Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]
Nature of operations	Nature of operations - Coastal Financial Corporation (“Corporation” or “Company”) is a registered bank holding company whose wholly owned subsidiaries are Coastal Community Bank (“Bank”) and Arlington Olympic LLC (“LLC”). The Company is a Washington state corporation that was organized in 2003. The Bank was incorporated and commenced operations in 1997 and is a Washington state-chartered commercial bank that is a member bank of the Federal Reserve system. The LLC was formed in 2019 and owns the Company’s Arlington branch site, which the Bank leases from the LLC. The Company operates through the Bank and is headquartered in Everett, Washington, which by population is the largest city in Snohomish County. The Company’s business is conducted through three reportable segments: The community bank, CCBX and treasury & administration. The primary focus of the community bank is on providing a wide range of banking products and services to consumers and small to medium sized businesses in the broader Puget Sound region in the state of Washington and through the Internet and our mobile banking application. We currently operate 14 full-service banking locations, 12 of which are located in Snohomish County, where we are the largest community bank by deposit market share, and two of which are located in neighboring counties (one in King County and one in Island County). We also have a loan production office which is located in King county. The CCBX segment provides banking as a service (“BaaS”) that allows digital financial service providers, companies and brands to offer their customers banking services. The CCBX segment had a total of 30 partners, at varying stages as of March 31, 2026. The treasury & administration segment includes investments, debt and other reporting items that are not specific to the community bank or CCBX segments. The Bank’s deposits are insured in whole or in part by the Federal Deposit Insurance Corporation (“FDIC”). The community bank’s loans and deposits are primarily within the greater Puget Sound region, while CCBX loans and deposits are dependent upon the partners' markets. The Bank’s primary funding source is deposits from customers. The Bank is subject to regulation and supervision by the Board of Governors of the Federal Reserve System and the Washington State Department of Financial Institutions Division of Banks. The Federal Reserve also has regulatory and supervisory authority over the Company.
Financial statement presentation	Financial statement presentation - The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim reporting requirements and with instructions to Form 10-Q and Article 10 of Regulation S-X, and therefore do not include all the information and notes included in the annual consolidated financial statements in conformity with GAAP. These interim condensed consolidated financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes included in the Company’s Annual report on Form 10-K as filed with the U.S. Securities and Exchange Commission (“SEC”) on February 27, 2026. Operating results for the three months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the entire year. Amounts presented in the consolidated financial statements and footnote tables are rounded and presented in thousands of dollars except per-share amounts, which are presented in dollars. In the narrative footnote discussion, amounts are rounded to thousands and presented in dollars. In management’s opinion, all accounting adjustments necessary to accurately reflect the financial position and results of operations on the accompanying consolidated financial statements have been made. These adjustments include normal and recurring accruals considered necessary for a fair and accurate presentation.
Principles of consolidation	Principles of consolidation - The consolidated financial statements include the accounts of the Company, the Bank and the LLC. All significant intercompany accounts have been eliminated in consolidation.
Estimates	Estimates - The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management believes that its critical accounting policies include determining the allowance for credit losses, the valuation of the Company’s deferred tax assets, and fair value of financial instruments. Actual results could differ significantly from those estimates.
Subsequent Events	Subsequent Events - The Company has evaluated events and transactions subsequent to March 31, 2026 for potential recognition or disclosure.
Reclassifications	Reclassifications - Certain amounts reported in prior quarters' consolidated financial statements may have been reclassified to conform to the current presentation with no effect on stockholders’ equity or net income.
Recent Accounting Guidance Not Yet Effective	Recent Accounting Guidance In November 2023, the FASB issued ASU 2023-07, Income Statement—Reporting Comprehensive Income (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires enhanced disclosures about the nature of expenses included in income statement line items to improve transparency and comparability. This ASU is effective for fiscal years beginning after December 15, 2026, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the transparency of income tax disclosures by requiring more detailed information about income tax expense, cash taxes paid, and the effective tax rate reconciliation. This ASU is effective for fiscal years beginning after December 15, 2024, and interim periods within those fiscal years and was implemented by the Company as of the fiscal year ended December 31, 2025. The adoption of ASU 2023-09 did not have a material impact on the Company’s consolidated financial statements but resulted in enhanced income tax disclosures. In March 2025, the FASB issued ASU 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which simplifies the measurement of expected credit losses for certain financial assets by providing a practical expedient and additional guidance on applying CECL to short-term receivables. This ASU is effective for fiscal years beginning after December 15, 2025, and interim periods within those fiscal years, with early adoption permitted. This standard did not have a material impact on the Company's consolidated financial statements. In September 2025, the FASB issued ASU 2025-06, Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software, which modernizes and clarifies guidance on capitalization of internal-use software costs (including software developed using iterative methods) and related presentation/disclosure considerations. This ASU is effective for annual reporting periods beginning after December 15, 2027, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its capitalization policies and disclosures. In November 2025, the FASB issued ASU 2025-08, Financial Instruments—Credit Losses (Topic 326): Purchased Loans, which expands and clarifies acquisition-date accounting for certain purchased loans under CECL, including use of a gross-up approach for specified acquired loans. This ASU is effective for annual reporting periods beginning after December 15, 2026, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its accounting for acquired loans and related disclosures. In November 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements, to clarify and improve the guidance related to interim financial reporting. The ASU enhances the structure and navigability of Topic 270 by consolidating and organizing interim disclosure requirements and clarifying their applicability to entities that issue interim financial statements in accordance with U.S. GAAP. The amendments also introduce a disclosure principle requiring entities to disclose material events and changes that occur after the most recent annual reporting period. The ASU does not significantly expand existing disclosure requirements but is intended to improve transparency and consistency in interim reporting. This ASU is effective for interim reporting periods in fiscal years beginning after December 15, 2027, and early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard on its consolidated financial statements.

