FIRST BUSINESS FINANCIAL SERVICES, INC. 10-Q

Item 5. Other Information During the three months ended March 31, 2026 , no director or “officer” of the Corporation adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K. 57 Table of Contents Item 6. Exhibits 31.1 Certification of the Chief Executive Officer 31.2 Certification of the Chief Financial Officer 32 Certification of the Chief Executive Officer and Chief Financial Officer pursuant to 18 U.S.C. Section 1350 101 The following financial information from First Business Financial Services, Inc.’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, formatted in XBRL (eXtensible Business Reporting Language): (i) Consolidated Balance Sheets as of March 31, 2026 and December 31, 2025, (ii) Consolidated Statements of Income for the three months ended March 31, 2026 and 2025, (iii) Consolidated Statements of Comprehensive Income for the three months ended March 31, 2026 and 2025, (iv) Consolidated Statements of Changes in Stockholders’ Equity for the three months ended March 31, 2026 and 2025, (v) Consolidated Statements of Cash Flows for the three months ended March 31, 2026 and 2025, and (vi) the Notes to Unaudited Consolidated Financial Statements 104 The cover page from First Business Financial Services, Inc.’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2026 has been formatted in Inline XBRL and contained in Exhibit 101. 58 Table of Contents Signa tures Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. FIRST BUSINESS FINANCIAL SERVICES, INC. April 24, 2026 /s/ Corey A. Chambas Corey A. Chambas Chief Executive Officer April 24, 2026 /s/ Brian D. Spielmann Brian D. Spielmann Chief Financial Officer (principal financial officer) 59