaseProgramAuthorizedAmount1" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtWeightedAverageInterestRate_019d1bac-cc86-7bc3-91d1-40409d393a8f_terseLabel_en-US" xlink:label="lab_us-gaap_DebtWeightedAverageInterestRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted average interest rate (as percent)</link:label>
    <link:label id="lab_us-gaap_DebtWeightedAverageInterestRate_label_en-US" xlink:label="lab_us-gaap_DebtWeightedAverageInterestRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt, Weighted Average Interest Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtWeightedAverageInterestRate" xlink:to="lab_us-gaap_DebtWeightedAverageInterestRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeFixedInterestRate_019d1bac-cc86-7e40-b92b-09ad1da04d4f_verboseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFixedInterestRate" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Company Receives</link:label>
    <link:label id="lab_us-gaap_DerivativeFixedInterestRate_019d1bac-cc86-7fdd-acdc-fab7467675de_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeFixedInterestRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fixed interest rate (as percent)</link:label>
    <link:label id="lab_us-gaap_DerivativeFixedInterestRate_label_en-US" xlink:label="lab_us-gaap_DerivativeFixedInterestRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative, Fixed Interest Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeFixedInterestRate" xlink:to="lab_us-gaap_DerivativeFixedInterestRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentForManagementFee_019d1bac-cc86-7280-a693-478b4b0b1860_terseLabel_en-US" xlink:label="lab_us-gaap_PaymentForManagementFee" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Base management fees</link:label>
    <link:label id="lab_us-gaap_PaymentForManagementFee_label_en-US" xlink:label="lab_us-gaap_PaymentForManagementFee" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payment for Management Fee</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForManagementFee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentForManagementFee"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentForManagementFee" xlink:to="lab_us-gaap_PaymentForManagementFee" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems_019d1bac-cc86-70ca-95e1-edc4c6bb3227_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Support for Nonconsolidated Legal Entity [Line Items]</link:label>
    <link:label id="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems_label_en-US" xlink:label="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Support for Nonconsolidated Legal Entity [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems" xlink:to="lab_us-gaap_FinancialSupportForNonconsolidatedLegalEntityLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019d1bac-ccf8-72c5-b05f-a99ea410bd3c_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Line Items]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AggtErrCompAmt_terseLabel_en-US" xlink:label="lab_ecd_AggtErrCompAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Erroneous Compensation Amount</link:label>
    <link:label id="lab_ecd_AggtErrCompAmt_label_en-US" xlink:label="lab_ecd_AggtErrCompAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Erroneous Compensation Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AggtErrCompAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AggtErrCompAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AggtErrCompAmt" xlink:to="lab_ecd_AggtErrCompAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_MaterialsSectorMember_019d1bac-cc86-7226-9ffe-f14a3e674ad4_terseLabel_en-US" xlink:label="lab_fsk_MaterialsSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Materials</link:label>
    <link:label id="lab_fsk_MaterialsSectorMember_label_en-US" xlink:label="lab_fsk_MaterialsSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Materials Sector [Member]</link:label>
    <link:label id="lab_fsk_MaterialsSectorMember_documentation_en-US" xlink:label="lab_fsk_MaterialsSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Materials Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_MaterialsSectorMember" xlink:href="fsk-20260331.xsd#fsk_MaterialsSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_MaterialsSectorMember" xlink:to="lab_fsk_MaterialsSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease_019e1496-f361-79bd-865c-1ed951ce3dd1_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Anniversay of issuance date that dividend rate will increase</link:label>
    <link:label id="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease_label_en-US" xlink:label="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Dividend Rate, Period Until Increase</link:label>
    <link:label id="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease_documentation_en-US" xlink:label="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Dividend Rate, Period Until Increase</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:href="fsk-20260331.xsd#fsk_PreferredStockDividendRatePeriodUntilIncrease"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:to="lab_fsk_PreferredStockDividendRatePeriodUntilIncrease" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeBasisSpreadOnVariableRate_019d1bac-ccf8-70d8-af7f-df626daca240_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Company Pays</link:label>
    <link:label id="lab_us-gaap_DerivativeBasisSpreadOnVariableRate_label_en-US" xlink:label="lab_us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative, Basis Spread on Variable Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeBasisSpreadOnVariableRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:to="lab_us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PeerGroupIssuersFnTextBlock_terseLabel_en-US" xlink:label="lab_ecd_PeerGroupIssuersFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Peer Group Issuers, Footnote</link:label>
    <link:label id="lab_ecd_PeerGroupIssuersFnTextBlock_label_en-US" xlink:label="lab_ecd_PeerGroupIssuersFnTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Peer Group Issuers, Footnote [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PeerGroupIssuersFnTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PeerGroupIssuersFnTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PeerGroupIssuersFnTextBlock" xlink:to="lab_ecd_PeerGroupIssuersFnTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum_019e14b9-fc6f-7e33-a57f-8c82eada0a03_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of demand requests</link:label>
    <link:label id="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum_label_en-US" xlink:label="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Registration Rights Agreement, Number Of Demand Requests, Maximum</link:label>
    <link:label id="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum_documentation_en-US" xlink:label="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Registration Rights Agreement, Number Of Demand Requests, Maximum</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:href="fsk-20260331.xsd#fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:to="lab_fsk_PreferredStockRegistrationRightsAgreementNumberOfDemandRequestsMaximum" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_JPMorganChaseBankMember_019d1bac-ccf8-74d9-9676-2d1fbc8d1383_terseLabel_en-US" xlink:label="lab_fsk_JPMorganChaseBankMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">JP Morgan Chase Bank</link:label>
    <link:label id="lab_fsk_JPMorganChaseBankMember_label_en-US" xlink:label="lab_fsk_JPMorganChaseBankMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">JP Morgan Chase Bank [Member]</link:label>
    <link:label id="lab_fsk_JPMorganChaseBankMember_documentation_en-US" xlink:label="lab_fsk_JPMorganChaseBankMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">JP Morgan Chase Bank</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_JPMorganChaseBankMember" xlink:href="fsk-20260331.xsd#fsk_JPMorganChaseBankMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_JPMorganChaseBankMember" xlink:to="lab_fsk_JPMorganChaseBankMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ErrCompAnalysisTextBlock_terseLabel_en-US" xlink:label="lab_ecd_ErrCompAnalysisTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Erroneous Compensation Analysis</link:label>
    <link:label id="lab_ecd_ErrCompAnalysisTextBlock_label_en-US" xlink:label="lab_ecd_ErrCompAnalysisTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Erroneous Compensation Analysis [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ErrCompAnalysisTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ErrCompAnalysisTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ErrCompAnalysisTextBlock" xlink:to="lab_ecd_ErrCompAnalysisTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ShareRepurchaseProgramDomain_019d1bac-ccf8-752b-8ba5-7dfbc7332110_terseLabel_en-US" xlink:label="lab_srt_ShareRepurchaseProgramDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share Repurchase Program [Domain]</link:label>
    <link:label id="lab_srt_ShareRepurchaseProgramDomain_label_en-US" xlink:label="lab_srt_ShareRepurchaseProgramDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share Repurchase Program [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ShareRepurchaseProgramDomain" xlink:to="lab_srt_ShareRepurchaseProgramDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnfundedEquityOtherCommitmentsMember_019d1bac-cc86-77dd-a49e-27a89fa19702_terseLabel_en-US" xlink:label="lab_fsk_UnfundedEquityOtherCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded Equity/Other Commitments</link:label>
    <link:label id="lab_fsk_UnfundedEquityOtherCommitmentsMember_label_en-US" xlink:label="lab_fsk_UnfundedEquityOtherCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unfunded Equity/Other commitments [Member]</link:label>
    <link:label id="lab_fsk_UnfundedEquityOtherCommitmentsMember_documentation_en-US" xlink:label="lab_fsk_UnfundedEquityOtherCommitmentsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unfunded Equity/Other commitments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnfundedEquityOtherCommitmentsMember" xlink:href="fsk-20260331.xsd#fsk_UnfundedEquityOtherCommitmentsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnfundedEquityOtherCommitmentsMember" xlink:to="lab_fsk_UnfundedEquityOtherCommitmentsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InterestRateSwapFourMember_019d1bac-cc86-7a7b-a54b-9c16a10fb1f0_terseLabel_en-US" xlink:label="lab_fsk_InterestRateSwapFourMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Four</link:label>
    <link:label id="lab_fsk_InterestRateSwapFourMember_label_en-US" xlink:label="lab_fsk_InterestRateSwapFourMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Four [Member]</link:label>
    <link:label id="lab_fsk_InterestRateSwapFourMember_documentation_en-US" xlink:label="lab_fsk_InterestRateSwapFourMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Four</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InterestRateSwapFourMember" xlink:href="fsk-20260331.xsd#fsk_InterestRateSwapFourMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InterestRateSwapFourMember" xlink:to="lab_fsk_InterestRateSwapFourMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeLiabilitiesAbstract_019d1bac-cbe9-77c6-a404-69599c5549bd_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeLiabilitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative Liability [Abstract]</link:label>
    <link:label id="lab_us-gaap_DerivativeLiabilitiesAbstract_label_en-US" xlink:label="lab_us-gaap_DerivativeLiabilitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeLiabilitiesAbstract" xlink:to="lab_us-gaap_DerivativeLiabilitiesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_GuaranteeObligationsNatureDomain_019e14d1-416b-7989-b826-99a4b7955443_terseLabel_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsNatureDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Guarantor Obligations, Nature [Domain]</link:label>
    <link:label id="lab_us-gaap_GuaranteeObligationsNatureDomain_label_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsNatureDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Guarantor Obligations, Nature [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain" xlink:to="lab_us-gaap_GuaranteeObligationsNatureDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock_019d1bac-ccf8-7a9e-b6a9-604dda802034_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Net Realized and Unrealized Gain (Loss) on Derivative Instruments</link:label>
    <link:label id="lab_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Instruments, Gain (Loss) [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock" xlink:to="lab_us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_Rule10b51ArrTrmntdFlag_terseLabel_en-US" xlink:label="lab_ecd_Rule10b51ArrTrmntdFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Rule 10b5-1 Arrangement Terminated</link:label>
    <link:label id="lab_ecd_Rule10b51ArrTrmntdFlag_label_en-US" xlink:label="lab_ecd_Rule10b51ArrTrmntdFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Rule 10b5-1 Arrangement Terminated [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_Rule10b51ArrTrmntdFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_Rule10b51ArrTrmntdFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_Rule10b51ArrTrmntdFlag" xlink:to="lab_ecd_Rule10b51ArrTrmntdFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_MediaEntertainmentSectorMember_019d1bac-cbe9-7fa5-9340-81610393c4a2_terseLabel_en-US" xlink:label="lab_fsk_MediaEntertainmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Media &amp; Entertainment</link:label>
    <link:label id="lab_fsk_MediaEntertainmentSectorMember_label_en-US" xlink:label="lab_fsk_MediaEntertainmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Media &amp; Entertainment Sector [Member]</link:label>
    <link:label id="lab_fsk_MediaEntertainmentSectorMember_documentation_en-US" xlink:label="lab_fsk_MediaEntertainmentSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Media &amp; Entertainment Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_MediaEntertainmentSectorMember" xlink:href="fsk-20260331.xsd#fsk_MediaEntertainmentSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_MediaEntertainmentSectorMember" xlink:to="lab_fsk_MediaEntertainmentSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LineOfCredit_019d1bac-ccf8-7c71-9c5b-ec7a2fc8e46d_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCredit" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term line of credit</link:label>
    <link:label id="lab_us-gaap_LineOfCredit_label_en-US" xlink:label="lab_us-gaap_LineOfCredit" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Line of Credit</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCredit" xlink:to="lab_us-gaap_LineOfCredit" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueInputsLevel1Member_019d1bac-cc86-7aa6-8fa9-74c37fbd7629_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel1Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Level 1&#8212;Price quotations in active markets</link:label>
    <link:label id="lab_us-gaap_FairValueInputsLevel1Member_label_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel1Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Inputs, Level 1 [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueInputsLevel1Member" xlink:to="lab_us-gaap_FairValueInputsLevel1Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SoftwareServicesSectorMember_019d1bac-cc86-7f2e-a8b5-5fa518388395_terseLabel_en-US" xlink:label="lab_fsk_SoftwareServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Software &amp; Services</link:label>
    <link:label id="lab_fsk_SoftwareServicesSectorMember_label_en-US" xlink:label="lab_fsk_SoftwareServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Software &amp; Services Sector [Member]</link:label>
    <link:label id="lab_fsk_SoftwareServicesSectorMember_documentation_en-US" xlink:label="lab_fsk_SoftwareServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Software &amp; Services Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SoftwareServicesSectorMember" xlink:href="fsk-20260331.xsd#fsk_SoftwareServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SoftwareServicesSectorMember" xlink:to="lab_fsk_SoftwareServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019d1bac-ccf8-75b4-9447-acbcf2820e29_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_label_en-US" xlink:label="lab_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="lab_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EarningsPerShareDiluted_019d1bac-cc86-7a91-ac85-294cf63c9faf_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerShareDiluted" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from operations (Earnings (Losses) per Share) - diluted (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_EarningsPerShareDiluted_label_en-US" xlink:label="lab_us-gaap_EarningsPerShareDiluted" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share, Diluted</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EarningsPerShareDiluted" xlink:to="lab_us-gaap_EarningsPerShareDiluted" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ScenarioForecastMember_019e14c2-c258-7439-860f-ae2b7999ce94_terseLabel_en-US" xlink:label="lab_srt_ScenarioForecastMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Forecast</link:label>
