This Proxy Statement is furnished in connection with the solicitation of proxies, to be voted at our Annual Meeting of Shareholders (the “Annual Meeting”) which is to be held virtually, in lieu of an in-person meeting, on Tuesday, May 4, 20219, 2023 at 5:00 p.m., at the Courtyard by Marriott, 2400 East Campus Drive, Mt. Pleasant, Michigan, or at any adjournment or adjournments thereof, for the purposes set forth in the accompanying Notice of the Annual Meeting of Shareholders and in this Proxy Statement.

We have fixed the close of business on March 12, 202117, 2023 as the record date for the determination of shareholders entitled to notice of, and to vote at, the Annual Meeting and any adjournment or adjournments thereof. We have only one class of common stock and no preferred stock. As of March 12, 2021,17, 2023, there were 7,955,4987,561,422 shares of stock outstanding. Each outstanding share entitles the holder thereof to one vote on each separate matter presented for vote at the meeting. You may vote on matters that are properly presented at the Annual Meeting by attending the meeting and casting a vote, signing and returning the enclosed proxy, voting on the internet, or voting by phone. You may change your vote or revoke your proxy at any time before it is voted at the Annual Meeting by filing with theIsabella Bank Corporation (the “Corporation”) an instrument revoking it, filing a duly executed proxy bearing a later date (including a proxy given over the internet or by phone) or by attending the meeting and electing to vote in person. You are encouraged to vote by mail, internet, or phone.

A quorum must be present in order to hold the Annual Meeting. A quorum is present if a majority of the shares of common stock entitled to vote are represented in person or by proxy. If you execute and return a proxy, those shares will be counted to determine if there is a quorum, even if you abstain or fail to vote on any of the proposals.

At this year’s Annual Meeting, you will elect fourthree directors to serve for a term of three years. You may vote in favor or against, or abstain from votingwithhold your vote with respect to any or all nominees. Directors are elected by a plurality of the votes cast at the Annual Meeting. Abstentions and shares not voted, including broker non-votes, have no effect on the elections.

Except as otherwise specified, proxies will be voted for the election of the fourthree nominees. If a nominee becomes unable or unwilling to serve, proxies will be voted for such other person, if any, as shall be designated. However, we know of no reason to anticipate that this will occur. The four nominees who receive the greatest number of votes cast will be elected directors. Each of the nominees has agreed to serve as a director if elected.

Nominees and current directors, including their principal occupation for the last five or more years, age, and length of service as a director, are listed below.

Each nominee and current director possesses these qualities and provides a diverse complement of specific business skills and experience. In addition to the general qualifications described above, qualifications are included in the biographical summaries provided below.

a licensed real estate broker in Michigan and builder.Florida. He currently serves as a board member for the Central Michigan University Advancement Board, and is past board member of the Mt. Pleasant Area Community FoundationFoundation. Mr. McGuirk has expertise in business, and the Central Michigan University Advancement Board. It is because of Mr. McGuirk's business experience and hisa strong commitment to community involvement that Mr. McGuirk should serve on the Board.involvement.

Our Governance Policy provides that only directors who are deemed to be independent as set forth by the NASDAQ listing requirements and SEC rules are eligible to hold the office of chairperson. Additionally, the chairpersons of Board established committees must also be independent directors. It is our belief that having a separate chairperson and CEO best serves the interest of the shareholders. The Board elects its chairperson at the first Board meeting following the Annual Meeting. Independent members of the Board meet without inside directors at least twice per year.

Management is responsible for our day-to-day risk management and the Board’s role is to engage in informed oversight. The Board utilizes committees to oversee risks associated with compensation and governance. The Isabella Bank Board of Directors is responsible for overseeing credit, investment, information technology, interest rate, and trust risks. The chairpersons of the respective boards or committees report on their activities on a regular basis.

Our Audit Committee is responsible for overseeing the integrity of our consolidated financial statements, the independent auditors’ qualifications and independence, the performance of our internal audit function and those of independent auditors, our system of internal controls, our financial reporting and system of disclosure controls, and our compliance with legal and regulatory requirements and with our Code of Conduct and Business Ethics.

The Board met 1314 times during 2020.2022. No current member of the Board attended less than 75% of the aggregate meetings of the Board and all committees on which such director served during 2020.2022. The Board has an Audit Committee, a Nominating and Corporate Governance Committee, and a Compensation and Human Resource Committee.

In accordance with the provisions of the Sarbanes-Oxley Act of 2002, directordirectors Bourland and Payton met the requirements of Audit Committee Financial Expert and have been so designated. The Audit Committee also consists of directors Kleinhardt, Maness, (ex-officio),and Opperman and Payton (effective March 31, 2021)(ex-officio).

