FIRST BUSINESS FINANCIAL SERVICES, INC.

Shareholders and the Board of Directors

Madison, Wisconsin

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated balance sheets of First Business Financial Services, Inc. (the "Corporation") as of December 31, 2025 and 2024, the related consolidated statements of income, comprehensive income, stockholders’ equity, and cash flows for each of the years in the three-year period ended December 31, 2025, and the related notes (collectively referred to as the "financial statements"). We also have audited the Corporation’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control – Integrated Framework: (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the financial statements referred to above present fairly, in all material respects, the financial position of the Corporation as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the years in the three-year period ended December 31, 2025 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Corporation maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control – Integrated Framework: (2013) issued by COSO.

Basis for Opinions

The Corporation’s management is responsible for these financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Annual Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Corporation’s financial statements and an opinion on the Corporation’s internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Corporation in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the financial statements included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Allowance and Provision for Credit Losses – Qualitative Factors

The allowance for credit losses (the “ACL”) is an accounting estimate of expected credit losses over the estimated life of financial assets carried at amortized cost and off-balance-sheet credit exposures in accordance with ASC 326. The estimates of expected credit losses on loans are based on relevant information about past events, current conditions, and reasonable and supportable forecasts regarding the collectability of the remaining cash flows over the contractual term of the loans. The Corporation utilized a discounted cash flow model to estimate the quantitative component of the allowance for credit losses for loans using key inputs and assumptions such as probability of default, loss given default, prepayment and curtailment rates, and forecast model.

The quantitative model was adjusted with qualitative factors, including but not limited to: management’s ongoing review and grading of the loan and lease portfolios, consideration of delinquency experience, changes in the size of the loan and lease portfolios, existing economic conditions, level of loans and leases subject to more frequent review by management, changes in underlying collateral, concentrations of loans to specific industries, and other qualitative factors that could affect credit losses. The determination of qualitative factors involves significant management judgment and the use of subjective assumptions.

We identified auditing the qualitative factors as a critical audit matter because of the high degree of auditor judgment and auditor effort required to evaluate management's judgments in their determination of the qualitative factors.

The primary procedures we performed to address this critical audit matter included:

Testing the effectiveness of controls over the evaluation of the qualitative factors, including controls addressing:

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The reliability and relevance of data used as the basis for the adjustments relating to qualitative factors;

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The reasonableness of management’s judgments and assumptions related to the assessed level of risk and the ending allocation of the qualitative factors;

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The mathematical accuracy of the dollar amount applied to the qualitative factors;

Substantively testing management’s process, including evaluating their judgments and assumptions, for developing the qualitative factors, which included:

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Evaluation of the reliability and relevance of data used as a basis for the adjustments relating to qualitative factors;

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Evaluation of the reasonableness of management’s judgments and assumptions related to the assessed level of risk for the qualitative factors and the resulting allocation;

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Evaluation of the mathematical accuracy of the adjustment factors for the qualitative component and the dollar amount of the reserve derived from the qualitative factor assessment;

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Tracing the allowance allocation from the qualitative factor analysis to the overall allowance calculation.

/s/Crowe LLP

We have served as the Corporation's auditor since 2017, which is the year the engagement letter was signed for the audit of the 2018 financial statements.

Oakbrook Terrace, Illinois

February 25, 2026