    <link:label id="lab_srt_ScenarioForecastMember_label_en-US" xlink:label="lab_srt_ScenarioForecastMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forecast [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ScenarioForecastMember" xlink:to="lab_srt_ScenarioForecastMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities_019d1bac-cbe9-7fa1-8242-c016037b9d5b_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in other accrued expenses and liabilities</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Other Accrued Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherAccruedLiabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities" xlink:to="lab_us-gaap_IncreaseDecreaseInOtherAccruedLiabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ErrCompRecoveryTable_terseLabel_en-US" xlink:label="lab_ecd_ErrCompRecoveryTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Erroneously Awarded Compensation Recovery</link:label>
    <link:label id="lab_ecd_ErrCompRecoveryTable_label_en-US" xlink:label="lab_ecd_ErrCompRecoveryTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Erroneously Awarded Compensation Recovery [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ErrCompRecoveryTable" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ErrCompRecoveryTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ErrCompRecoveryTable" xlink:to="lab_ecd_ErrCompRecoveryTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ConcentrationRiskBenchmarkDomain_019d1bac-cc86-7dcc-89ca-f9fc9b2fd49c_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskBenchmarkDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Domain]</link:label>
    <link:label id="lab_us-gaap_ConcentrationRiskBenchmarkDomain_label_en-US" xlink:label="lab_us-gaap_ConcentrationRiskBenchmarkDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk Benchmark [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="lab_us-gaap_ConcentrationRiskBenchmarkDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestIncomeOperating_019d1bac-cc86-7c45-acf7-eca606ef3538_terseLabel_en-US" xlink:label="lab_us-gaap_InterestIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Income</link:label>
    <link:label id="lab_us-gaap_InterestIncomeOperating_label_en-US" xlink:label="lab_us-gaap_InterestIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Income, Operating</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperating" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOperating"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestIncomeOperating" xlink:to="lab_us-gaap_InterestIncomeOperating" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_Security12bTitle_019d1bac-cc86-73f2-aefc-1d5644794615_terseLabel_en-US" xlink:label="lab_dei_Security12bTitle" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Title of 12(b) Security</link:label>
    <link:label id="lab_dei_Security12bTitle_label_en-US" xlink:label="lab_dei_Security12bTitle" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Title of 12(b) Security</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_Security12bTitle" xlink:to="lab_dei_Security12bTitle" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DividendsAxis_019d1bac-cc86-7cad-a688-4e8b9284ccea_terseLabel_en-US" xlink:label="lab_us-gaap_DividendsAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Dividends [Axis]</link:label>
    <link:label id="lab_us-gaap_DividendsAxis_label_en-US" xlink:label="lab_us-gaap_DividendsAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Dividends [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DividendsAxis" xlink:to="lab_us-gaap_DividendsAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_019d1bac-cbe9-7640-8171-ab5b911a77c7_terseLabel_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock repurchased and distributed</link:label>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_label_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Value, Dividend Reinvestment Plan</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:to="lab_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EarningsPerShareAbstract_019d1bac-cc86-7637-af42-0ff25a2c6b7d_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerShareAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Per share information&#8212;basic and diluted</link:label>
    <link:label id="lab_us-gaap_EarningsPerShareAbstract_label_en-US" xlink:label="lab_us-gaap_EarningsPerShareAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EarningsPerShareAbstract" xlink:to="lab_us-gaap_EarningsPerShareAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019d1bac-cbe9-7571-b202-0da4948f7857_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net investment income</link:label>
    <link:label id="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_019d1bac-cbe9-75f7-a09c-04974bd4777d_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net investment income (loss)</link:label>
    <link:label id="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax_label_en-US" xlink:label="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Income, Operating, after Expense and Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:to="lab_us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A2625UnsecuredNotesDue2027Member_019d1bac-cc86-7da0-8bc6-9b5a1824601f_terseLabel_en-US" xlink:label="lab_fsk_A2625UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2.625% Notes due 2027</link:label>
    <link:label id="lab_fsk_A2625UnsecuredNotesDue2027Member_label_en-US" xlink:label="lab_fsk_A2625UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">2.625% Unsecured Notes due 2027 [Member]</link:label>
    <link:label id="lab_fsk_A2625UnsecuredNotesDue2027Member_documentation_en-US" xlink:label="lab_fsk_A2625UnsecuredNotesDue2027Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">2.625% Unsecured Notes due 2027</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A2625UnsecuredNotesDue2027Member" xlink:href="fsk-20260331.xsd#fsk_A2625UnsecuredNotesDue2027Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A2625UnsecuredNotesDue2027Member" xlink:to="lab_fsk_A2625UnsecuredNotesDue2027Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage_019e14b2-a51b-7dcc-8bfd-ae6a46d255aa_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Beneficial ownership percentage</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage_label_en-US" xlink:label="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Beneficial Ownership, Percentage</link:label>
    <link:label id="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage_documentation_en-US" xlink:label="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Convertible, Beneficial Ownership, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:href="fsk-20260331.xsd#fsk_PreferredStockConvertibleBeneficialOwnershipPercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:to="lab_fsk_PreferredStockConvertibleBeneficialOwnershipPercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FoodBeverageTobaccoSectorMember_019d1bac-ccf8-793a-acc9-4fe45805027e_terseLabel_en-US" xlink:label="lab_fsk_FoodBeverageTobaccoSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Food, Beverage &amp; Tobacco</link:label>
    <link:label id="lab_fsk_FoodBeverageTobaccoSectorMember_label_en-US" xlink:label="lab_fsk_FoodBeverageTobaccoSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Food, Beverage &amp; Tobacco Sector [Member]</link:label>
    <link:label id="lab_fsk_FoodBeverageTobaccoSectorMember_documentation_en-US" xlink:label="lab_fsk_FoodBeverageTobaccoSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Food, Beverage &amp; Tobacco Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FoodBeverageTobaccoSectorMember" xlink:href="fsk-20260331.xsd#fsk_FoodBeverageTobaccoSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FoodBeverageTobaccoSectorMember" xlink:to="lab_fsk_FoodBeverageTobaccoSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets_019d1bac-cc86-74b0-b1c6-fc46f6140b0a_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio of interest expense to average net assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets_label_en-US" xlink:label="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Interest Expense To Average Net Assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Interest Expense To Average Net Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyInterestExpenseToAverageNetAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:to="lab_fsk_InvestmentCompanyInterestExpenseToAverageNetAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable_019d1bac-cbe9-7a66-879d-f00403549a13_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Table]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Nonconsolidated Subsidiary [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable" xlink:to="lab_us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember_019d1bac-ccf8-7203-8167-b17e9d92ac2a_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Realized Capital Gains</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Realized Capital Gains [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Realized Capital Gains</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateRealizedCapitalGainsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_OtherSeniorSecuredDebtMember_019d1bac-cc86-7d40-9893-c3a0ba77827d_terseLabel_en-US" xlink:label="lab_fsk_OtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Senior Secured Debt</link:label>
    <link:label id="lab_fsk_OtherSeniorSecuredDebtMember_label_en-US" xlink:label="lab_fsk_OtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Senior Secured Debt [Member]</link:label>
    <link:label id="lab_fsk_OtherSeniorSecuredDebtMember_documentation_en-US" xlink:label="lab_fsk_OtherSeniorSecuredDebtMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Other Senior Secured Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_OtherSeniorSecuredDebtMember" xlink:href="fsk-20260331.xsd#fsk_OtherSeniorSecuredDebtMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_OtherSeniorSecuredDebtMember" xlink:to="lab_fsk_OtherSeniorSecuredDebtMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived_019d1bac-cc86-72b3-9aa2-2b2db3ad2a4d_terseLabel_en-US" xlink:label="lab_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Federal income taxes paid during the period</link:label>
    <link:label id="lab_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived_label_en-US" xlink:label="lab_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Paid, Federal, before Refund Received</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidFederalBeforeRefundReceived"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived" xlink:to="lab_us-gaap_IncomeTaxPaidFederalBeforeRefundReceived" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInCash_019d1bac-ccf8-7c3e-b127-9ca7f59de440_terseLabel_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInCash" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest income</link:label>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInCash_label_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInCash" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Income, Operating, Paid in Cash</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperatingPaidInCash" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOperatingPaidInCash"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestIncomeOperatingPaidInCash" xlink:to="lab_us-gaap_InterestIncomeOperatingPaidInCash" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AdministrativeFeesExpense_019d1bac-cc86-7883-93c5-d9ccaa6d948e_terseLabel_en-US" xlink:label="lab_us-gaap_AdministrativeFeesExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accounting and administrative fees</link:label>
    <link:label id="lab_us-gaap_AdministrativeFeesExpense_019d1bac-cc86-7a65-a560-f2ceefbed055_verboseLabel_en-US" xlink:label="lab_us-gaap_AdministrativeFeesExpense" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Administrative Services Expenses</link:label>
    <link:label id="lab_us-gaap_AdministrativeFeesExpense_label_en-US" xlink:label="lab_us-gaap_AdministrativeFeesExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Administrative Fees Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdministrativeFeesExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdministrativeFeesExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AdministrativeFeesExpense" xlink:to="lab_us-gaap_AdministrativeFeesExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A3400UnsecuredNotesDue2026Member_019d1bac-cc86-7161-b307-0d93ba4d940c_terseLabel_en-US" xlink:label="lab_fsk_A3400UnsecuredNotesDue2026Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">3.400% Notes due 2026</link:label>
    <link:label id="lab_fsk_A3400UnsecuredNotesDue2026Member_label_en-US" xlink:label="lab_fsk_A3400UnsecuredNotesDue2026Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">3.400% Unsecured Notes due 2026 [Member]</link:label>
    <link:label id="lab_fsk_A3400UnsecuredNotesDue2026Member_documentation_en-US" xlink:label="lab_fsk_A3400UnsecuredNotesDue2026Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">3.400% Unsecured Notes due 2026</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A3400UnsecuredNotesDue2026Member" xlink:href="fsk-20260331.xsd#fsk_A3400UnsecuredNotesDue2026Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A3400UnsecuredNotesDue2026Member" xlink:to="lab_fsk_A3400UnsecuredNotesDue2026Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019d1bac-ccf8-7a34-ae46-8f6298a2b42f_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from sale of investments</link:label>
    <link:label id="lab_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_label_en-US" xlink:label="lab_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from Sale of Equity Securities, FV-NI</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi" xlink:to="lab_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashHeldInForeignCurrency_019d1bac-cc86-7af1-acd0-8e57d3e14adf_terseLabel_en-US" xlink:label="lab_us-gaap_CashHeldInForeignCurrency" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Foreign currency, at fair value (cost&#8212;$5 and $27, respectively)</link:label>
    <link:label id="lab_us-gaap_CashHeldInForeignCurrency_019df364-865f-725c-8e5c-2c6b21d4cc63_verboseLabel_en-US" xlink:label="lab_us-gaap_CashHeldInForeignCurrency" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Foreign currency</link:label>
    <link:label id="lab_us-gaap_CashHeldInForeignCurrency_label_en-US" xlink:label="lab_us-gaap_CashHeldInForeignCurrency" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalent, Held in Foreign Currency</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashHeldInForeignCurrency" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashHeldInForeignCurrency"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashHeldInForeignCurrency" xlink:to="lab_us-gaap_CashHeldInForeignCurrency" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019d1bac-cc86-719c-820e-b30bfdb27e71_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TreasuryStockSharesAcquired_019d1bac-cc86-7152-ab46-e53a111d0585_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_TreasuryStockSharesAcquired" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Share Repurchase Program (in shares)</link:label>
    <link:label id="lab_us-gaap_TreasuryStockSharesAcquired_label_en-US" xlink:label="lab_us-gaap_TreasuryStockSharesAcquired" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Treasury Stock, Shares, Acquired</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TreasuryStockSharesAcquired" xlink:to="lab_us-gaap_TreasuryStockSharesAcquired" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialServicesSectorMember_019d1bac-cc86-7af6-b440-1a4014f4f3c9_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Services</link:label>
    <link:label id="lab_us-gaap_FinancialServicesSectorMember_label_en-US" xlink:label="lab_us-gaap_FinancialServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Services Sector [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialServicesSectorMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialServicesSectorMember" xlink:to="lab_us-gaap_FinancialServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2031Member_019d1bac-cc86-7a2e-b60f-eac09fe5bca7_terseLabel_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2031Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">6.125% Unsecured Notes due 2031</link:label>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2031Member_019d1bac-cc86-7619-9afd-5675488def46_verboseLabel_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2031Member" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">6.125% Notes due 2031</link:label>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2031Member_label_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2031Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">6.125% Unsecured Notes due 2031 [Member]</link:label>
    <link:label id="lab_fsk_A6.125UnsecuredNotesDue2031Member_documentation_en-US" xlink:label="lab_fsk_A6.125UnsecuredNotesDue2031Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">6.125% Unsecured Notes due 2031</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A6.125UnsecuredNotesDue2031Member" xlink:href="fsk-20260331.xsd#fsk_A6.125UnsecuredNotesDue2031Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A6.125UnsecuredNotesDue2031Member" xlink:to="lab_fsk_A6.125UnsecuredNotesDue2031Member" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare_019d1bac-ccf8-70c5-a15f-cbb4ab1d7e58_totalLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from capital share transactions (in dollars per share)</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare_label_en-US" xlink:label="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Capital Share Transaction, Per Share</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Capital Share Transaction, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyCapitalShareTransactionPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:to="lab_fsk_InvestmentCompanyCapitalShareTransactionPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardTmgDiscLineItems_label_en-US" xlink:label="lab_ecd_AwardTmgDiscLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Award Timing Disclosures [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardTmgDiscLineItems" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardTmgDiscLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardTmgDiscLineItems" xlink:to="lab_ecd_AwardTmgDiscLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_StockholmInterbankOfferedRateMember_019d1bac-cc86-7771-8691-898e1154164c_terseLabel_en-US" xlink:label="lab_fsk_StockholmInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">STIBOR</link:label>
