UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): June 16, 2025

BYLINE BANCORP, INC.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

(State or Other Jurisdiction

of Incorporation)

(773) 244-7000

(Registrant’s Telephone Number, Including Area Code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 4.01. Changes in Registrant's Certifying Accountant.

On June 16, 2025, Byline Bancorp, Inc. (the "Company") was notified that Moss Adams LLP ("Moss Adams"), the Company's independent registered public accounting firm, merged with Baker Tilly US, LLP effective on June 3, 2025. The combined audit practices operate as Baker Tilly US, LLP ("Baker Tilly"). In connection with the notification of the merger, Moss Adams has resigned as the auditors of the Company and the Audit Committee of the Company's Board of Directors approved the appointment of Baker Tilly, as the successor to Moss Adams, as the Company's independent registered public accounting firm.

The audit reports of Moss Adams on the Company's consolidated financial statements for the years ended December 31, 2024 and 2023, and internal control over financial reporting as of December 31, 2024, did not contain an adverse opinion or a disclaimer of opinion, nor were they qualified or modified as to uncertainty, audit scope or accounting principles.

During the years ended December 31, 2024 and 2023, and the subsequent interim period through June 16, 2025, there were no (a) disagreements with Moss Adams on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which, if not resolved to Moss Adams' satisfaction, would have caused it to make reference to the subject matter of the disagreement in connection with its reports on the Company's financial statements, or (b) reportable events requiring disclosure pursuant to Item 304(a)(1)(v) of Regulation S-K.

During the years ended December 31, 2024 and 2023, and the subsequent interim period through the date of this Current Report on Form 8-K, neither the Company, nor anyone on its behalf, consulted with Baker Tilly regarding: (i) either the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on the Company's financial statements or (ii) any matter that was either the subject of a "disagreement," as defined in Item 304(a)(1)(iv) of Regulation S-K and the related instructions to that item, or a "reportable event," as described in Item 304(a)(1)(v) of Regulation S-K.

The Company provided Moss Adams with a copy of this Current Report on Form 8-K prior to its filing with the Securities and Exchange Commission (the "Commission") and requested that Moss Adams furnish the Company with a letter addressed to the Commission stating whether it agrees with the above statements and, if it does not agree, the respects in which it does not agree. A copy of Moss Adams' letter to the Commission, dated June 17, 2025, is filed as Exhibit 16.1 to this Form 8-K and is incorporated herein by reference.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.