The Nominating and Corporate Governance Committee is responsible for evaluating and recommending individuals for nomination to the Board for approval. This Committee, in evaluating nominees, including incumbent directors and any nominees put forth by shareholders, considers business experience, skills, character, judgment, leadership experience, and their knowledge of the geographical markets, business segments or other criteria the Committee deems relevant and appropriate based on the current composition of the Board. This Committee considers diversity in identifying members with respect to our geographical markets served, the industry knowledge and experience of the nominee, and community relations of the nominee.

The Nominating and Corporate Governance Committee will consider, as potential nominees, persons recommended by shareholders. Recommendations should be submitted in writing to the Secretary of the Corporation, 401 N. Main St., Mt. Pleasant, Michigan 48858 and include the shareholder’s name, address and number of shares of the Corporation owned by the

Shareholders may communicate with the Board by sending written communications to the attention of the Corporation’s Secretary, Isabella Bank Corporation, 401 N. Main St., Mt. Pleasant, Michigan 48858. Communications will be forwarded to the Board or the appropriate committee, as soon as practicable.

The Audit Committee oversees the financial reporting process on behalf of the Board. The 20202022 Audit Committee consisted of directors Bourland, Kleinhardt, Maness, Opperman (ex-officio), and Opperman.*Payton.

The Audit Committee is responsible for pre-approving all auditing services and permitted non-audit services by our independent auditors, or any other auditing or accounting firm, if those fees are reasonably expected to exceed 5.0% of the current year agreed upon fee for independent audit services. The Audit Committee has established general guidelines for the permissible scope and nature of any permitted non-audit services in connection with its annual review of the audit plan and reviews the guidelines with the Board.

Management has the primary responsibility for the consolidated financial statements and the reporting process including the systems of internal controls. In fulfilling its oversight responsibilities, the Audit Committee reviewed the audited consolidated financial statements in the Annual Report with management including a discussion of the acceptability of the accounting principles, the reasonableness of significant judgments, and the clarity of disclosures in the consolidated financial statements. The Audit Committee also reviewed with management and the independent auditors, management’s assertion on the design and effectiveness of our internal control over financial reporting as of December 31, 2020.2022.

The Audit Committee reviewed with our independent auditors, who are responsible for expressing an opinion on the conformity of those audited consolidated financial statements with accounting principles generally accepted in the United States of America, their judgments as to the acceptability of our accounting principles and such other matters as are required to be discussed with the Audit Committee by the standards of the Public Company Accounting Oversight Board (United States) (“PCAOB”), including those described in Auditing Standard No. 1301, “Communications with Audit Committees”, as may be modified or supplemented. In addition, the Audit Committee has received the written disclosures and the letter from the independent auditors required by PCAOB Rule 3526, “Communication with Audit Committees Concerning Independence”, as may be modified or supplemented, and has discussed this issue with the independent auditors.

The Audit Committee discussed with our internal and independent auditors the overall scope and plans for their respective audits. The Audit Committee meets with the internal and external independent auditors, with and without management present, to discuss the results of their examinations, their evaluations of our internal controls, and the overall quality of our financial reporting process. The Audit Committee held sixfive meetings during 2020.2022.

In reliance on the reviews and discussions referred to above, the Audit Committee recommended to the Board of Directors (and the Board has approved) that the audited consolidated financial statements be included in the Annual Report on Form 10-K for the year ended December 31, 20202022 for filing with the Securities and Exchange Commission. The Audit Committee has appointed Rehmann Robson LLC as the independent auditors for the 20212023 audit.

Respectfully submitted,

Executive officers are compensated in accordance with their employment with the applicable entity. The following table shows information on compensation earned in each of the last two fiscal years ended December 31, 2020,2022, for the CEO, CFO, and our next most highly compensated executive officer.officer, collectively the named executive officers (“NEOs”).

Annual contributions are made to the plan as required by accepted actuarial principles, applicable federal tax laws, and to pay expenses related to operating and maintaining the plan. The amount of contributions on behalf of any one participant cannot be separately or individually computed.

Pension plan benefits are based on years of service and the employees’ five highest consecutive years of compensation out of the last ten years of service, through December 31, 2006.

A participant may earn a benefit for up to 35 years of accredited service. Earned benefits are 100% vested after five years of service. Benefit payments normally start when a participant reaches age 65. A participant with more than five years of service may elect to take early retirement benefits anytime after reaching age 55. Benefits payable under early retirement are reduced actuarially for each month prior to age 65 in which benefits begin.

Under the provisions of the plan, participants are eligible for early retirement after reaching the age of 55 with at least five years of service. The early retirement benefit amount is the accrued benefit payable at normal retirement date reduced by 5/9% for each of the first 60 months and 5/18% for each of the next 60 months that the benefit commencement date precedes the normal retirement date.