    <link:label id="lab_fsk_StockholmInterbankOfferedRateMember_label_en-US" xlink:label="lab_fsk_StockholmInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stockholm Interbank Offered Rate [Member]</link:label>
    <link:label id="lab_fsk_StockholmInterbankOfferedRateMember_documentation_en-US" xlink:label="lab_fsk_StockholmInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Stockholm Interbank Offered Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_StockholmInterbankOfferedRateMember" xlink:href="fsk-20260331.xsd#fsk_StockholmInterbankOfferedRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_StockholmInterbankOfferedRateMember" xlink:to="lab_fsk_StockholmInterbankOfferedRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember_019d1bac-cc86-75ff-8c46-4d5e4fc3aacc_terseLabel_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Less Than</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember_label_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Less Than [Member]</link:label>
    <link:label id="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember_documentation_en-US" xlink:label="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Lender Other Than Non-Extending Lenders, Alternate Base Rate, Less Than</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:href="fsk-20260331.xsd#fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:to="lab_fsk_LenderOtherThanNonExtendingLendersAlternateBaseRateLessThanMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtInstrumentCarryingAmount_019d1bac-cc86-7ade-864d-c3d321bf158d_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentCarryingAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long term outstanding</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentCarryingAmount_019d1bac-cc86-730b-8ebd-ae537400afeb_verboseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentCarryingAmount" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Total amount of senior securities outstanding, exclusive of treasury securities</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentCarryingAmount_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentCarryingAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Gross</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount" xlink:to="lab_us-gaap_DebtInstrumentCarryingAmount" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract_019d1bac-ccf8-7f6e-a3a0-88a3bd88895b_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Results of operations</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Investment Income (Loss) from Operations, Per Share [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract" xlink:to="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShareAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_SubsidiariesMember_019d1bac-cbe9-73c8-aa1c-64f494b84126_terseLabel_en-US" xlink:label="lab_srt_SubsidiariesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsidiaries</link:label>
    <link:label id="lab_srt_SubsidiariesMember_label_en-US" xlink:label="lab_srt_SubsidiariesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsidiaries [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SubsidiariesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_SubsidiariesMember" xlink:to="lab_srt_SubsidiariesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentBasisSpreadVariableRate_019d1bac-cc86-70aa-91bd-4167782691af_verboseLabel_en-US" xlink:label="lab_us-gaap_InvestmentBasisSpreadVariableRate" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Variable rate (as percent)</link:label>
    <link:label id="lab_us-gaap_InvestmentBasisSpreadVariableRate_label_en-US" xlink:label="lab_us-gaap_InvestmentBasisSpreadVariableRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment, Basis Spread, Variable Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentBasisSpreadVariableRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentBasisSpreadVariableRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentBasisSpreadVariableRate" xlink:to="lab_us-gaap_InvestmentBasisSpreadVariableRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockholdersEquityNoteDisclosureTextBlock_019d1bac-cbe9-7294-940d-ee3d6ebc6262_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share Transactions</link:label>
    <link:label id="lab_us-gaap_StockholdersEquityNoteDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:to="lab_us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance_019e14b0-2325-763d-9539-d2069cfc03fb_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Period following issuance that restricts selling, pledging, transfer, and disposal of shares</link:label>
    <link:label id="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance_label_en-US" xlink:label="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Restriction On Selling, Transfer, Or Disposal, Period Following Issuance</link:label>
    <link:label id="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance_documentation_en-US" xlink:label="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Restriction On Selling, Transfer, Or Disposal, Period Following Issuance</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:href="fsk-20260331.xsd#fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:to="lab_fsk_PreferredStockRestrictionOnSellingTransferOrDisposalPeriodFollowingIssuance" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentOwnedBalanceShares_019d1bac-ccf8-78c6-917f-67eea1c47cd2_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentOwnedBalanceShares" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Principal (in shares)</link:label>
    <link:label id="lab_us-gaap_InvestmentOwnedBalanceShares_label_en-US" xlink:label="lab_us-gaap_InvestmentOwnedBalanceShares" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Owned, Balance, Shares</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedBalanceShares" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentOwnedBalanceShares"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentOwnedBalanceShares" xlink:to="lab_us-gaap_InvestmentOwnedBalanceShares" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetIncomeLoss_019d1bac-cc86-74c1-b6eb-a3cc56bb5ae9_totalLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from operations</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_019d1bac-cc86-74f9-9ebf-21d47fc5b95d_terseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net increase (decrease) in net assets resulting from operations</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_label_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss) Attributable to Parent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetIncomeLoss" xlink:to="lab_us-gaap_NetIncomeLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventTable_019d1bac-cbe9-7f34-a235-854ef10d4260_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Event [Table]</link:label>
    <link:label id="lab_us-gaap_SubsequentEventTable_label_en-US" xlink:label="lab_us-gaap_SubsequentEventTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventTable" xlink:to="lab_us-gaap_SubsequentEventTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DividendsDomain_019d1bac-cc86-7639-93ff-aa99053cced5_terseLabel_en-US" xlink:label="lab_us-gaap_DividendsDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Dividends [Domain]</link:label>
    <link:label id="lab_us-gaap_DividendsDomain_label_en-US" xlink:label="lab_us-gaap_DividendsDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Dividends [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DividendsDomain" xlink:to="lab_us-gaap_DividendsDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrExpirationDate_terseLabel_en-US" xlink:label="lab_ecd_TrdArrExpirationDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Expiration Date</link:label>
    <link:label id="lab_ecd_TrdArrExpirationDate_label_en-US" xlink:label="lab_ecd_TrdArrExpirationDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement Expiration Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrExpirationDate" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrExpirationDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrExpirationDate" xlink:to="lab_ecd_TrdArrExpirationDate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CollateralizedLoanObligationsMember_019d1bac-cc86-792e-86da-0b48428be4ae_terseLabel_en-US" xlink:label="lab_us-gaap_CollateralizedLoanObligationsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligation</link:label>
    <link:label id="lab_us-gaap_CollateralizedLoanObligationsMember_label_en-US" xlink:label="lab_us-gaap_CollateralizedLoanObligationsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Collateralized Loan Obligations [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedLoanObligationsMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralizedLoanObligationsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CollateralizedLoanObligationsMember" xlink:to="lab_us-gaap_CollateralizedLoanObligationsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_019d1bac-cc86-762b-bc61-6dac0cac85b1_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net investment income (loss) (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Investment Income (Loss), Per Share, Basic</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:to="lab_us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_VariableRateComponentAxis_019e0884-2433-7473-aa54-6d67415a21a3_terseLabel_en-US" xlink:label="lab_fsk_VariableRateComponentAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable Rate Component [Member]</link:label>
    <link:label id="lab_fsk_VariableRateComponentAxis_label_en-US" xlink:label="lab_fsk_VariableRateComponentAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate Component [Axis]</link:label>
    <link:label id="lab_fsk_VariableRateComponentAxis_documentation_en-US" xlink:label="lab_fsk_VariableRateComponentAxis" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Variable Rate Component</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_VariableRateComponentAxis" xlink:href="fsk-20260331.xsd#fsk_VariableRateComponentAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_VariableRateComponentAxis" xlink:to="lab_fsk_VariableRateComponentAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_StructuringFeesMember_019d1bac-cc86-7c08-aab1-4d68d0de3744_terseLabel_en-US" xlink:label="lab_fsk_StructuringFeesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Structuring Fees</link:label>
    <link:label id="lab_fsk_StructuringFeesMember_label_en-US" xlink:label="lab_fsk_StructuringFeesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Structuring Fees [Member]</link:label>
    <link:label id="lab_fsk_StructuringFeesMember_documentation_en-US" xlink:label="lab_fsk_StructuringFeesMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Structuring Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_StructuringFeesMember" xlink:href="fsk-20260331.xsd#fsk_StructuringFeesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_StructuringFeesMember" xlink:to="lab_fsk_StructuringFeesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInKind_019d1bac-ccf8-7360-ba08-3a931c5eb7ef_terseLabel_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInKind" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Paid-in-kind interest income</link:label>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInKind_019d1bac-ccf8-7361-bdf6-05b01a750931_negatedNetLabel_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInKind" xlink:role="http://www.xbrl.org/2009/role/negatedNetLabel" xlink:type="resource" xml:lang="en-US">Paid-in-kind interest</link:label>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInKind_019d1bac-ccf8-7593-9ce3-10ff806e414c_verboseLabel_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInKind" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">PIK Income</link:label>
    <link:label id="lab_us-gaap_InterestIncomeOperatingPaidInKind_label_en-US" xlink:label="lab_us-gaap_InterestIncomeOperatingPaidInKind" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Income, Operating, Paid in Kind</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperatingPaidInKind" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOperatingPaidInKind"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestIncomeOperatingPaidInKind" xlink:to="lab_us-gaap_InterestIncomeOperatingPaidInKind" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings_019d1bac-cc86-71bc-9f6f-7247a69af0e1_negatedTerseLabel_en-US" xlink:label="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Net change in unrealized (appreciation) depreciation on foreign currency translation</link:label>
    <link:label id="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings_label_en-US" xlink:label="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Currency Transaction Gain (Loss), Unrealized Gain (Loss) On Borrowings</link:label>
    <link:label id="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings_documentation_en-US" xlink:label="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Foreign Currency Transaction Gain (Loss), Unrealized Gain (Loss) On Borrowings</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:href="fsk-20260331.xsd#fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:to="lab_fsk_ForeignCurrencyTransactionGainLossUnrealizedGainLossOnBorrowings" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtInstrumentBorrowingRateTestThreshold_019d1bac-cbe9-7208-ae3f-79b0289239af_terseLabel_en-US" xlink:label="lab_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing rate test threshold</link:label>
    <link:label id="lab_fsk_DebtInstrumentBorrowingRateTestThreshold_label_en-US" xlink:label="lab_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Borrowing Rate Test Threshold</link:label>
    <link:label id="lab_fsk_DebtInstrumentBorrowingRateTestThreshold_documentation_en-US" xlink:label="lab_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Instrument, Borrowing Rate Test Threshold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:href="fsk-20260331.xsd#fsk_DebtInstrumentBorrowingRateTestThreshold"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:to="lab_fsk_DebtInstrumentBorrowingRateTestThreshold" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentsMember_019d1bac-cc86-780b-8c9a-2f54c6040d3a_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments</link:label>
    <link:label id="lab_us-gaap_InvestmentsMember_label_en-US" xlink:label="lab_us-gaap_InvestmentsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentsMember" xlink:to="lab_us-gaap_InvestmentsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PreferredStockSharesAuthorized_019d1bac-cc86-7d00-b2ef-711560fcfce4_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, shares authorized (in shares)</link:label>
    <link:label id="lab_us-gaap_PreferredStockSharesAuthorized_label_en-US" xlink:label="lab_us-gaap_PreferredStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Shares Authorized</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PreferredStockSharesAuthorized" xlink:to="lab_us-gaap_PreferredStockSharesAuthorized" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrAdoptionDate_terseLabel_en-US" xlink:label="lab_ecd_TrdArrAdoptionDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adoption Date</link:label>
    <link:label id="lab_ecd_TrdArrAdoptionDate_label_en-US" xlink:label="lab_ecd_TrdArrAdoptionDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement Adoption Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrAdoptionDate" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrAdoptionDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrAdoptionDate" xlink:to="lab_ecd_TrdArrAdoptionDate" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InterestRateSwapThreeMember_019d1bac-cc86-7c88-88ef-265f38d6ed4e_terseLabel_en-US" xlink:label="lab_fsk_InterestRateSwapThreeMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Three</link:label>
    <link:label id="lab_fsk_InterestRateSwapThreeMember_label_en-US" xlink:label="lab_fsk_InterestRateSwapThreeMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Three [Member]</link:label>
    <link:label id="lab_fsk_InterestRateSwapThreeMember_documentation_en-US" xlink:label="lab_fsk_InterestRateSwapThreeMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Swap Three</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InterestRateSwapThreeMember" xlink:href="fsk-20260331.xsd#fsk_InterestRateSwapThreeMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InterestRateSwapThreeMember" xlink:to="lab_fsk_InterestRateSwapThreeMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_CompActuallyPaidVsNetIncomeTextBlock_terseLabel_en-US" xlink:label="lab_ecd_CompActuallyPaidVsNetIncomeTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Net Income</link:label>
    <link:label id="lab_ecd_CompActuallyPaidVsNetIncomeTextBlock_label_en-US" xlink:label="lab_ecd_CompActuallyPaidVsNetIncomeTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Compensation Actually Paid vs. Net Income [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_CompActuallyPaidVsNetIncomeTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_CompActuallyPaidVsNetIncomeTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_CompActuallyPaidVsNetIncomeTextBlock" xlink:to="lab_ecd_CompActuallyPaidVsNetIncomeTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityCurrentReportingStatus_019d1bac-ccf8-785e-a31c-56dbc8b4d34c_terseLabel_en-US" xlink:label="lab_dei_EntityCurrentReportingStatus" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Current Reporting Status</link:label>
