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): January 5, 2026

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 5 - Corporate Governance and Management

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

(c)    Appointment of Gerald J. Ritzert as Chief Financial Officer

On January 5, 2026, Gerald J. Ritzert was appointed as the Chief Financial Officer of Isabella Bank Corporation. Mr. Ritzert, age 56, has over 30 years of experience in accounting and finance, including significant leadership roles in the banking industry. Mr. Ritzert's most recent position was Executive Vice President and Chief Financial Officer of First National Bank and Trust in Beloit, Wisconsin, since 2021. Mr. Ritzert previously was the Chief Financial Officer of Dollar Bank, FSB in Pittsburgh, Pennsylvania.

In connection with Mr. Ritzert's appointment, effective January 5, 2026, Neil M. McDonnell, President of Isabella Bank, Isabella Bank Corporation's wholly-owned subsidiary, is no longer acting as the Interim Chief Financial Officer of Isabella Bank Corporation. Mr. McDonnell held the titles of Isabella Bank President and Interim Chief Financial Officer since August 28, 2025.

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 99.1

For Immediate Release

Isabella Bank Corporation

401 N. Main Street

Mt. Pleasant, MI 48858-1649

FOR MORE INFORMATION CONTACT:

Lori Peterson, Vice President and Director of Marketing

Phone: 989-779-6333 | lapeterson@isabellabank.com

Ritzert Joins Isabella Bank Corporation as Chief Financial Officer

Mt. Pleasant, MI, January 5, 2026 — Isabella Bank Corporation proudly announces the appointment of Gerald J. Ritzert, CPA as its Chief Financial Officer, effective January 5, 2026.

Jerome Schwind, President and Chief Executive Officer of Isabella Bank Corporation, shared his enthusiasm for Ritzert’s arrival. "We are excited to welcome Jerry to our leadership team. His extensive banking experience and proven ability to drive financial performance and strategic growth will be invaluable as we continue to strengthen Isabella Bank’s position in the marketplace."

Ritzert brings a wealth of experience accumulated over more than 30 years in accounting and finance, including significant leadership roles in the banking industry. His expertise spans asset-liability management, capital planning, investment portfolio optimization, and strategic financial reporting. Throughout his career, Ritzert has successfully implemented initiatives to enhance profitability, strengthen risk management, and improve operational efficiency.

Ritzert earned a Bachelor of Science in Business Administration – Accounting from Robert Morris College in Pittsburgh, Pennsylvania, and is a Certified Public Accountant, underscoring his commitment to excellence and integrity in financial leadership. He has served on multiple boards and committees, including the Greater Beloit Economic Development Council and the Financial Managers Society.

Jerry and his wife, Laure, are excited to relocate from Roscoe, Illinois, to Mount Pleasant. Originally from Pittsburgh, Pennsylvania, they look forward to becoming active members of the Isabella Bank community.

Isabella Bank Corporation (Nasdaq: ISBA) is the parent holding company of Isabella Bank, a state-chartered community bank headquartered in Mt. Pleasant, Michigan. Isabella Bank was established in 1903 and has been committed to serving the local banking needs of its customers and communities for over 121 years. The Bank offers personal and commercial lending and deposit products, as well as investment, trust, and estate planning services through Isabella Wealth. The Bank has locations throughout eight Mid-Michigan counties: Bay, Clare, Gratiot, Isabella, Mecosta, Midland, Montcalm, and Saginaw.