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): January 1, 2026

Timberland Bancorp, Inc.

(Exact name of registrant as specified in its charter)

Washington	0-23333	91-1863696
State or other jurisdiction Of incorporation	Commission File Number	(I.R.S. Employer Identification No.)

Registrant’s telephone number (including area code) (360) 533-4747

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $.01 per share		TSBK		The Nasdaq Stock Market LLC

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. [ ]

On January 1, 2026, Timberland Bancorp, Inc. (the “Company”) was notified that Delap LLP (“Delap”), the Company's independent registered public accounting firm, merged with Aprio, LLP effective on January 1, 2026. The combined audit practices operate as Aprio, LLP (“Aprio”). In connection with the notification of the merger, Delap has resigned as the auditors of the Company and the Audit Committee of the Company’s Board of Directors approved the appointment of Aprio, as the successor to Delap, as the Company’s independent registered public accounting firm.

The audit reports of Delap on the Company’s consolidated financial statements for the fiscal years ended September 30, 2025 and 2024, and for each of the years in the three-year period ended September 30, 2025, and internal control over financial reporting as of September 30, 2025, 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 fiscal years ended September 30, 2025 and 2024, and the subsequent interim period through January 1, 2026, there were no (a) disagreements with Delap on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which, if not resolved to Delap’s 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 September 30, 2025 and 2024, 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 Aprio 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 Delap 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 Delap 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 Delap’s letter to the Commission, dated January 7, 2026, is filed as Exhibit 16.1 to this Form 8-K and is incorporated herein by reference.

16.1        Letter from Delap LLP, dated January 7, 2026

104         Cover Page Interactive Data File (embedded within the Inline XBRL document)

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, hereunto duly authorized.

	TIMBERLAND BANCORP, INC.
DATE:  January 7, 2026	By:  /s/ Marci A. Basich
	Marci A. Basich         Chief Financial Officer

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