    <link:label id="lab_dei_EntityCurrentReportingStatus_label_en-US" xlink:label="lab_dei_EntityCurrentReportingStatus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Current Reporting Status</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityCurrentReportingStatus" xlink:to="lab_dei_EntityCurrentReportingStatus" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock_019d1bac-cc86-7564-98b8-e915057cfa3f_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Investments</link:label>
    <link:label id="lab_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock_label_en-US" xlink:label="lab_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Holdings, Schedule of Investments [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock" xlink:to="lab_us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ManagementAndServiceFeesIncentiveRate_019d1bac-cbe9-701a-b918-6da33bad5b75_terseLabel_en-US" xlink:label="lab_us-gaap_ManagementAndServiceFeesIncentiveRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Incentive fee (as percent)</link:label>
    <link:label id="lab_us-gaap_ManagementAndServiceFeesIncentiveRate_label_en-US" xlink:label="lab_us-gaap_ManagementAndServiceFeesIncentiveRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Management and Service Fees, Incentive Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementAndServiceFeesIncentiveRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementAndServiceFeesIncentiveRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ManagementAndServiceFeesIncentiveRate" xlink:to="lab_us-gaap_ManagementAndServiceFeesIncentiveRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeLineItems_019d1bac-cc86-73de-a7b6-ff59ee25aeb8_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivative [Line Items]</link:label>
    <link:label id="lab_us-gaap_DerivativeLineItems_label_en-US" xlink:label="lab_us-gaap_DerivativeLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeLineItems" xlink:to="lab_us-gaap_DerivativeLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscTable_terseLabel_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Awards Close in Time to MNPI Disclosures</link:label>
    <link:label id="lab_ecd_AwardsCloseToMnpiDiscTable_label_en-US" xlink:label="lab_ecd_AwardsCloseToMnpiDiscTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Awards Close in Time to MNPI Disclosures [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AwardsCloseToMnpiDiscTable" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AwardsCloseToMnpiDiscTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AwardsCloseToMnpiDiscTable" xlink:to="lab_ecd_AwardsCloseToMnpiDiscTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansFirstLienMember_019d1bac-ccf8-729f-a8d5-de1e776af58b_terseLabel_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Funded, Senior Secured Loans&#8212;First Lien</link:label>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansFirstLienMember_label_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Funded, Senior&#160;Secured Loans, First Lien [Member]</link:label>
    <link:label id="lab_fsk_FundedSeniorSecuredLoansFirstLienMember_documentation_en-US" xlink:label="lab_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Securities, Senior&#160;Secured Loans&#8212;First Lien [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:href="fsk-20260331.xsd#fsk_FundedSeniorSecuredLoansFirstLienMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:to="lab_fsk_FundedSeniorSecuredLoansFirstLienMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LineOfCreditMember_019d1bac-cc86-7969-9c6b-ccca42d13948_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of Credit</link:label>
    <link:label id="lab_us-gaap_LineOfCreditMember_label_en-US" xlink:label="lab_us-gaap_LineOfCreditMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditMember" xlink:to="lab_us-gaap_LineOfCreditMember" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ConsolidatedEntitiesDomain_019d1bac-cbe9-7243-8e9f-e855f6dd0069_terseLabel_en-US" xlink:label="lab_srt_ConsolidatedEntitiesDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consolidated Entities [Domain]</link:label>
    <link:label id="lab_srt_ConsolidatedEntitiesDomain_label_en-US" xlink:label="lab_srt_ConsolidatedEntitiesDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consolidated Entities [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ConsolidatedEntitiesDomain" xlink:to="lab_srt_ConsolidatedEntitiesDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OffsettingLiabilitiesTableTextBlock_019d1bac-cc86-79e7-bce8-953397acb188_terseLabel_en-US" xlink:label="lab_us-gaap_OffsettingLiabilitiesTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Offsetting Liabilities</link:label>
    <link:label id="lab_us-gaap_OffsettingLiabilitiesTableTextBlock_label_en-US" xlink:label="lab_us-gaap_OffsettingLiabilitiesTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Offsetting Liabilities [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffsettingLiabilitiesTableTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffsettingLiabilitiesTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OffsettingLiabilitiesTableTextBlock" xlink:to="lab_us-gaap_OffsettingLiabilitiesTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RetainedEarningsAccumulatedDeficit_019d1bac-ccf8-78aa-9081-bdd51de6f010_terseLabel_en-US" xlink:label="lab_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Retained earnings (accumulated deficit)</link:label>
    <link:label id="lab_us-gaap_RetainedEarningsAccumulatedDeficit_label_en-US" xlink:label="lab_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Retained Earnings (Accumulated Deficit)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="lab_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_TransportationSectorMember_019d1bac-cc86-7069-b90f-bc5f0cf0d691_verboseLabel_en-US" xlink:label="lab_us-gaap_TransportationSectorMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Transportation</link:label>
    <link:label id="lab_us-gaap_TransportationSectorMember_label_en-US" xlink:label="lab_us-gaap_TransportationSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Transportation Sector [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransportationSectorMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransportationSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TransportationSectorMember" xlink:to="lab_us-gaap_TransportationSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee_019d1bac-cbe9-797c-ad86-402e42c55ca9_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ratio of total operating expenses to average net assets</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Expense Ratio, after Fee Waiver and Incentive Fee Deduction</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee" xlink:to="lab_us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_VariableRateComponentDomain_019e0884-2433-7131-ba9a-a2ef12070aca_terseLabel_en-US" xlink:label="lab_fsk_VariableRateComponentDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable Rate Component [Domain]</link:label>
    <link:label id="lab_fsk_VariableRateComponentDomain_label_en-US" xlink:label="lab_fsk_VariableRateComponentDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate Component [Domain]</link:label>
    <link:label id="lab_fsk_VariableRateComponentDomain_documentation_en-US" xlink:label="lab_fsk_VariableRateComponentDomain" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Variable Rate Component [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_VariableRateComponentDomain" xlink:href="fsk-20260331.xsd#fsk_VariableRateComponentDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_VariableRateComponentDomain" xlink:to="lab_fsk_VariableRateComponentDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialInstrumentAxis_019daacd-c3e1-7137-8507-97cd93c4a229_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialInstrumentAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Instrument [Axis]</link:label>
    <link:label id="lab_us-gaap_FinancialInstrumentAxis_label_en-US" xlink:label="lab_us-gaap_FinancialInstrumentAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Instrument [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialInstrumentAxis" xlink:to="lab_us-gaap_FinancialInstrumentAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StatementOfFinancialPositionAbstract_label_en-US" xlink:label="lab_us-gaap_StatementOfFinancialPositionAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementOfFinancialPositionAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract" xlink:to="lab_us-gaap_StatementOfFinancialPositionAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember_terseLabel_en-US" xlink:label="lab_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested</link:label>
    <link:label id="lab_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember_label_en-US" xlink:label="lab_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember" xlink:to="lab_ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ExecutiveCategoryAxis_terseLabel_en-US" xlink:label="lab_ecd_ExecutiveCategoryAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Executive Category:</link:label>
    <link:label id="lab_ecd_ExecutiveCategoryAxis_label_en-US" xlink:label="lab_ecd_ExecutiveCategoryAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Executive Category [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ExecutiveCategoryAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ExecutiveCategoryAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ExecutiveCategoryAxis" xlink:to="lab_ecd_ExecutiveCategoryAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ForeignExchangeForwardMember_019d1bac-ccf8-7e12-a450-799a6b190043_terseLabel_en-US" xlink:label="lab_us-gaap_ForeignExchangeForwardMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Foreign currency forward contracts</link:label>
    <link:label id="lab_us-gaap_ForeignExchangeForwardMember_label_en-US" xlink:label="lab_us-gaap_ForeignExchangeForwardMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Exchange Forward [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ForeignExchangeForwardMember" xlink:to="lab_us-gaap_ForeignExchangeForwardMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockPeriodUntilConvertible_019e1498-b224-73df-96b2-853e8185b6f1_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockPeriodUntilConvertible" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Period until covertible</link:label>
    <link:label id="lab_fsk_PreferredStockPeriodUntilConvertible_label_en-US" xlink:label="lab_fsk_PreferredStockPeriodUntilConvertible" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Period Until Convertible</link:label>
    <link:label id="lab_fsk_PreferredStockPeriodUntilConvertible_documentation_en-US" xlink:label="lab_fsk_PreferredStockPeriodUntilConvertible" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Period Until Convertible</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockPeriodUntilConvertible" xlink:href="fsk-20260331.xsd#fsk_PreferredStockPeriodUntilConvertible"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockPeriodUntilConvertible" xlink:to="lab_fsk_PreferredStockPeriodUntilConvertible" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestExpense_019d1bac-cc86-772d-a6a3-efc0839919ba_terseLabel_en-US" xlink:label="lab_us-gaap_InterestExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Interest expense</link:label>
    <link:label id="lab_us-gaap_InterestExpense_label_en-US" xlink:label="lab_us-gaap_InterestExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Expense, Operating and Nonoperating</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestExpense" xlink:to="lab_us-gaap_InterestExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019d1bac-cc86-75c7-b88e-832c8a604eee_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowings under financing arrangements</link:label>
    <link:label id="lab_us-gaap_ProceedsFromIssuanceOfLongTermDebt_label_en-US" xlink:label="lab_us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from Issuance of Long-Term Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:to="lab_us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_CurrentFiscalYearEndDate_019d1bac-cc86-71b1-82ba-fbbeec75cff6_terseLabel_en-US" xlink:label="lab_dei_CurrentFiscalYearEndDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Current Fiscal Year End Date</link:label>
    <link:label id="lab_dei_CurrentFiscalYearEndDate_label_en-US" xlink:label="lab_dei_CurrentFiscalYearEndDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Current Fiscal Year End Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_CurrentFiscalYearEndDate" xlink:to="lab_dei_CurrentFiscalYearEndDate" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_QualifyingAssetsMember_019d1bac-cc86-7206-8f87-a2d390e8fa05_terseLabel_en-US" xlink:label="lab_fsk_QualifyingAssetsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Qualifying Assets</link:label>
    <link:label id="lab_fsk_QualifyingAssetsMember_label_en-US" xlink:label="lab_fsk_QualifyingAssetsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Qualifying Assets [Member]</link:label>
    <link:label id="lab_fsk_QualifyingAssetsMember_documentation_en-US" xlink:label="lab_fsk_QualifyingAssetsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Qualifying Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_QualifyingAssetsMember" xlink:href="fsk-20260331.xsd#fsk_QualifyingAssetsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_QualifyingAssetsMember" xlink:to="lab_fsk_QualifyingAssetsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain_019d1bac-cc86-7791-bc27-70baa4918e6d_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Short-term capital gains proceeds from the sale of assets</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Short-Term Capital Gain</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution, Short-Term Capital Gain</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionShortTermCapitalGain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:to="lab_fsk_InvestmentCompanyDistributionShortTermCapitalGain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A6.875UnsecuredNotesDue2029Member_019d1bac-cbe9-7c82-9067-7f0bfc76a1dc_terseLabel_en-US" xlink:label="lab_fsk_A6.875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">6.875% Notes due 2029</link:label>
    <link:label id="lab_fsk_A6.875UnsecuredNotesDue2029Member_label_en-US" xlink:label="lab_fsk_A6.875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">6.875% Unsecured Notes due 2029 [Member]</link:label>
    <link:label id="lab_fsk_A6.875UnsecuredNotesDue2029Member_documentation_en-US" xlink:label="lab_fsk_A6.875UnsecuredNotesDue2029Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">6.875% Unsecured Notes due 2029</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A6.875UnsecuredNotesDue2029Member" xlink:href="fsk-20260331.xsd#fsk_A6.875UnsecuredNotesDue2029Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A6.875UnsecuredNotesDue2029Member" xlink:to="lab_fsk_A6.875UnsecuredNotesDue2029Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventTypeDomain_019d1bac-cc86-7de6-b807-2699c28de5b8_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Domain]</link:label>
    <link:label id="lab_us-gaap_SubsequentEventTypeDomain_label_en-US" xlink:label="lab_us-gaap_SubsequentEventTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventTypeDomain" xlink:to="lab_us-gaap_SubsequentEventTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ForeignCurrencyExchangeRateTranslation1_019d1bac-cc86-7021-9dcf-109cb4e38a8e_terseLabel_en-US" xlink:label="lab_us-gaap_ForeignCurrencyExchangeRateTranslation1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Exchange rate</link:label>
    <link:label id="lab_us-gaap_ForeignCurrencyExchangeRateTranslation1_label_en-US" xlink:label="lab_us-gaap_ForeignCurrencyExchangeRateTranslation1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Currency Exchange Rate, Translation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyExchangeRateTranslation1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyExchangeRateTranslation1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ForeignCurrencyExchangeRateTranslation1" xlink:to="lab_us-gaap_ForeignCurrencyExchangeRateTranslation1" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember_terseLabel_en-US" xlink:label="lab_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table</link:label>
    <link:label id="lab_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember_label_en-US" xlink:label="lab_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember" xlink:to="lab_ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ProfessionalFees_019d1bac-cc86-7258-9f9f-a0bc939f1a08_verboseLabel_en-US" xlink:label="lab_us-gaap_ProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Administrative services expenses</link:label>
    <link:label id="lab_us-gaap_ProfessionalFees_019d1bac-cc86-773b-abc9-bafc9507d516_terseLabel_en-US" xlink:label="lab_us-gaap_ProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Professional services</link:label>
    <link:label id="lab_us-gaap_ProfessionalFees_label_en-US" xlink:label="lab_us-gaap_ProfessionalFees" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Professional Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfessionalFees"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProfessionalFees" xlink:to="lab_us-gaap_ProfessionalFees" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StatementTable_019d1bac-cc86-7007-97a6-7883a180c80c_terseLabel_en-US" xlink:label="lab_us-gaap_StatementTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statement [Table]</link:label>