An initial amount was credited for each eligible employee as of January 1, 2007. Subsequent amounts have been credited on each allocation date thereafter as defined in the Retirement Bonus Plan. The amount of the initial allocation and the annual allocation shall be determined pursuant to the payment schedule adopted at our sole and exclusive discretion, as set forth in the Retirement Bonus Plan.

Under the provisions of the Retirement Bonus Plan, participants are eligible for early retirement upon attaining 55 years of age. There is no difference between the calculation of benefits payable upon early retirement and normal retirement; however, the participant would not receive their full benefit under early retirement.

Distribution of deferred fees from the Directors Plan occurs when the participant retires from the Board or upon the occurrence of certain other events. The participant is eligible to receive distributions in the form of shares of our common stock of all of the stock units that are then in his or her account, and any unconverted cash will be converted to and rounded up to a whole share of stock and distributed, as well. Any common stock issued from deferred fees under the Directors Plan will be considered restricted stock under the Securities Act of 1933, as amended. Common stock purchased through the DRIP Plan are not considered restricted stock under the Securities Act of 1933, as amended.

The SERP provides default terms that may be modified by a participant’s participation agreement, including default vesting, interest and payment terms. Under the SERP’s default vesting terms, a participant is initially unvested in the participant’s SERP account and becomes 100% vested upon attaining normal retirement age, retirement, involuntary separation from service without cause, death, disability or a change in control. Special vesting rules apply to amounts that are credited after a change in control. Under the SERP’s interest rule, a participant’s account balance is credited with interest annually, the rate of which may be changed and is based on Federated Investor's Institutional Money Market Management Fund yield (MMPXX) for the current plan year, updated annually. Under the SERP’s default payment terms, a participant’s vested and nonforfeited account balance will be paid in a single cash lump sum within 90 days after the first to occur of the participant’s separation from service (subject to a six-month delay for a “specified employee”), death, disability, or any date specified in the participant’s participation agreement. The SERP also includes restrictive covenants that restrict a participant’s ability to compete with us and certain other activities.

The estimated amounts payable to each named executive officer upon severance from employment, retirement, termination upon death or disability or termination following a change in control are described below. For all termination scenarios, the amounts assume such termination took place as of December 31, 2020.2022.

In the event of the retirement of an executive officer, the officer would receive the benefits identified above.

In the event of death or disability of an executive officer, in addition to the benefits listed above, the executive officer will also receive payments under our life insurance plan or under our disability plan as appropriate.

We currently do not have a change in control agreement with any of the executive officers. Under the SERP, each participant would become 100% vested in their SERP account upon a change in control. Under certain conditions, following a change in control, if a participant is involuntarily terminated without cause or voluntarily terminates for good reason all uncredited annual credits would be credited to his or her SERP account. If termination took place on December 31, 2020,2022, that would have resulted in an additional credit to Jae A. Evans’ SERP account of $135,000,$0, Neil M. McDonnell's SERP account of $212,500,$175,000, and Jerome E. Schwind's SERP account of $520,000$456,000 and a total credit for each individual of $837,211, $250,660,$837,800, $250,694, and $602,854,$602,926, respectively.

Under the RSP, each participant would become 100% vested in their RSP account upon a change in control. Under certain conditions, following a change in control, if a participant is involuntarily terminated without cause or voluntarily terminates for good reason all nonvested shares would be fully vested. If termination took place on December 31, 2020,2022, that would have resulted in vested shares to Jae A. Evans’ RSP account of 2,42710,427 ($42,500)329,236), Neil M. McDonnell's RSP account of 9524,136 ($16,673)131,130), and Jerome E. Schwind's RSP account of 1,2795,560 ($22,383)175,828).

We paid $1,500 per board meeting plus a retainer of $10,000 to each member during 2020.2022. Members of the Audit Committee were paid $750 per Audit Committee meeting attended. Members of the Nominating and Corporate Governance Committee were paid $350 per meeting attended. Members of the Compensation and Human Resource Committee were paid $350 per meeting attended. The chairperson of the Board is paid a retainer of $35,000, and the chairperson for the Audit Committee is paid a retainer of $6,000, and the vice chairperson for the Audit Committee is paid a retainer of $2,000.$6,000.

Under the Directors Plan, upon a participant’s retirement from the Board, or the occurrence of certain other events, the participant is eligible to receive a distribution in the form of shares of our common stock of all of the stock units that are then credited to the participant's account. The plan does not allow for cash settlement. Stock issued under the Directors Plan is restricted stock under the Securities Act of 1933, as amended.