Description of Business and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2026

Nature of operations - Coastal Financial Corporation (“Corporation” or “Company”) is a registered bank holding company whose wholly owned subsidiaries are Coastal Community Bank (“Bank”) and Arlington Olympic LLC (“LLC”). The Company is a Washington state corporation that was organized in 2003. The Bank was incorporated and commenced operations in 1997 and is a Washington state-chartered commercial bank that is a member bank of the Federal Reserve system. The LLC was formed in 2019 and owns the Company’s Arlington branch site, which the Bank leases from the LLC.

The Company operates through the Bank and is headquartered in Everett, Washington, which by population is the largest city in Snohomish County. The Company’s business is conducted through three reportable segments: The community bank, CCBX and treasury & administration. The primary focus of the community bank is on providing a wide range of banking products and services to consumers and small to medium sized businesses in the broader Puget Sound region in the state of Washington and through the Internet and our mobile banking application. We currently operate 14 full-service banking locations, 12 of which are located in Snohomish County, where we are the largest community bank by deposit market share, and two of which are located in neighboring counties (one in King County and one in Island County). We also have a loan production office which is located in King county. The CCBX segment provides banking as a service (“BaaS”) that allows digital financial service providers, companies and brands to offer their customers banking services. The CCBX segment had a total of 30 partners, at varying stages as of March 31, 2026. The treasury & administration segment includes investments, debt and other reporting items that are not specific to the community bank or CCBX segments.

The Bank’s deposits are insured in whole or in part by the Federal Deposit Insurance Corporation (“FDIC”). The community bank’s loans and deposits are primarily within the greater Puget Sound region, while CCBX loans and deposits are dependent upon the partners' markets. The Bank’s primary funding source is deposits from customers. The Bank is subject to regulation and supervision by the Board of Governors of the Federal Reserve System and the Washington State Department of Financial Institutions Division of Banks. The Federal Reserve also has regulatory and supervisory authority over the Company.