    <link:label id="lab_us-gaap_StatementTable_label_en-US" xlink:label="lab_us-gaap_StatementTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementTable" xlink:to="lab_us-gaap_StatementTable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A1.75ClassBNotesOutstandingMember_019d9f7c-35f2-7d96-beef-38d97aebd345_terseLabel_en-US" xlink:label="lab_fsk_A1.75ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">1.75% Class B Notes Outstanding</link:label>
    <link:label id="lab_fsk_A1.75ClassBNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A1.75ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">1.75% Class B Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A1.75ClassBNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A1.75ClassBNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">1.75% Class B Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A1.75ClassBNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A1.75ClassBNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A1.75ClassBNotesOutstandingMember" xlink:to="lab_fsk_A1.75ClassBNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeLiabilities_019d1bac-cc86-74a3-bb34-a6e83037f891_negatedLabel_en-US" xlink:label="lab_us-gaap_DerivativeLiabilities" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Unrealized Appreciation (Depreciation)</link:label>
    <link:label id="lab_us-gaap_DerivativeLiabilities_label_en-US" xlink:label="lab_us-gaap_DerivativeLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Liability</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeLiabilities" xlink:to="lab_us-gaap_DerivativeLiabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome_019d1bac-cc86-78f5-be23-3c7109d1e803_negatedTerseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Distributions from net investment income (in dollars per share)</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome_label_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution To Shareholder From Net Investment Income</link:label>
    <link:label id="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Distribution To Shareholder From Net Investment Income</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:to="lab_fsk_InvestmentCompanyDistributionToShareholderFromNetInvestmentIncome" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019d1bac-cbe9-70bf-9efe-931dd57a7fc6_terseLabel_en-US" xlink:label="lab_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash provided by (used in) operating activities:</link:label>
    <link:label id="lab_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_label_en-US" xlink:label="lab_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="lab_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember_019d1bac-cc86-74fe-b9d1-87b9355fb5e0_terseLabel_en-US" xlink:label="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unfunded, Senior Secured Loans&#8212;First Lien</link:label>
    <link:label id="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember_label_en-US" xlink:label="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unfunded, Senior&#160;Secured Loans, First Lien [Member]</link:label>
    <link:label id="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember_documentation_en-US" xlink:label="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unfunded, Senior&#160;Secured Loans, First Lien</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:href="fsk-20260331.xsd#fsk_UnfundedSeniorSecuredLoansFirstLienMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:to="lab_fsk_UnfundedSeniorSecuredLoansFirstLienMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019d1bac-ccf8-7e65-9874-9a5a1333da06_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash flows from financing activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember_terseLabel_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments, Excluding Value Reported in Compensation Table</link:label>
    <link:label id="lab_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember_label_en-US" xlink:label="lab_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember" xlink:to="lab_ecd_EqtyAwrdsAdjsExclgValRprtdInSummryCompstnTblMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy_019d1bac-cbe9-7d65-8fff-4015ac8d04d5_terseLabel_en-US" xlink:label="lab_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subordinated Income Incentive Fee</link:label>
    <link:label id="lab_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy_label_en-US" xlink:label="lab_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Management and Investment Advisory Fees, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy" xlink:to="lab_us-gaap_ManagementAndInvestmentAdvisoryFeesPolicy" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SeniorSecuredLoansSecondLienMember_019d1bac-ccf8-7c01-b81d-ff1ad306dee4_verboseLabel_en-US" xlink:label="lab_fsk_SeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans&#8212;Second Lien</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansSecondLienMember_019d1bac-ccf8-7e3c-a0f5-7364236cf463_terseLabel_en-US" xlink:label="lab_fsk_SeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Senior Secured Loans&#8212;Second Lien</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansSecondLienMember_label_en-US" xlink:label="lab_fsk_SeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans, Second Lien [Member]</link:label>
    <link:label id="lab_fsk_SeniorSecuredLoansSecondLienMember_documentation_en-US" xlink:label="lab_fsk_SeniorSecuredLoansSecondLienMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Senior&#160;Secured Loans, Second Lien</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SeniorSecuredLoansSecondLienMember" xlink:href="fsk-20260331.xsd#fsk_SeniorSecuredLoansSecondLienMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SeniorSecuredLoansSecondLienMember" xlink:to="lab_fsk_SeniorSecuredLoansSecondLienMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_VariableRateDomain_019d1bac-cc86-7564-941a-54f5f17db203_terseLabel_en-US" xlink:label="lab_us-gaap_VariableRateDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable Rate [Domain]</link:label>
    <link:label id="lab_us-gaap_VariableRateDomain_label_en-US" xlink:label="lab_us-gaap_VariableRateDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_VariableRateDomain" xlink:to="lab_us-gaap_VariableRateDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain_019d1bac-cbe9-78ca-a5ed-2070f52ba1fe_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Support to Nonconsolidated Legal Entity [Domain]</link:label>
    <link:label id="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain_label_en-US" xlink:label="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Support to Nonconsolidated Legal Entity [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain" xlink:to="lab_us-gaap_FinancialSupportToNonconsolidatedLegalEntityDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest_019d1bac-cc86-7a53-8c30-135da168c099_terseLabel_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Gross investment income attributable to paid-in-kind interest</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest_label_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable To Paid-In-Kind Interest</link:label>
    <link:label id="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest_documentation_en-US" xlink:label="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Percentage Attributable To Paid-In-Kind Interest</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:href="fsk-20260331.xsd#fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:to="lab_fsk_GrossInvestmentIncomePercentageAttributableToPaidInKindInterest" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_019d1bac-cbe9-7fd6-9689-32c00d97672d_terseLabel_en-US" xlink:label="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Principal Business and Organization</link:label>
    <link:label id="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" xlink:to="lab_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_019d1bac-cc86-713f-a335-c3df981f4529_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Reconciliation Fair Value, Assets</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInManagementFeePayable_019d1bac-cc86-7996-8d13-be4233ef6c82_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInManagementFeePayable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in management fees payable</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInManagementFeePayable_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInManagementFeePayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Management Fee Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInManagementFeePayable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInManagementFeePayable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInManagementFeePayable" xlink:to="lab_us-gaap_IncreaseDecreaseInManagementFeePayable" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_AllAdjToCompMember_terseLabel_en-US" xlink:label="lab_ecd_AllAdjToCompMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">All Adjustments to Compensation</link:label>
    <link:label id="lab_ecd_AllAdjToCompMember_label_en-US" xlink:label="lab_ecd_AllAdjToCompMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">All Adjustments to Compensation [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllAdjToCompMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllAdjToCompMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="lab_ecd_AllAdjToCompMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CostApproachValuationTechniqueMember_019d1bac-cc86-7a6a-9ca5-fa06b7783cc2_verboseLabel_en-US" xlink:label="lab_us-gaap_CostApproachValuationTechniqueMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Cost</link:label>
    <link:label id="lab_us-gaap_CostApproachValuationTechniqueMember_label_en-US" xlink:label="lab_us-gaap_CostApproachValuationTechniqueMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation, Cost Approach [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostApproachValuationTechniqueMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostApproachValuationTechniqueMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CostApproachValuationTechniqueMember" xlink:to="lab_us-gaap_CostApproachValuationTechniqueMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember_019d6645-6e38-7ec4-9753-500937fbc34c_terseLabel_en-US" xlink:label="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrealized appreciation on foreign currency forward contracts</link:label>
    <link:label id="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember_label_en-US" xlink:label="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrealized Appreciation On Foreign Currency Forward Contracts [Member]</link:label>
    <link:label id="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember_documentation_en-US" xlink:label="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unrealized Appreciation On Foreign Currency Forward Contracts</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:href="fsk-20260331.xsd#fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:to="lab_fsk_UnrealizedAppreciationOnForeignCurrencyForwardContractsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_AmendmentFlag_019d1bac-cc86-70ac-96b8-dca733072c6e_terseLabel_en-US" xlink:label="lab_dei_AmendmentFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Amendment Flag</link:label>
    <link:label id="lab_dei_AmendmentFlag_label_en-US" xlink:label="lab_dei_AmendmentFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Amendment Flag</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_AmendmentFlag" xlink:to="lab_dei_AmendmentFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EnergySectorMember_019d1bac-cc86-7a46-954d-45ce2aba42eb_terseLabel_en-US" xlink:label="lab_us-gaap_EnergySectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Energy</link:label>
    <link:label id="lab_us-gaap_EnergySectorMember_label_en-US" xlink:label="lab_us-gaap_EnergySectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Energy Sector [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnergySectorMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EnergySectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EnergySectorMember" xlink:to="lab_us-gaap_EnergySectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FinancialGuaranteeMember_019e14d1-5fb0-7690-9037-bb5177ff8e0e_terseLabel_en-US" xlink:label="lab_us-gaap_FinancialGuaranteeMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Financial Guarantee</link:label>
    <link:label id="lab_us-gaap_FinancialGuaranteeMember_label_en-US" xlink:label="lab_us-gaap_FinancialGuaranteeMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Financial Guarantee [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialGuaranteeMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FinancialGuaranteeMember" xlink:to="lab_us-gaap_FinancialGuaranteeMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DarbyCreekCreditFacilityMember_019d1bac-cc86-7950-a401-7ab87e93dd93_terseLabel_en-US" xlink:label="lab_fsk_DarbyCreekCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Darby Creek Credit Facility</link:label>
    <link:label id="lab_fsk_DarbyCreekCreditFacilityMember_label_en-US" xlink:label="lab_fsk_DarbyCreekCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Darby Creek Credit Facility [Member]</link:label>
    <link:label id="lab_fsk_DarbyCreekCreditFacilityMember_documentation_en-US" xlink:label="lab_fsk_DarbyCreekCreditFacilityMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Darby Creek Credit Facility</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DarbyCreekCreditFacilityMember" xlink:href="fsk-20260331.xsd#fsk_DarbyCreekCreditFacilityMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DarbyCreekCreditFacilityMember" xlink:to="lab_fsk_DarbyCreekCreditFacilityMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherCommitmentsTable_019d1bac-cc86-7e6f-b24c-9b7958abeae0_terseLabel_en-US" xlink:label="lab_us-gaap_OtherCommitmentsTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Commitments [Table]</link:label>
    <link:label id="lab_us-gaap_OtherCommitmentsTable_label_en-US" xlink:label="lab_us-gaap_OtherCommitmentsTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Commitments [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherCommitmentsTable" xlink:to="lab_us-gaap_OtherCommitmentsTable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DeferredTaxAssetsInvestments_019d1bac-cc86-7f5f-ae38-a3ab0a61d843_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredTaxAssetsInvestments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred tax asset</link:label>
    <link:label id="lab_us-gaap_DeferredTaxAssetsInvestments_label_en-US" xlink:label="lab_us-gaap_DeferredTaxAssetsInvestments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Tax Assets, Investments</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsInvestments" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsInvestments"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DeferredTaxAssetsInvestments" xlink:to="lab_us-gaap_DeferredTaxAssetsInvestments" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet_019d1bac-cc86-731a-bd33-822671df454e_terseLabel_en-US" xlink:label="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred financing costs</link:label>
    <link:label id="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet_label_en-US" xlink:label="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Issuance Costs, Line of Credit Arrangements, Net</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:to="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TrdArrTerminationDate_terseLabel_en-US" xlink:label="lab_ecd_TrdArrTerminationDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Termination Date</link:label>
    <link:label id="lab_ecd_TrdArrTerminationDate_label_en-US" xlink:label="lab_ecd_TrdArrTerminationDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement Termination Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TrdArrTerminationDate" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TrdArrTerminationDate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TrdArrTerminationDate" xlink:to="lab_ecd_TrdArrTerminationDate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInFinancingActivities_019d1bac-cc86-7352-b7c3-e2b06ccfc7ab_totalLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash provided by (used in) financing activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInFinancingActivities_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="lab_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_InsiderTrdPoliciesProcAdoptedFlag_terseLabel_en-US" xlink:label="lab_ecd_InsiderTrdPoliciesProcAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Insider Trading Policies and Procedures Adopted</link:label>
    <link:label id="lab_ecd_InsiderTrdPoliciesProcAdoptedFlag_label_en-US" xlink:label="lab_ecd_InsiderTrdPoliciesProcAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Insider Trading Policies and Procedures Adopted [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_InsiderTrdPoliciesProcAdoptedFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_InsiderTrdPoliciesProcAdoptedFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_InsiderTrdPoliciesProcAdoptedFlag" xlink:to="lab_ecd_InsiderTrdPoliciesProcAdoptedFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_MeasureAxis_terseLabel_en-US" xlink:label="lab_ecd_MeasureAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Measure:</link:label>
