Nature of Business Activities and Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]
Nature of Operations and Consolidation	The consolidated financial statements include Burke & Herbert Financial Services Corp. (“Burke & Herbert”) and its wholly-owned subsidiary Burke & Herbert Bank & Trust Company (“the Bank”), together referred to as “the Company” for purposes of the Notes to the Financial Statements. As of close of the calendar year 2025, we ceased to be an emerging growth company and became a large accelerated filer. Therefore, we are no longer exempt from the requirements under Section 404 of the Sarbanes-Oxley Act and are no longer able to take advantage of exemptions from various public company reporting requirements applicable to emerging growth companies. The consolidated financial statements include the accounts of the Company and the Bank (as its wholly-owned subsidiary). All significant intercompany accounts and transactions between the Company and the Bank have been eliminated.
Basis of Presentation	The accompanying consolidated financial statements include Burke & Herbert Financial Services Corp. and its wholly owned subsidiary Burke & Herbert Bank & Trust Company and have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial reporting and with applicable quarterly reporting regulations of the U.S. Securities and Exchange Commission (“SEC”). The accounting and reporting policies of the Company conform to GAAP and reflect practices of the banking industry. They do not include all of the information and notes required by GAAP for complete financial statements. As such, these unaudited financial statements should be read in conjunction with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2025, included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2026.
Adoption of new accounting standards and Newly issued not yet adopted accounting standards	Adoption of new accounting standards In November 2025, the FASB issued ASU 2025-08, Financial Instruments - Credit Losses (Topic 326): Purchased Loans. This ASU amends the accounting for certain acquired loans by expanding the use of the “gross‑up” approach under the CECL model to include purchased seasoned loans. Under this approach, the allowance for expected credit losses is recognized at the acquisition date as an adjustment to the loan’s amortized cost basis, rather than through a provision for credit losses, thereby eliminating a “day‑one” credit loss expense for loans within the scope of the guidance. The amendments do not change the accounting for purchased credit‑deteriorated loans, originated loans, credit card loans, or debt securities. The amendments in this update are effective for fiscal years beginning after December 15, 2026, including interim periods within those fiscal years, and are to be applied on a prospective basis. Early adoption is permitted. As permitted, the Company has elected to early adopt the amended guidance on January 1, 2026 on a prospective basis. The Company expects that substantially all the loans acquired in the LNKB Merger will be considered seasoned. Newly issued not yet adopted accounting standards In November 2024, the FASB issued ASU 2024-03, Income Statement (Subtopic 220-40): Reporting Comprehensive Income—Expense Disaggregation Disclosures. This ASU seeks to improve disclosures about a public business entity’s expenses and addresses requests from investors for more detailed information about the types of expenses in commonly presented expense captions. The amendments in this update are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. This ASU is not expected to have a material impact on our consolidated financial statements. In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. This ASU incorporates certain amendments to SEC disclosure requirements into the FASB Accounting Standards Codification. The amendments in the ASU are expected to clarify or improve disclosure and presentation requirements of a variety of Codification Topics, allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the requirements, and align the requirements in the Codification with the SEC’s regulations. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC’s removal of the related disclosure requirement becomes effective. For all other entities, the effective date will be two years after the date of such removal. However, if by June 30, 2027, the SEC has not removed the related disclosure from its regulations, the amendments will be removed from the Codification and not become effective for any entity. We do not expect the adoption of ASU 2023-06 to have a material impact on our consolidated financial statements.
Fair Value Measurements	Fair value is the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values: Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date. Level 2 – Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. Level 3 – Significant unobservable inputs that reflect our own assumptions that market participants would use in pricing an asset or liability. In instances in which multiple levels of inputs are used to measure fair value, hierarchy classification is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. The Company used the following methods and significant assumptions to estimate fair value: Investment securities The fair values for investment securities are determined by quoted market prices, if available (Level 1). For securities where quoted prices are not available, fair values are calculated based on market prices of similar securities (Level 2), using matrix pricing. Matrix pricing is a mathematical technique commonly used to price debt securities without relying exclusively on quoted prices for the specific securities but rather by relying on securities’ relationship to other benchmark quoted securities (Level 2 inputs). For securities where quoted prices or market prices of similar securities are not available, fair values are calculated using discounted cash flows or other market indicators (Level 3). Equity Investments Equity investments are recorded at fair value on a recurring basis, with changes in fair value reported in net income. Through the Summit Merger we acquired an investment in an S&P 500 index mutual fund that is traded on an exchange, and we classify it as Level 2 as of March 31, 2026. Through the Summit Merger, we acquired perpetual preferred stock of a bank holding company issued in October 2022 in a private offering. The perpetual preferred stock does not trade on an exchange or in an active over-the-counter market; therefore, we estimate its fair value using the present value of its future cash flows using observed discount rates of similar publicly-traded securities, adjusted for a liquidity premium. We classify the perpetual preferred stock as Level 2. Equity securities without readily determinable fair values are carried at cost, minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for an identical or similar investment. Such equity securities are included in other assets on the accompanying Consolidated Balance Sheets. Derivatives The fair values of derivatives are based on valuation models using observable market data as of the measurement date (Level 2). The Company has contracted with a third-party vendor to provide valuations for interest rate swaps using standard swap valuation techniques. The Company has considered counterparty credit risk in the valuation of its interest rate swap assets and has considered its own credit risk in the valuation of its interest rate swap liabilities. Loans held-for-sale The fair value of loans held-for-sale is determined using quoted prices for similar assets, adjusted for specific attributes of that loan (Level 2). These loans currently consist of one-to-four family residential loans originated for sale in the secondary market. Collateral dependent loans Loans for which the borrower is experiencing financial difficulty and repayment is dependent upon the operation or sale of collateral, are considered collateral-dependent. For collateral-dependent loans, the fair value is measured based on the value of the collateral securing the loans, less estimated costs of disposal. Collateral may be in the form of real estate or business assets, including equipment, inventory, and accounts receivable. The vast majority of the collateral underlying collateral-dependent loans is real estate, the fair value of which is measured through an appraisal. The appraisals of the collateral supporting collateral-dependent loans may utilize a single valuation approach or a combination of approaches, including comparable sales and the income approach. Any fair value adjustments are recorded in the period incurred as provision for (recapture of) credit losses on the Consolidated Statements of Income. Non-real estate collateral may be valued using an appraisal, net book value per the borrower’s financial statements, or aging reports, adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation, and management’s expertise and knowledge of the client and client’s business. Other real estate owned Assets acquired through foreclosure or other proceedings are initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. The fair value of foreclosed properties is determined on a nonrecurring basis generally utilizing current appraisals performed by an independent, licensed appraiser applying an income or market value approach using observable market data. Updated appraisals of foreclosed properties are generally obtained if the existing appraisal is more than 18 months old or more frequently if there is a known deterioration in value. However, if a current appraisal is not available, the original appraised value is discounted, as appropriate, to compensate for the estimated depreciation in the value of the real estate since the date of its original appraisal. Such discounts are generally estimated based upon management’s knowledge of sales of similar property within the applicable market area and its knowledge of other real estate market-related data as well as general economic trends. Upon foreclosure, any fair value adjustment is charged against the allowance for credit losses on loans. Subsequent fair value adjustments are recorded in the period incurred and included in other noninterest expense in the Consolidated Statements of Income.

