8-K

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): March 4, 2024

ISABELLA BANK CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (989) 772-9471

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:

| ☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) | | --- | --- || ☐ | Soliciting material pursuant to Rule l4a-12 under the Exchange Act (17 CFR 240.l4a-l2) | | --- | --- || ☐ | Pre-commencement communications pursuant to Rule l4d-2(b) under the Exchange Act (17 CFR 240.l4d-2(b)) | | --- | --- || ☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.l3e-4(c)) | | --- | --- |

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).

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. ☐

Section 4 - Matters Related to Accountants and Financial Statements

Item 4.01 Changes in Registrant's Certifying Accountant.

(a)    On March 4, 2024, Rehmann Robson LLC ("Rehmann") informed Isabella Bank Corporation (the "Corporation") that Rehmann is declining to stand for re-appointment as the Corporation's independent registered public accounting firm after completion of the audit of the fiscal year ending December 31, 2024 as a result of Rehmann's decision to exit the integrated audit portion of its Securities and Exchange Commission assurance practice. There is no dispute between the Corporation and Rehmann, and Rehmann will continue to serve as the Corporation’s independent registered public accounting firm with respect to the audit of the fiscal year ended December 31, 2024.

The reports of Rehmann on the consolidated financial statements of the Corporation as of and for the fiscal years ended December 31, 2023 and 2022 contained no adverse opinion or disclaimer of opinion and were not qualified or modified as to uncertainty, audit scope, or accounting principles. During the fiscal years ended December 31, 2023 and 2022, and in the interim period from January 1, 2024 through March 4, 2024, (i) there were no disagreements between the Corporation and Rehmann on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreement(s), if not resolved to the satisfaction of Rehmann, would have caused Rehmann to make reference to such disagreements in its report on the consolidated financial statements for such years; and (ii) there were no “reportable events” as such term is defined in Item 304(a)(1)(v) of Regulation S-K).

The Corporation has provided Rehmann with a copy of the disclosures made in this Current Report on Form 8-K prior to its filing with the Securities and Exchange Commission. A copy of Rehmann's letter dated March 8, 2024, stating that Rehmann agrees with the statements made herein, is attached as Exhibit 16.1 hereto.

The Corporation will disclose its engagement of a new independent registered public accounting firm once the evaluation process has been completed and as required by, and in accordance with, the Securities and Exchange Commission’s rules and regulations.

Section 9 - Financial Statements and Exhibits

Item 9.01 Financial Statements and Exhibits.

(d)    Exhibits:

SIGNATURES

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.

INDEX TO EXHIBITS

Document

Exhibit 16.1

March 8, 2024

Securities and Exchange Commission

100 F Street NE

Washington, DC 20549

Commissioners:

On March 4, 2024, we provided notice to Isabella Bank Corporation (the “Company”) of our decision to not stand for reelection as the Company’s independent registered public accounting firm with respect to the integrated audit and interim review engagements of the Company after completion of the integrated audit of the 2024 consolidated financial statements and internal control over financial reporting.

We have read the statements made by the Company pursuant to Item 4.01 of Form 8-K, which, Form 8-K we understand will be filed with the Securities and Exchange Commission on March 8, 2024 and are in agreement with the disclosures in the referenced Form 8-K, insofar as they pertain to our firm. We have not been requested to provide, nor are we providing, any representations related to the other disclosures included in this Form 8-K.

Respectfully,

/s/ Rehmann Robson LLC

Rehmann Robson LLC