    <link:label id="lab_ecd_MeasureAxis_label_en-US" xlink:label="lab_ecd_MeasureAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Measure [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_MeasureAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_MeasureAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_MeasureAxis" xlink:to="lab_ecd_MeasureAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionGainLossRealized_019d1bac-cc86-7f84-857c-50b6f157f6be_terseLabel_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss) on foreign currency</link:label>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionGainLossRealized_label_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Realized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:to="lab_us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_ScheduleOfDistributionLineItems_019d1bac-cc86-75d1-8682-4581cbcab9b5_terseLabel_en-US" xlink:label="lab_fsk_ScheduleOfDistributionLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Distributions [Line Items]</link:label>
    <link:label id="lab_fsk_ScheduleOfDistributionLineItems_label_en-US" xlink:label="lab_fsk_ScheduleOfDistributionLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Distribution [Line Items]</link:label>
    <link:label id="lab_fsk_ScheduleOfDistributionLineItems_documentation_en-US" xlink:label="lab_fsk_ScheduleOfDistributionLineItems" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule of Distribution [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_ScheduleOfDistributionLineItems" xlink:href="fsk-20260331.xsd#fsk_ScheduleOfDistributionLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_ScheduleOfDistributionLineItems" xlink:to="lab_fsk_ScheduleOfDistributionLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod_019e149d-f47d-7c1d-9f24-b685cef741bd_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Period until shares are eligible to redeem at redemption price</link:label>
    <link:label id="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod_label_en-US" xlink:label="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Shares Eligible To Redeem At Redemption Price, Period</link:label>
    <link:label id="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod_documentation_en-US" xlink:label="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Shares Eligible To Redeem At Redemption Price, Period</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:href="fsk-20260331.xsd#fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:to="lab_fsk_PreferredStockSharesEligibleToRedeemAtRedemptionPricePeriod" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare_019d1bac-cbe9-712b-98dd-ed136f492060_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Distributions from net realized gain on investments (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Realized Gain (Loss) on Investment, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare" xlink:to="lab_us-gaap_InvestmentCompanyRealizedGainLossOnInvestmentPerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AssetsNet_019d1bac-cbe9-73a4-847e-d1c4b1675f76_totalLabel_en-US" xlink:label="lab_us-gaap_AssetsNet" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net Assets</link:label>
    <link:label id="lab_us-gaap_AssetsNet_label_en-US" xlink:label="lab_us-gaap_AssetsNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Assets</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AssetsNet" xlink:to="lab_us-gaap_AssetsNet" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ValuationTechniqueAxis_019d1bac-cc86-79d6-9919-070529de22b3_terseLabel_en-US" xlink:label="lab_us-gaap_ValuationTechniqueAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Valuation Approach and Technique [Axis]</link:label>
    <link:label id="lab_us-gaap_ValuationTechniqueAxis_label_en-US" xlink:label="lab_us-gaap_ValuationTechniqueAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation Approach and Technique [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ValuationTechniqueAxis" xlink:to="lab_us-gaap_ValuationTechniqueAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember_019d1bac-cc86-797f-925f-7d135c6e2f23_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income Below Catch-Up Threshold</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income Below Catch-Up Threshold [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Pre-Incentive Fee Net Investment Income Below Catch-Up Threshold</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock_019d1bac-cbe9-755e-88fe-f2e2419d1849_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Fair Value Hierarchy Investments</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Assets Measured on Recurring Basis [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019d1bac-cc86-72a0-8f9f-b6e2a7d467ce_terseLabel_en-US" xlink:label="lab_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted average shares outstanding - basic (in shares)</link:label>
    <link:label id="lab_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_label_en-US" xlink:label="lab_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted Average Number of Shares Outstanding, Basic</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:to="lab_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsRollForward_019d1bac-cbe9-73bd-a65f-13210d9a56a0_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsRollForward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Highlights [Roll Forward]</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyFinancialHighlightsRollForward_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyFinancialHighlightsRollForward" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Financial Highlights [Roll Forward]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyFinancialHighlightsRollForward" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyFinancialHighlightsRollForward"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyFinancialHighlightsRollForward" xlink:to="lab_us-gaap_InvestmentCompanyFinancialHighlightsRollForward" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DividendAndInterestReceivable_019d1bac-cc86-784f-966c-7afb8e87d343_terseLabel_en-US" xlink:label="lab_us-gaap_DividendAndInterestReceivable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income receivable</link:label>
    <link:label id="lab_us-gaap_DividendAndInterestReceivable_label_en-US" xlink:label="lab_us-gaap_DividendAndInterestReceivable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Dividend and Interest Receivable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendAndInterestReceivable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendAndInterestReceivable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DividendAndInterestReceivable" xlink:to="lab_us-gaap_DividendAndInterestReceivable" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A205CommitmentsOutstandingMember_019d1bac-cbe9-7dbf-8f56-8e47b60a4ece_terseLabel_en-US" xlink:label="lab_fsk_A205CommitmentsOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2.05% Commitments Outstanding</link:label>
    <link:label id="lab_fsk_A205CommitmentsOutstandingMember_label_en-US" xlink:label="lab_fsk_A205CommitmentsOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">2.05% Commitments Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A205CommitmentsOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A205CommitmentsOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">2.05% Commitments Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A205CommitmentsOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A205CommitmentsOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A205CommitmentsOutstandingMember" xlink:to="lab_fsk_A205CommitmentsOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_RelatedPartyTransactionDomain_019d1bac-cc86-7b53-b327-68ef3717c79d_terseLabel_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Domain]</link:label>
    <link:label id="lab_us-gaap_RelatedPartyTransactionDomain_label_en-US" xlink:label="lab_us-gaap_RelatedPartyTransactionDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transaction [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain" xlink:to="lab_us-gaap_RelatedPartyTransactionDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventsAbstract_label_en-US" xlink:label="lab_us-gaap_SubsequentEventsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Events [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventsAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventsAbstract" xlink:to="lab_us-gaap_SubsequentEventsAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SegmentReportingAbstract_label_en-US" xlink:label="lab_us-gaap_SegmentReportingAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Segment Reporting [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SegmentReportingAbstract" xlink:to="lab_us-gaap_SegmentReportingAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PvpTableTextBlock_terseLabel_en-US" xlink:label="lab_ecd_PvpTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pay vs Performance Disclosure, Table</link:label>
    <link:label id="lab_ecd_PvpTableTextBlock_label_en-US" xlink:label="lab_ecd_PvpTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pay vs Performance [Table Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PvpTableTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PvpTableTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PvpTableTextBlock" xlink:to="lab_ecd_PvpTableTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_RevolvingCommitmentOutstanding_019d1bac-cc86-75a4-9ead-e84211b9c1e8_terseLabel_en-US" xlink:label="lab_fsk_RevolvingCommitmentOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revolving commitment outstanding</link:label>
    <link:label id="lab_fsk_RevolvingCommitmentOutstanding_label_en-US" xlink:label="lab_fsk_RevolvingCommitmentOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revolving Commitment Outstanding</link:label>
    <link:label id="lab_fsk_RevolvingCommitmentOutstanding_documentation_en-US" xlink:label="lab_fsk_RevolvingCommitmentOutstanding" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Revolving Commitment Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_RevolvingCommitmentOutstanding" xlink:href="fsk-20260331.xsd#fsk_RevolvingCommitmentOutstanding"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_RevolvingCommitmentOutstanding" xlink:to="lab_fsk_RevolvingCommitmentOutstanding" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtDisclosureAbstract_label_en-US" xlink:label="lab_us-gaap_DebtDisclosureAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Disclosure [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtDisclosureAbstract" xlink:to="lab_us-gaap_DebtDisclosureAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt_terseLabel_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Violation of Home Country Law, Amount</link:label>
    <link:label id="lab_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt_label_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Violation of Home Country Law, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt" xlink:to="lab_ecd_ForgoneRecoveryDueToViolationOfHomeCountryLawAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement_019d1bac-cc86-77ce-a0c5-d694333c55a3_totalLabel_en-US" xlink:label="lab_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total</link:label>
    <link:label id="lab_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement_label_en-US" xlink:label="lab_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Subject to Master Netting Arrangement, after Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement" xlink:to="lab_us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentIncomeInvestmentExpense_019d1bac-ccf8-720a-afad-7c2290c05eb0_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentIncomeInvestmentExpense" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total operating expenses</link:label>
    <link:label id="lab_us-gaap_InvestmentIncomeInvestmentExpense_label_en-US" xlink:label="lab_us-gaap_InvestmentIncomeInvestmentExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Income, Investment Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentIncomeInvestmentExpense" xlink:to="lab_us-gaap_InvestmentIncomeInvestmentExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityTaxIdentificationNumber_019d1bac-ccf8-7f86-a732-a2bdcd8ef30d_terseLabel_en-US" xlink:label="lab_dei_EntityTaxIdentificationNumber" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Tax Identification Number</link:label>
    <link:label id="lab_dei_EntityTaxIdentificationNumber_label_en-US" xlink:label="lab_dei_EntityTaxIdentificationNumber" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Tax Identification Number</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityTaxIdentificationNumber" xlink:to="lab_dei_EntityTaxIdentificationNumber" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ScenarioUnspecifiedDomain_019e14c2-af5b-7491-9ada-a6dd96ac6391_terseLabel_en-US" xlink:label="lab_srt_ScenarioUnspecifiedDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Scenario [Domain]</link:label>
    <link:label id="lab_srt_ScenarioUnspecifiedDomain_label_en-US" xlink:label="lab_srt_ScenarioUnspecifiedDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ScenarioUnspecifiedDomain" xlink:to="lab_srt_ScenarioUnspecifiedDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ValuationTechniqueDiscountedCashFlowMember_019d1bac-cc86-75be-ac4c-f275514f8b35_terseLabel_en-US" xlink:label="lab_us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Discounted Cash Flow</link:label>
    <link:label id="lab_us-gaap_ValuationTechniqueDiscountedCashFlowMember_label_en-US" xlink:label="lab_us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Valuation Technique, Discounted Cash Flow [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:to="lab_us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions_019d1bac-cc86-7da7-83aa-dcf8c6c81ebe_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Return of capital</link:label>
    <link:label id="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions_label_en-US" xlink:label="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Tax Return of Capital Distribution, Percent Of Total Distributions</link:label>
    <link:label id="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Tax Return of Capital Distribution, Percent Of Total Distributions</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:to="lab_fsk_InvestmentCompanyTaxReturnOfCapitalDistributionPercentOfTotalDistributions" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental_019d1bac-cc86-72cc-a19f-48105aceeac1_terseLabel_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Supplemental (in dollars per share)</link:label>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental_label_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Dividends, Per Share, Declared, Supplemental</link:label>
    <link:label id="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental_documentation_en-US" xlink:label="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Common Stock, Dividends, Per Share, Declared, Supplemental</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:href="fsk-20260331.xsd#fsk_CommonStockDividendsPerShareDeclaredSupplemental"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:to="lab_fsk_CommonStockDividendsPerShareDeclaredSupplemental" xlink:type="arc" order="1"/>
    <link:label id="lab_currency_GBP_019d1bac-cc86-7930-a60b-01d96206d70b_terseLabel_en-US" xlink:label="lab_currency_GBP" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">GBP</link:label>
    <link:label id="lab_currency_GBP_label_en-US" xlink:label="lab_currency_GBP" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">United Kingdom, Pounds</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_currency_GBP" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_GBP"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_currency_GBP" xlink:to="lab_currency_GBP" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CommercialAndProfessionalServicesSectorMember_019d1bac-ccf8-7655-ba27-76186eedeeac_terseLabel_en-US" xlink:label="lab_fsk_CommercialAndProfessionalServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Commercial &amp; Professional Services</link:label>
    <link:label id="lab_fsk_CommercialAndProfessionalServicesSectorMember_label_en-US" xlink:label="lab_fsk_CommercialAndProfessionalServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commercial And Professional Services Sector [Member]</link:label>
    <link:label id="lab_fsk_CommercialAndProfessionalServicesSectorMember_documentation_en-US" xlink:label="lab_fsk_CommercialAndProfessionalServicesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Commercial And Professional Services Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CommercialAndProfessionalServicesSectorMember" xlink:href="fsk-20260331.xsd#fsk_CommercialAndProfessionalServicesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CommercialAndProfessionalServicesSectorMember" xlink:to="lab_fsk_CommercialAndProfessionalServicesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent_019d1bac-cc86-7cba-98c5-198b4f837247_terseLabel_en-US" xlink:label="lab_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Administrative services expense payable</link:label>
    <link:label id="lab_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent_label_en-US" xlink:label="lab_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accrued Professional Fees</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent" xlink:to="lab_us-gaap_AccruedProfessionalFeesCurrentAndNoncurrent" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt_terseLabel_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Expense of Enforcement, Amount</link:label>