We established a Rabbi Trust to supplement the Directors Plan. The Rabbi Trust is an irrevocable grantor trust to which we may contribute assets for the limited purpose of funding a nonqualified deferred compensation plan. Although we may not reach the assets of the Rabbi Trust for any purpose other than meeting itsour obligations under the Directors Plan, the assets of the Rabbi

We transferred $1,531,784$1,045,958 to the Rabbi Trust in 2020,2022, which held 59,162154,879 shares of our common stock for settlement as of December 31, 2020.2022. As of December 31, 2020,2022, there were 117,05352,961 stock units credited to participants’ accounts, whichaccounts; such credits are unfunded as of such date to the extent that they are in excess of the stock and cash that has been credited to the Rabbi Trust. All amounts are unsecured claims against our general assets. The net cost of this benefit was $198,119$219,374 in 2020.2022.

Certain directors and officers and members of their families were loan customers of the Bank, or have been directors or officers of corporations, members or managers of limited liability companies, or partners of partnerships which have had transactions with the Bank. In our opinion, all such transactions were made in the ordinary course of business and were substantially on the same terms, including collateral and interest rates, as those prevailing at the same time for comparable transactions with customers not related to the Bank. These transactions do not involve more than normal risk of collectability or present other unfavorable features. Total loans to these customers were approximately $2,977,000$20,963,000 and $3,695,000$22,558,000 as of December 31, 2020,2022 and 2019.2021.

The Audit Committee has appointed Rehmann Robson LLC as our independent auditors for the year ending December 31, 2021.

The audit fees were for performing the integrated audit of our consolidated annual financial statements and the internal control report related to the Federal Deposit Insurance Corporation Improvement Act, reviews of interim quarterly financial statements included in our Quarterly Reports on Form 10-Q, and services that are normally provided by Rehmann Robson LLC in connection with statutory and regulatory filings or engagements.

The audit related fees are typically for various discussions related to the adoption and interpretation of new accounting pronouncements. During 2020,2022, this included fees for procedures related to nonrecurring regulatory filings. Also included are fees for auditing of our employee benefit plans.

The tax fees were for the preparation of our state and federal income tax returns and for consultation on various tax matters. All other fees were training and consultant related services.

The Audit Committee has considered whether the services provided by Rehmann, Robson LLC, other than the audit fees, are compatible with maintaining Rehmann Robson LLC’sRehmann’s independence and believes that the other services provided are compatible.

All non-audit services to be performed by Rehmann Robson LLC must be approved in advance by the Audit Committee if those fees are reasonably expected to exceed 5.0% of the current year agreed upon fee for independent audit services, so long as such services were recognized by the Corporation at the time of engagement to be non-audit services, and such services are promptly brought to the attention of the Audit Committee subsequent to completion of the audit. As permitted by SEC rules, the Audit Committee has authorized its chairperson to pre-approve audit, audit-related, tax and non-audit services, provided that such approved service is reported to the full Audit Committee at its next meeting.

As early as practicable in each calendar year, the independent auditor provides to the Audit Committee a schedule of the audit and other services that the independent auditor expects to provide or may provide during the next twelve months. The schedule will be specific as to the nature of the proposed services, the proposed fees, timing, and other details that the Audit Committee may request. The Audit Committee will by resolution authorize or decline the proposed services. Upon approval, this schedule will serve as the budget for fees by specific activity or service for the next twelve months.

A schedule of additional services proposed to be provided by the independent auditor, or proposed revisions to services already approved, along with associated proposed fees, may be presented to the Audit Committee for their consideration and approval at any time. The schedule will be specific as to the nature of the proposed service, the proposed fee, and other details that the Audit Committee may request. The Audit Committee will by resolution authorize or decline authorization for each proposed new service.

Applicable SEC rules and regulations permit waiver of the pre-approval requirements for services other than audit, review or attest services if certain conditions are met. Out of the services characterized above as audit-related, tax and other professional services, none were billed pursuant to these provisions in 20202022 and 20192021 without pre-approval.

Any proposals which you intend to present at the next Annual Meeting must be received before November 26, 202128, 2023 to be considered for inclusion in our Proxy Statement and proxy for that meeting. Proposals should be made in accordance with Securities and Exchange Commission Rule 14a-8.

Our directors are encouraged to attend the Annual Meeting. At the 20202022 Annual Meeting, all directors, with the exception of Mr. Manifold,Kleinhardt, were in attendance.

We will bear the cost of soliciting proxies. In addition to solicitation by mail, officers and other employees may solicit proxies by telephone or in person, without compensation other than their regular compensation.

We do not intend to bring any other business before the meeting for action. However, if any other business should be presented for action, it is the intention of the persons named in the enclosed form of proxy to vote in accordance with their judgment on such business.