isba-20260612

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 1934ct of 1934

Date of Report (Date of earliest event reported): June 12, 2026

ISABELLA BANK CORPORATION

(Exact name of registrant as specified in its charter)

Michigan

000-18415

38-2830092

(State or other jurisdiction
of incorporation or organization)

(Commission
File Number)

(IRS Employer
Identification No.)


401 North Main Street
Mt. Pleasant,	Michigan	48858-1649
(Address of principal executive offices)		(Zip Code)

(989) 772-9471

(Registrant’s telephone number)

N/A

(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):


☒			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:


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common stock, no par value per share	ISBA	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 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).


			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 7.01 - Regulation FD Disclosure

On June 11, 2026, Isabella Bank Corporation, a Michigan corporation (“Isabella”), 401 Merger Sub, Inc., a Michigan corporation and a direct, wholly owned subsidiary of Isabella, and Grand River Commerce, Inc., a Michigan corporation (“Grand River”), entered into an Agreement and Plan of Merger (the “Merger Agreement”). On June 12, 2026, Isabella and Grand River issued a joint press release announcing the execution of the Merger Agreement. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

In addition, Isabella is providing supplemental information regarding the proposed transaction. A copy of the investor presentation is furnished as Exhibit 99.2 to this Current Report on Form 8-K.

The information in this Item 7.01 and Exhibits 99.1 and 99.2 is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth in such filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits:


Exhibit No						Description

Exhibit 99.1						Joint Press Release, dated June 12, 2026
Exhibit 99.2						Investor Presentation
Exhibit 104						Cover Page Interactive Data File (embedded within the Inline XBRL document)

Forward-Looking Statements

This Current Report on Form 8-K and the exhibits filed herewith contain “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995. In general, forward-looking statements usually use words such as “may,” “believe,” “expect,” “anticipate,” “intend,” “should,” “plan,” “estimate,” “predict,” “continue” and “potential” or the negative of these terms or other comparable terminology, including statements related to the expected timing of the closing of the proposed merger with Grand River, the expected returns and other benefits of the proposed merger to shareholders, expected improvement in operating efficiency resulting from the proposed merger, estimated expense reductions resulting from the transactions and the timing of achievement of such reductions, the expected impact on and timing of the recovery of the impact on tangible book value, and the expected effect of the proposed merger on Isabella’s capital ratios. Forward-looking statements represent management’s beliefs, based upon information available at the time the statements are made, with regard to the matters addressed; they are not guarantees of future performance. Forward-looking statements are subject to numerous assumptions, risks and uncertainties that change over time and could cause actual results or financial condition to differ materially from those expressed in or implied by such statements.

Factors that could cause or contribute to such differences include, but are not limited to (1) the risk that the cost savings and any revenue synergies from the proposed merger may not be realized or take longer than anticipated to be realized, (2) disruption from the proposed merger with customers, suppliers, employee or other business partners, (3) the occurrence of any event, change or other circumstances that could give rise to the termination of the merger agreement, (4) the risk of successful integration of Grand River’s business into Isabella, (5) the failure to obtain the necessary approval by the shareholders of Grand River, (6) the amount of the costs, fees, expenses and charges related to the proposed merger, (7) the ability of the parties to obtain required governmental approvals of the proposed merger, (8) reputational risk and the reaction of each of the companies’ customers, suppliers, employees or other business partners to the merger, (9) the failure of the closing conditions in the Merger Agreement to be satisfied, or any unexpected delay in closing of the proposed merger, (10) the risk that the integration of Grand River’s operations into the operations of Isabella will be materially delayed or will be more costly or difficult than expected, (11) the possibility that the proposed merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events, (12) the dilution caused by Isabella’s issuance of additional shares of its common stock in the merger transaction, and (13) general competitive, economic, political and market conditions. Other relevant risk factors may be detailed from time to time in Isabella’s press releases and filings with the Securities and Exchange Commission (the “SEC”). Consequently, no forward-looking statement can be guaranteed. Neither Isabella nor Grand River undertakes any obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. For any forward-looking statements made in this communication or any related documents, Isabella and Grand River claim protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

Additional Information and Where to Find It

This communication is being made with respect to the proposed merger involving Isabella and Grand River. This material is not a solicitation of any vote or approval of the Grand River shareholders and is not a substitute for the proxy statement/prospectus or any other documents that Isabella and Grand River may send to their respective shareholders in connection with the proposed merger.

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval with respect to the proposed transaction. No offer of securities shall be made except by means of a prospectus meeting the requirements of the Securities Act of 1933, as amended, and no offer to sell or solicitation of an offer to buy shall be made in any jurisdiction in which such offer or solicitation would be unlawful.

In connection with the proposed merger, Isabella will file with the SEC a registration statement on Form S-4 that will include a proxy statement of Grand River and a prospectus of Isabella, as well as other relevant documents concerning the proposed transaction. BEFORE MAKING ANY VOTING OR INVESTMENT DECISIONS, WE URGE INVESTORS AND SECURITY HOLDERS TO READ THE REGISTRATION STATEMENT ON FORM S-4, THE PROXY STATEMENT/PROSPECTUS INCLUDED WITHIN THE REGISTRATION STATEMENT ON FORM S-4 AND ANY OTHER RELEVANT DOCUMENTS TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED MERGER BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT ISABELLA, GRAND RIVER AND THE PROPOSED MERGER. When final, the proxy statement/prospectus will be sent to the shareholders of Grand River seeking the required shareholder approval. Shareholders are also urged to carefully review and consider Isabella's public filings with the SEC, including, but not limited to, its proxy statements, its Annual Reports on Form 10-K, its Quarterly Reports on Form 10-Q, and its Current Reports on Form 8-K. Investors and security holders will be able to obtain free copies of the registration statement on Form S-4 and the related proxy statement/prospectus, when filed, as well as other documents filed with the SEC by Isabella through the web site maintained by the SEC at www.sec.gov. Documents filed with the SEC by Isabella will also be available free of charge on the Investor Relations page of Isabella’s website at https://ir.isabellabank.com/sec-filings/sec-filings/default.aspx.

Participants in Solicitation

Grand River, Isabella, and certain of their respective directors, executive officers and employees may be deemed to be participants in the solicitation of proxies of Grand River’s shareholders in respect of the proposed transaction under the rules of the SEC. Information regarding Isabella’s directors and executive officers is available in its definitive proxy statement related to its 2026 annual meeting of shareholders, which was filed with the SEC on March 23, 2026 and certain other documents filed by Isabella with the SEC. Other information regarding the participants in the solicitation of proxies in respect of the proposed transaction and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the proxy statement/prospectus and other relevant materials to be filed with the SEC. Free copies of these documents, when available, may be obtained as described in the preceding paragraph. Investors should read the proxy statement/prospectus carefully when it becomes available before making any voting or investment decisions.

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.

ISABELLA BANK CORPORATION

Dated:

June 12, 2026

By:

/s/ Gerald J. Ritzert

Gerald J. Ritzert

Chief Financial Officer

Isabella Bank Corporation filed SEC Form 8-K: Regulation FD Disclosure, Financial Statements and Exhibits