    <link:label id="lab_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt_label_en-US" xlink:label="lab_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forgone Recovery due to Expense of Enforcement, Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt" xlink:to="lab_ecd_ForgoneRecoveryDueToExpenseOfEnforcementAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember_019d1bac-cc86-7d59-9bec-4f14813a18b8_terseLabel_en-US" xlink:label="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">SCRS</link:label>
    <link:label id="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember_label_en-US" xlink:label="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">South Carolina Retirement Systems Group Trust [Member]</link:label>
    <link:label id="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember_documentation_en-US" xlink:label="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">South Carolina Retirement Systems Group Trust [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:href="fsk-20260331.xsd#fsk_SouthCarolinaRetirementSystemsGroupTrustMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:to="lab_fsk_SouthCarolinaRetirementSystemsGroupTrustMember" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_ConsolidatedEntitiesAxis_019d1bac-cc86-7823-a2f5-eabeec124b0d_terseLabel_en-US" xlink:label="lab_srt_ConsolidatedEntitiesAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Consolidated Entities [Axis]</link:label>
    <link:label id="lab_srt_ConsolidatedEntitiesAxis_label_en-US" xlink:label="lab_srt_ConsolidatedEntitiesAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consolidated Entities [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_ConsolidatedEntitiesAxis" xlink:to="lab_srt_ConsolidatedEntitiesAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockParOrStatedValuePerShare_019d1bac-cc86-7450-8ba0-c5661c868c74_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common stock, par value (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_CommonStockParOrStatedValuePerShare_label_en-US" xlink:label="lab_us-gaap_CommonStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Par or Stated Value Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="lab_us-gaap_CommonStockParOrStatedValuePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CommonStockSharesIssued_019d1bac-cc86-7347-9d5e-b7e1f149b3bc_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockSharesIssued" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common stock, shares issued (in shares)</link:label>
    <link:label id="lab_us-gaap_CommonStockSharesIssued_label_en-US" xlink:label="lab_us-gaap_CommonStockSharesIssued" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock, Shares, Issued</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockSharesIssued" xlink:to="lab_us-gaap_CommonStockSharesIssued" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember_019d1bac-cc86-7bfd-a6b6-c23fcdc8db7f_terseLabel_en-US" xlink:label="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pharmaceuticals, Biotechnology &amp; Life Sciences</link:label>
    <link:label id="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember_label_en-US" xlink:label="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pharmaceuticals, Biotechnology &amp; Life Sciences Sector [Member]</link:label>
    <link:label id="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember_documentation_en-US" xlink:label="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Pharmaceuticals, Biotechnology &amp; Life Sciences Sector</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:href="fsk-20260331.xsd#fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:to="lab_fsk_PharmaceuticalsBiotechnologyLifeSciencesSectorMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets_019d1bac-cc86-725f-85d6-16b9c09e380e_terseLabel_en-US" xlink:label="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Liabilities in excess of other assets percentage</link:label>
    <link:label id="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets_label_en-US" xlink:label="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Noninvestment Asset Less Noninvestment Liability, Percent of Net Asset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets" xlink:to="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilitiesPercentOfNetAssets" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AvenueOnePropCoMember_019e0292-f915-7e3d-b467-46fc9564ba9f_terseLabel_en-US" xlink:label="lab_fsk_AvenueOnePropCoMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Avenue One PropCo</link:label>
    <link:label id="lab_fsk_AvenueOnePropCoMember_label_en-US" xlink:label="lab_fsk_AvenueOnePropCoMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Avenue One PropCo [Member]</link:label>
    <link:label id="lab_fsk_AvenueOnePropCoMember_documentation_en-US" xlink:label="lab_fsk_AvenueOnePropCoMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Avenue One PropCo</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AvenueOnePropCoMember" xlink:href="fsk-20260331.xsd#fsk_AvenueOnePropCoMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AvenueOnePropCoMember" xlink:to="lab_fsk_AvenueOnePropCoMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities_019d1bac-cc86-7140-b3e3-f800435b9421_verboseLabel_en-US" xlink:label="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Liabilities in excess of other assets</link:label>
    <link:label id="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities_label_en-US" xlink:label="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Noninvestment Assets Less Noninvestment Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities" xlink:to="lab_us-gaap_NonInvestmentAssetsLessNonInvestmentLiabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_UseOfEstimates_019d1bac-ccf8-7f7f-8ba9-a9c81cea4fe8_terseLabel_en-US" xlink:label="lab_us-gaap_UseOfEstimates" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Use of Estimates</link:label>
    <link:label id="lab_us-gaap_UseOfEstimates_label_en-US" xlink:label="lab_us-gaap_UseOfEstimates" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Use of Estimates, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UseOfEstimates" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UseOfEstimates"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_UseOfEstimates" xlink:to="lab_us-gaap_UseOfEstimates" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_GuaranteeObligationsByNatureAxis_019e14d1-416b-77bb-a3a1-aa8dcb3c013a_terseLabel_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsByNatureAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Guarantor Obligations, Nature [Axis]</link:label>
    <link:label id="lab_us-gaap_GuaranteeObligationsByNatureAxis_label_en-US" xlink:label="lab_us-gaap_GuaranteeObligationsByNatureAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Guarantor Obligations, Nature [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis" xlink:to="lab_us-gaap_GuaranteeObligationsByNatureAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember_019d1bac-cc86-7324-9249-b3894f87240f_terseLabel_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Hurdle Rate</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember_label_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Hurdle Rate [Member]</link:label>
    <link:label id="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember_documentation_en-US" xlink:label="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Advisory Agreement - Incentive Rate, Annualized Hurdle Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:href="fsk-20260331.xsd#fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:to="lab_fsk_InvestmentAdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TradingArrAxis_terseLabel_en-US" xlink:label="lab_ecd_TradingArrAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Trading Arrangement:</link:label>
    <link:label id="lab_ecd_TradingArrAxis_label_en-US" xlink:label="lab_ecd_TradingArrAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Arrangement [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TradingArrAxis" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TradingArrAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TradingArrAxis" xlink:to="lab_ecd_TradingArrAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_TotalShareholderRtnAmt_terseLabel_en-US" xlink:label="lab_ecd_TotalShareholderRtnAmt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total Shareholder Return Amount</link:label>
    <link:label id="lab_ecd_TotalShareholderRtnAmt_label_en-US" xlink:label="lab_ecd_TotalShareholderRtnAmt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Total Shareholder Return Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_TotalShareholderRtnAmt" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_TotalShareholderRtnAmt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_TotalShareholderRtnAmt" xlink:to="lab_ecd_TotalShareholderRtnAmt" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_AdministrativeServicesExpenses_019d1bac-cc86-7a06-9fcf-f9813d29fdbc_terseLabel_en-US" xlink:label="lab_fsk_AdministrativeServicesExpenses" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Administrative services</link:label>
    <link:label id="lab_fsk_AdministrativeServicesExpenses_label_en-US" xlink:label="lab_fsk_AdministrativeServicesExpenses" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Administrative Services Expenses</link:label>
    <link:label id="lab_fsk_AdministrativeServicesExpenses_documentation_en-US" xlink:label="lab_fsk_AdministrativeServicesExpenses" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Administrative Services Expenses</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_AdministrativeServicesExpenses" xlink:href="fsk-20260331.xsd#fsk_AdministrativeServicesExpenses"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_AdministrativeServicesExpenses" xlink:to="lab_fsk_AdministrativeServicesExpenses" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock_019d1bac-cc86-7439-8b59-75a59946df33_terseLabel_en-US" xlink:label="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Capital Gains Incentive Fee</link:label>
    <link:label id="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock_label_en-US" xlink:label="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Capital Gains Incentive Fee [Policy Text Block]</link:label>
    <link:label id="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock_documentation_en-US" xlink:label="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Capital Gains Incentive Fee</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:href="fsk-20260331.xsd#fsk_CapitalGainsIncentiveFeePolicyTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:to="lab_fsk_CapitalGainsIncentiveFeePolicyTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventsTextBlock_019d1bac-cc86-7b05-94d9-16815c7140d7_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventsTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Events</link:label>
    <link:label id="lab_us-gaap_SubsequentEventsTextBlock_label_en-US" xlink:label="lab_us-gaap_SubsequentEventsTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Events [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventsTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventsTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventsTextBlock" xlink:to="lab_us-gaap_SubsequentEventsTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeAssetFairValueGrossLiability_019d1bac-cc86-7bb4-af54-276e32022aeb_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Derivatives Available for Offset</link:label>
    <link:label id="lab_us-gaap_DerivativeAssetFairValueGrossLiability_019d1bac-cc86-751c-9226-bc2a8c92a53e_negatedLabel_en-US" xlink:label="lab_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Derivatives Available for Offset</link:label>
    <link:label id="lab_us-gaap_DerivativeAssetFairValueGrossLiability_label_en-US" xlink:label="lab_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative Asset, Subject to Master Netting Arrangement, Liability Offset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossLiability"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:to="lab_us-gaap_DerivativeAssetFairValueGrossLiability" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_InsiderTradingArrLineItems_label_en-US" xlink:label="lab_ecd_InsiderTradingArrLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Insider Trading Arrangements [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_InsiderTradingArrLineItems" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_InsiderTradingArrLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_InsiderTradingArrLineItems" xlink:to="lab_ecd_InsiderTradingArrLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation_019d1bac-cc86-7c6f-bdba-25482ead19c9_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Change in Unrealized Appreciation/(Depreciation)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Distributable Earnings (Loss), Accumulated Appreciation (Depreciation)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation" xlink:to="lab_us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciationDepreciation" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_SecurityExchangeName_019d1bac-cc86-7997-b1e5-42b4cb64d5d9_terseLabel_en-US" xlink:label="lab_dei_SecurityExchangeName" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Security Exchange Name</link:label>
    <link:label id="lab_dei_SecurityExchangeName_label_en-US" xlink:label="lab_dei_SecurityExchangeName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Security Exchange Name</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_SecurityExchangeName" xlink:to="lab_dei_SecurityExchangeName" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersDomain_019d1bac-cbe9-7f24-a5c9-d5b03d390945_terseLabel_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders [Domain]</link:label>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersDomain_label_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders [Domain]</link:label>
    <link:label id="lab_fsk_BorrowingsTypeOfLendersDomain_documentation_en-US" xlink:label="lab_fsk_BorrowingsTypeOfLendersDomain" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Borrowings, Type Of Lenders [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_BorrowingsTypeOfLendersDomain" xlink:href="fsk-20260331.xsd#fsk_BorrowingsTypeOfLendersDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_BorrowingsTypeOfLendersDomain" xlink:to="lab_fsk_BorrowingsTypeOfLendersDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EquitySecuritiesMember_019d1bac-ccf8-7082-8453-67fe2ef24cf8_terseLabel_en-US" xlink:label="lab_us-gaap_EquitySecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity/Other</link:label>
    <link:label id="lab_us-gaap_EquitySecuritiesMember_label_en-US" xlink:label="lab_us-gaap_EquitySecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Securities [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EquitySecuritiesMember" xlink:to="lab_us-gaap_EquitySecuritiesMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_A2.10ClassCNotesOutstandingMember_019d9f67-34be-7a49-9079-5370a0866464_terseLabel_en-US" xlink:label="lab_fsk_A2.10ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2.10% Class C Notes Outstanding</link:label>
    <link:label id="lab_fsk_A2.10ClassCNotesOutstandingMember_label_en-US" xlink:label="lab_fsk_A2.10ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">2.10% Class C Notes Outstanding [Member]</link:label>
    <link:label id="lab_fsk_A2.10ClassCNotesOutstandingMember_documentation_en-US" xlink:label="lab_fsk_A2.10ClassCNotesOutstandingMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">2.10% Class C Notes Outstanding</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_A2.10ClassCNotesOutstandingMember" xlink:href="fsk-20260331.xsd#fsk_A2.10ClassCNotesOutstandingMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_A2.10ClassCNotesOutstandingMember" xlink:to="lab_fsk_A2.10ClassCNotesOutstandingMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_Liabilities_019d1bac-cc86-7ce3-bc43-d1b0aec328ed_totalLabel_en-US" xlink:label="lab_us-gaap_Liabilities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total liabilities</link:label>
    <link:label id="lab_us-gaap_Liabilities_label_en-US" xlink:label="lab_us-gaap_Liabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_Liabilities" xlink:to="lab_us-gaap_Liabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_CurrencyAxis_019d1bac-cc86-7109-a2dc-9e4501a88933_terseLabel_en-US" xlink:label="lab_srt_CurrencyAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Currency [Axis]</link:label>
    <link:label id="lab_srt_CurrencyAxis_label_en-US" xlink:label="lab_srt_CurrencyAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Currency [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_CurrencyAxis" xlink:to="lab_srt_CurrencyAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAxis_019dfefd-24af-7c9f-a15e-eff109361f86_terseLabel_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents [Axis]</link:label>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAxis_label_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis" xlink:to="lab_us-gaap_CashAndCashEquivalentsAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019d1bac-cc86-7f4f-a047-a9ef127e40ff_verboseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Amount outstanding</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019d1bac-cc86-7ec8-bad2-08317ce9e86a_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maximum borrowing capacity</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:to="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember_019d1bac-ccf8-7299-a137-e8effbd3af65_terseLabel_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss)</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember_label_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Realized Gain (Loss) [Member]</link:label>