Nature of Business Activities and Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2026

The consolidated financial statements include Burke & Herbert Financial Services Corp. (“Burke & Herbert”) and its wholly-owned subsidiary Burke & Herbert Bank & Trust Company (“the Bank”), together referred to as “the Company” for purposes of the Notes to the Financial Statements. As of close of the calendar year 2025, we ceased to be an emerging growth company and became a large accelerated filer. Therefore, we are no longer exempt from the requirements under Section 404 of the Sarbanes-Oxley Act and are no longer able to take advantage of exemptions from various public company reporting requirements applicable to emerging growth companies.

The consolidated financial statements include the accounts of the Company and the Bank (as its wholly-owned subsidiary). All significant intercompany accounts and transactions between the Company and the Bank have been eliminated.

Basis of Presentation

The accompanying consolidated financial statements include Burke & Herbert Financial Services Corp. and its wholly owned subsidiary Burke & Herbert Bank & Trust Company and have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial reporting and with applicable quarterly reporting regulations of the U.S. Securities and Exchange Commission (“SEC”). The accounting and reporting

policies of the Company conform to GAAP and reflect practices of the banking industry. They do not include all of the information and notes required by GAAP for complete financial statements. As such, these unaudited financial statements should be read in conjunction with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2025, included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2026.

Adoption of new accounting standards and Newly issued not yet adopted accounting standards

Adoption of new accounting standards

In November 2025, the FASB issued ASU 2025-08, Financial Instruments - Credit Losses (Topic 326): Purchased Loans. This ASU amends the accounting for certain acquired loans by expanding the use of the “gross‑up” approach under the CECL model to include purchased seasoned loans. Under this approach, the allowance for expected credit losses is recognized at the acquisition date as an adjustment to the loan’s amortized cost basis, rather than through a provision for credit losses, thereby eliminating a “day‑one” credit loss expense for loans within the scope of the guidance. The amendments do not change the accounting for purchased credit‑deteriorated loans, originated loans, credit card loans, or debt securities. The amendments in this update are effective for fiscal years beginning after December 15, 2026, including interim periods within those fiscal years, and are to be applied on a prospective basis. Early adoption is permitted. As permitted, the Company has elected to early adopt the amended guidance on January 1, 2026 on a prospective basis. The Company expects that substantially all the loans acquired in the LNKB Merger will be considered seasoned.