Financial statement presentation

Financial statement presentation - The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim reporting requirements and with instructions to Form 10-Q and Article 10 of Regulation S-X, and therefore do not include all the information and notes included in the annual consolidated financial statements in conformity with GAAP. These interim condensed consolidated financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes included in the Company’s Annual report on Form 10-K as filed with the U.S. Securities and Exchange Commission (“SEC”) on February 27, 2026. Operating results for the three months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the entire year.

Amounts presented in the consolidated financial statements and footnote tables are rounded and presented in thousands of dollars except per-share amounts, which are presented in dollars. In the narrative footnote discussion, amounts are rounded to thousands and presented in dollars.

In management’s opinion, all accounting adjustments necessary to accurately reflect the financial position and results of operations on the accompanying consolidated financial statements have been made. These adjustments include normal and recurring accruals considered necessary for a fair and accurate presentation.

Principles of consolidation

Principles of consolidation - The consolidated financial statements include the accounts of the Company, the Bank and the LLC. All significant intercompany accounts have been eliminated in consolidation.

Estimates

Estimates - The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management believes that its critical accounting policies include determining the allowance for credit losses, the valuation

of the Company’s deferred tax assets, and fair value of financial instruments. Actual results could differ significantly from those estimates.

Subsequent Events

Subsequent Events - The Company has evaluated events and transactions subsequent to March 31, 2026 for potential recognition or disclosure.

Reclassifications

Reclassifications - Certain amounts reported in prior quarters' consolidated financial statements may have been reclassified to conform to the current presentation with no effect on stockholders’ equity or net income.

Recent Accounting Guidance Not Yet Effective

Recent Accounting Guidance

In November 2023, the FASB issued ASU 2023-07, Income Statement—Reporting Comprehensive Income (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires enhanced disclosures about the nature of expenses included in income statement line items to improve transparency and comparability. This ASU is effective for fiscal years beginning after December 15, 2026, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its disclosures.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the transparency of income tax disclosures by requiring more detailed information about income tax expense, cash taxes paid, and the effective tax rate reconciliation. This ASU is effective for fiscal years beginning after December 15, 2024, and interim periods within those fiscal years and was implemented by the Company as of the fiscal year ended December 31, 2025. The adoption of ASU 2023-09 did not have a material impact on the Company’s consolidated financial statements but resulted in enhanced income tax disclosures.

In March 2025, the FASB issued ASU 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which simplifies the measurement of expected credit losses for certain financial assets by providing a practical expedient and additional guidance on applying CECL to short-term receivables. This ASU is effective for fiscal years beginning after December 15, 2025, and interim periods within those fiscal years, with early adoption permitted. This standard did not have a material impact on the Company's consolidated financial statements.

In September 2025, the FASB issued ASU 2025-06, Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software, which modernizes and clarifies guidance on capitalization of internal-use software costs (including software developed using iterative methods) and related presentation/disclosure considerations. This ASU is effective for annual reporting periods beginning after December 15, 2027, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its capitalization policies and disclosures.

In November 2025, the FASB issued ASU 2025-08, Financial Instruments—Credit Losses (Topic 326): Purchased Loans, which expands and clarifies acquisition-date accounting for certain purchased loans under CECL, including use of a gross-up approach for specified acquired loans. This ASU is effective for annual reporting periods beginning after December 15, 2026, and interim periods within those fiscal years, with early adoption permitted. The Company is evaluating the impact of this standard on its accounting for acquired loans and related disclosures.

In November 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements, to clarify and improve the guidance related to interim financial reporting. The ASU enhances the structure and navigability of Topic 270 by consolidating and organizing interim disclosure requirements and clarifying their applicability to entities that issue interim financial statements in accordance with U.S. GAAP. The amendments also introduce a disclosure principle requiring entities to disclose material events and changes that occur after the most recent annual reporting period. The ASU does not significantly expand existing disclosure requirements but is intended to improve transparency and consistency in interim reporting. This ASU is effective for interim reporting periods in fiscal years beginning after December 15, 2027, and early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard on its consolidated financial statements.