    <link:label id="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember_documentation_en-US" xlink:label="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt and Equity Securities, Realized Gain (Loss)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:href="fsk-20260331.xsd#fsk_DebtAndEquitySecuritiesRealizedGainLossMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:to="lab_fsk_DebtAndEquitySecuritiesRealizedGainLossMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_O2026M2AggregateDividendsMember_019d1bac-cc86-7f6b-bd67-1a9fb20d9919_terseLabel_en-US" xlink:label="lab_fsk_O2026M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">O 2026 M2 Aggregate Dividends</link:label>
    <link:label id="lab_fsk_O2026M2AggregateDividendsMember_label_en-US" xlink:label="lab_fsk_O2026M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">O 2026 M2 Aggregate Dividends [Member]</link:label>
    <link:label id="lab_fsk_O2026M2AggregateDividendsMember_documentation_en-US" xlink:label="lab_fsk_O2026M2AggregateDividendsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">O 2026 M2 Aggregate Dividends</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_O2026M2AggregateDividendsMember" xlink:href="fsk-20260331.xsd#fsk_O2026M2AggregateDividendsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_O2026M2AggregateDividendsMember" xlink:to="lab_fsk_O2026M2AggregateDividendsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_019d1bac-cc86-769a-8f1c-8ee810da4a1b_terseLabel_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock repurchased and distributed (in shares)</link:label>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_label_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Dividend Reinvestment Plan</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:to="lab_us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan_019e1488-af7a-7804-b288-1854472852d7_terseLabel_en-US" xlink:label="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of business days after tender off to enter trading plan</link:label>
    <link:label id="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan_label_en-US" xlink:label="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number Of Business Days After Sale Of Stock To Enter Trading Plan</link:label>
    <link:label id="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan_documentation_en-US" xlink:label="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Number Of Business Days After Sale Of Stock To Enter Trading Plan</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:href="fsk-20260331.xsd#fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:to="lab_fsk_NumberOfBusinessDaysAfterSaleOfStockToEnterTradingPlan" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_PnsnAdjsPrrSvcCstMember_terseLabel_en-US" xlink:label="lab_ecd_PnsnAdjsPrrSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Pension Adjustments Prior Service Cost</link:label>
    <link:label id="lab_ecd_PnsnAdjsPrrSvcCstMember_label_en-US" xlink:label="lab_ecd_PnsnAdjsPrrSvcCstMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Pension Adjustments Prior Service Cost [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_PnsnAdjsPrrSvcCstMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PnsnAdjsPrrSvcCstMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_PnsnAdjsPrrSvcCstMember" xlink:to="lab_ecd_PnsnAdjsPrrSvcCstMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InvestmentCompanyMarketValuePerShare_019d1bac-cc86-7611-8854-bae2952f7310_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentCompanyMarketValuePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Per share market value, end of period (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_InvestmentCompanyMarketValuePerShare_label_en-US" xlink:label="lab_us-gaap_InvestmentCompanyMarketValuePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Market Value, Per Share</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentCompanyMarketValuePerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyMarketValuePerShare"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentCompanyMarketValuePerShare" xlink:to="lab_us-gaap_InvestmentCompanyMarketValuePerShare" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DerivativeVariableInterestRate_019d1bac-cbe9-786a-8e0b-a7a27b8958e7_terseLabel_en-US" xlink:label="lab_us-gaap_DerivativeVariableInterestRate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Floating interest rate (as percent)</link:label>
    <link:label id="lab_us-gaap_DerivativeVariableInterestRate_label_en-US" xlink:label="lab_us-gaap_DerivativeVariableInterestRate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Derivative, Variable Interest Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeVariableInterestRate" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeVariableInterestRate"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DerivativeVariableInterestRate" xlink:to="lab_us-gaap_DerivativeVariableInterestRate" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OperatingExpensesAbstract_019d1bac-cc86-7fd6-bf0f-b8ca9fb800f9_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingExpensesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating expenses</link:label>
    <link:label id="lab_us-gaap_OperatingExpensesAbstract_019d1bac-cc86-72ad-badd-8dd4902af70e_verboseLabel_en-US" xlink:label="lab_us-gaap_OperatingExpensesAbstract" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Expenses</link:label>
    <link:label id="lab_us-gaap_OperatingExpensesAbstract_label_en-US" xlink:label="lab_us-gaap_OperatingExpensesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Expenses [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingExpensesAbstract" xlink:to="lab_us-gaap_OperatingExpensesAbstract" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_MtrlTermsOfTrdArrTextBlock_terseLabel_en-US" xlink:label="lab_ecd_MtrlTermsOfTrdArrTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Material Terms of Trading Arrangement</link:label>
    <link:label id="lab_ecd_MtrlTermsOfTrdArrTextBlock_label_en-US" xlink:label="lab_ecd_MtrlTermsOfTrdArrTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Material Terms of Trading Arrangement [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_MtrlTermsOfTrdArrTextBlock" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_MtrlTermsOfTrdArrTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_MtrlTermsOfTrdArrTextBlock" xlink:to="lab_ecd_MtrlTermsOfTrdArrTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent_019e1495-bcfc-7036-b23d-0eda7097d507_terseLabel_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Additional shares greater than preferred stock, percent</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent_label_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable Prohibited, Additional Shares Greater Than Preferred Stock, Percent</link:label>
    <link:label id="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent_documentation_en-US" xlink:label="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Stock, Diviend Payable Prohibited, Additional Shares Greater Than Preferred Stock, Percent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:href="fsk-20260331.xsd#fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:to="lab_fsk_PreferredStockDiviendPayableProhibitedAdditionalSharesGreaterThanPreferredStockPercent" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019d1bac-cbe9-74a9-b399-b693785724f3_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Asset Class [Domain]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Asset Class [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:to="lab_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019d1bac-cc86-716e-b440-41a6e44bf663_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net realized gain (loss)</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:to="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInIncentiveFeePayable_019d1bac-cc86-7bca-8b58-74d85a26b15e_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInIncentiveFeePayable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase (decrease) in subordinated income incentive fees payable</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInIncentiveFeePayable_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInIncentiveFeePayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Incentive Fee Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInIncentiveFeePayable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInIncentiveFeePayable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInIncentiveFeePayable" xlink:to="lab_us-gaap_IncreaseDecreaseInIncentiveFeePayable" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OtherAggregatedInvestmentsMember_019daacf-adef-7e24-9f08-5fe837c619e3_terseLabel_en-US" xlink:label="lab_us-gaap_OtherAggregatedInvestmentsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equity/Other</link:label>
    <link:label id="lab_us-gaap_OtherAggregatedInvestmentsMember_label_en-US" xlink:label="lab_us-gaap_OtherAggregatedInvestmentsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Security Investments [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAggregatedInvestmentsMember" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAggregatedInvestmentsMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherAggregatedInvestmentsMember" xlink:to="lab_us-gaap_OtherAggregatedInvestmentsMember" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage_019d1bac-cc86-797b-9260-83d0487ee49a_terseLabel_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Joint venture voting control, percentage</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage_label_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Voting Control, Percentage</link:label>
    <link:label id="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage_documentation_en-US" xlink:label="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Investment Company, Committed Capital, Voting Control, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:href="fsk-20260331.xsd#fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:to="lab_fsk_InvestmentCompanyCommittedCapitalVotingControlPercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodValueNewIssues_019d1bac-cc86-748a-9b16-38ab446dc602_terseLabel_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Issueance of preferred stock</link:label>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodValueNewIssues_label_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Value, New Issues</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="lab_us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StatementLineItems_019d1bac-cc86-73c8-9f62-d1b72c94b1f5_terseLabel_en-US" xlink:label="lab_us-gaap_StatementLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:label id="lab_us-gaap_StatementLineItems_label_en-US" xlink:label="lab_us-gaap_StatementLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementLineItems" xlink:to="lab_us-gaap_StatementLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_VariableRateAxis_019d1bac-ccf8-785e-aa0f-94da73816749_terseLabel_en-US" xlink:label="lab_us-gaap_VariableRateAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable Rate [Axis]</link:label>
    <link:label id="lab_us-gaap_VariableRateAxis_label_en-US" xlink:label="lab_us-gaap_VariableRateAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Variable Rate [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_VariableRateAxis" xlink:to="lab_us-gaap_VariableRateAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_Rule10b51ArrAdoptedFlag_terseLabel_en-US" xlink:label="lab_ecd_Rule10b51ArrAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Rule 10b5-1 Arrangement Adopted</link:label>
    <link:label id="lab_ecd_Rule10b51ArrAdoptedFlag_label_en-US" xlink:label="lab_ecd_Rule10b51ArrAdoptedFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Rule 10b5-1 Arrangement Adopted [Flag]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_Rule10b51ArrAdoptedFlag" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_Rule10b51ArrAdoptedFlag"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_Rule10b51ArrAdoptedFlag" xlink:to="lab_ecd_Rule10b51ArrAdoptedFlag" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_019d1bac-cc86-75c4-981b-21a0f96f1d74_terseLabel_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and other assets</link:label>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_label_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019d1bac-cc86-7f83-b25d-18286713a50a_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Table]</link:label>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_label_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:type="arc" order="1"/>
    <link:label id="lab_srt_CounterpartyNameAxis_019d1bac-cc86-7f73-a863-6e9822b461a0_terseLabel_en-US" xlink:label="lab_srt_CounterpartyNameAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Counterparty Name [Axis]</link:label>
    <link:label id="lab_srt_CounterpartyNameAxis_label_en-US" xlink:label="lab_srt_CounterpartyNameAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Counterparty Name [Axis]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_CounterpartyNameAxis" xlink:to="lab_srt_CounterpartyNameAxis" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_SubsequentEventLineItems_019d1bac-cc86-7aa7-a8f1-95c3aac41925_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Subsequent Event [Line Items]</link:label>
    <link:label id="lab_us-gaap_SubsequentEventLineItems_label_en-US" xlink:label="lab_us-gaap_SubsequentEventLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Subsequent Event [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SubsequentEventLineItems" xlink:to="lab_us-gaap_SubsequentEventLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_GrossInvestmentIncomeOperating_019d1bac-cc86-7e12-93f1-2e8efcbd1249_totalLabel_en-US" xlink:label="lab_us-gaap_GrossInvestmentIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total investment income</link:label>
    <link:label id="lab_us-gaap_GrossInvestmentIncomeOperating_019d1bac-cc86-7f87-b19d-e92aab77dbfd_terseLabel_en-US" xlink:label="lab_us-gaap_GrossInvestmentIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total investment income</link:label>
    <link:label id="lab_us-gaap_GrossInvestmentIncomeOperating_label_en-US" xlink:label="lab_us-gaap_GrossInvestmentIncomeOperating" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Gross Investment Income, Operating</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_GrossInvestmentIncomeOperating" xlink:to="lab_us-gaap_GrossInvestmentIncomeOperating" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease_019d1bac-cc86-7cac-8034-ebf680c26bb3_totalLabel_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net Proceeds from Share Transactions (in shares)</link:label>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease_label_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Period Increase (Decrease)</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease" xlink:to="lab_us-gaap_StockIssuedDuringPeriodSharesPeriodIncreaseDecrease" xlink:type="arc" order="1"/>
    <link:label id="lab_fsk_EuroInterbankOfferedRateMember_019d1bac-cc86-769b-a28b-4712d3589ba3_terseLabel_en-US" xlink:label="lab_fsk_EuroInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Euro Interbank Offered Rate</link:label>
    <link:label id="lab_fsk_EuroInterbankOfferedRateMember_label_en-US" xlink:label="lab_fsk_EuroInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Euro Interbank Offered Rate [Member]</link:label>
    <link:label id="lab_fsk_EuroInterbankOfferedRateMember_documentation_en-US" xlink:label="lab_fsk_EuroInterbankOfferedRateMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Euro Interbank Offered Rate</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_fsk_EuroInterbankOfferedRateMember" xlink:href="fsk-20260331.xsd#fsk_EuroInterbankOfferedRateMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_fsk_EuroInterbankOfferedRateMember" xlink:to="lab_fsk_EuroInterbankOfferedRateMember" xlink:type="arc" order="1"/>
    <link:label id="lab_dei_EntityIncorporationStateCountryCode_019d1bac-cc86-7a41-9f5c-aa9948533d13_terseLabel_en-US" xlink:label="lab_dei_EntityIncorporationStateCountryCode" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Entity Incorporation, State or Country Code</link:label>
    <link:label id="lab_dei_EntityIncorporationStateCountryCode_label_en-US" xlink:label="lab_dei_EntityIncorporationStateCountryCode" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Incorporation, State or Country Code</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityIncorporationStateCountryCode" xlink:to="lab_dei_EntityIncorporationStateCountryCode" xlink:type="arc" order="1"/>
    <link:label id="lab_ecd_NonNeosMember_terseLabel_en-US" xlink:label="lab_ecd_NonNeosMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-NEOs</link:label>
    <link:label id="lab_ecd_NonNeosMember_label_en-US" xlink:label="lab_ecd_NonNeosMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-NEOs [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ecd_NonNeosMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_NonNeosMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ecd_NonNeosMember" xlink:to="lab_ecd_NonNeosMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019d1bac-cc86-77b6-8ae5-98513d53131c_totalLabel_en-US" xlink:label="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total increase (decrease) in cash, cash equivalents, restricted cash and foreign currency</link:label>
    <link:label id="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_label_en-US" xlink:label="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="lab_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:type="arc" order="1"/>
  </link:labelLink>
</link:linkbase>