Newly issued not yet adopted accounting standards

In November 2024, the FASB issued ASU 2024-03, Income Statement (Subtopic 220-40): Reporting Comprehensive Income—Expense Disaggregation Disclosures. This ASU seeks to improve disclosures about a public business entity’s expenses and addresses requests from investors for more detailed information about the types of expenses in commonly presented expense captions. The amendments in this update are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. This ASU is not expected to have a material impact on our consolidated financial statements.

In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. This ASU incorporates certain amendments to SEC disclosure requirements into the FASB Accounting Standards Codification. The amendments in the ASU are expected to clarify or improve disclosure and presentation requirements of a variety of Codification Topics, allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the requirements, and align the requirements in the Codification with the SEC’s regulations. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC’s removal of the related disclosure requirement becomes effective. For all other entities, the effective date will be two years after the date of such removal. However, if by June 30, 2027, the SEC has not removed the related disclosure from its regulations, the amendments will be removed from the Codification and not become effective for any entity. We do not expect the adoption of ASU 2023-06 to have a material impact on our consolidated financial statements.

Fair Value Measurements

Fair value is the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values:

Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date.

Level 2 – Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

Level 3 – Significant unobservable inputs that reflect our own assumptions that market participants would use in pricing an asset or liability.

In instances in which multiple levels of inputs are used to measure fair value, hierarchy classification is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability.

The Company used the following methods and significant assumptions to estimate fair value:

Investment securities

The fair values for investment securities are determined by quoted market prices, if available (Level 1). For securities where quoted prices are not available, fair values are calculated based on market prices of similar securities (Level 2), using matrix pricing. Matrix pricing is a mathematical technique commonly used to price debt securities without relying exclusively on quoted prices for the specific securities but rather by relying on securities’ relationship to other benchmark quoted securities (Level 2 inputs). For securities where quoted prices or market prices of similar securities are not available, fair values are calculated using discounted cash flows or other market indicators (Level 3).

Equity Investments

Equity investments are recorded at fair value on a recurring basis, with changes in fair value reported in net income. Through the Summit Merger we acquired an investment in an S&P 500 index mutual fund that is traded on an exchange, and we classify it as Level 2 as of March 31, 2026.

Through the Summit Merger, we acquired perpetual preferred stock of a bank holding company issued in October 2022 in a private offering. The perpetual preferred stock does not trade on an exchange or in an active over-the-counter market; therefore, we estimate its fair value using the present value of its future cash flows using observed discount rates of similar publicly-traded securities, adjusted for a liquidity premium. We classify the perpetual preferred stock as Level 2.

Equity securities without readily determinable fair values are carried at cost, minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for an identical or similar investment. Such equity securities are included in other assets on the accompanying Consolidated Balance Sheets.

Derivatives

The fair values of derivatives are based on valuation models using observable market data as of the measurement date (Level 2). The Company has contracted with a third-party vendor to provide valuations for interest rate swaps using standard swap valuation techniques. The Company has considered counterparty credit risk in the valuation of its interest rate swap assets and has considered its own credit risk in the valuation of its interest rate swap liabilities.

Loans held-for-sale

The fair value of loans held-for-sale is determined using quoted prices for similar assets, adjusted for specific attributes of that loan (Level 2). These loans currently consist of one-to-four family residential loans originated for sale in the secondary market.

Collateral dependent loans

Loans for which the borrower is experiencing financial difficulty and repayment is dependent upon the operation or sale of collateral, are considered collateral-dependent. For collateral-dependent loans, the fair value is measured based on the value of the collateral securing the loans, less estimated costs of disposal. Collateral may be in the form of real estate or business assets, including equipment, inventory, and accounts receivable. The vast majority of the collateral underlying collateral-dependent loans is real estate, the fair value of which is measured through an appraisal. The appraisals of the collateral supporting collateral-dependent loans may utilize a single valuation approach or a combination of approaches, including comparable sales and the income approach. Any fair value adjustments are recorded in the period incurred as provision for (recapture of) credit losses on the Consolidated Statements of Income. Non-real estate collateral may be valued using an appraisal, net book value per the borrower’s financial statements, or aging reports, adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation, and management’s expertise and knowledge of the client and client’s business.

Other real estate owned

Assets acquired through foreclosure or other proceedings are initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. The fair value of foreclosed properties is determined on a nonrecurring basis generally utilizing current appraisals performed by an independent, licensed appraiser applying an income or market value approach using observable market data. Updated appraisals of foreclosed properties are generally obtained if the existing appraisal is more than 18 months old or more frequently if there is a known deterioration in value. However, if a current appraisal is not available, the original appraised value is discounted, as appropriate, to compensate for the estimated depreciation in the value of the real estate since the date of its original appraisal. Such discounts are generally estimated based upon management’s knowledge of sales of similar property within the applicable market area and its knowledge of other real estate market-related data as well as general economic trends. Upon foreclosure, any fair value adjustment is charged against the allowance for credit losses on loans. Subsequent fair value adjustments are recorded in the period incurred and included in other noninterest expense in the Consolidated Statements of Income.