ISABELLA BANK CORP

INTERIM CONDENSED CONSOLIDATED BALANCE SHEETS

INTERIM CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

INTERIM CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED)

(1) See “Note 6 – Capital Ratios and Shareholders' Equity” of these consolidated financial statements for tax effect reconciliation.

INTERIM CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY (UNAUDITED)

INTERIM CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

NOTES TO INTERIM CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

Note 1 –Significant Accounting Policies

Basis of Presentation and Consolidation

The consolidated financial statements include the accounts of Isabella Bank Corporation, a registered financial holding company, and its wholly owned banking subsidiary, Isabella Bank. All intercompany balances and accounts have been eliminated in consolidation. References to “we,” “our,” “us,” and “the Corporation” refer to Isabella Bank Corporation, a Michigan corporation and registered financial holding company, our wholly-owned banking subsidiary, Isabella Bank, and our other consolidated subsidiaries. References to “the Bank” refer to Isabella Bank.

The accompanying unaudited interim condensed consolidated financial statements in this Form 10-Q have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In our opinion, all adjustments considered necessary for a fair presentation have been included. Operating results for the three and nine month periods ended September 30, 2026 are not necessarily indicative of the results that may be expected for the year ending December 31, 2026. For further information, refer to our Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the SEC on March 13, 2026 (the “2025 Annual Report on Form 10-K”).

Recent Developments

On June 16, 2026, the Corporation and the Bank entered into an equity distribution agreement with Piper Sandler & Co., as sales agent, pursuant to which the Corporation may offer and sell, from time to time, shares of its common stock with an aggregate gross sales price of up to $30.0 million, including through “at-the-market” offerings and other permitted methods. The sales agent is entitled to a commission of up to 3.0% of the gross sales price of the common stock sold in such offering. The Corporation is not obligated to sell any shares of its common stock pursuant to the equity distribution agreement, and may suspend or terminate sales thereunder at any time. Any shares sold will be issued pursuant to the Corporation’s effective shelf registration statement on Form S-3 and related prospectus supplement, and net proceeds, if any, are expected to be used for general corporate purposes, which may include, without limitation, contribution to the capital of the Bank to support its lending activities and growth. Please see Note 5 below for additional information about the at-the-market offering.

As previously disclosed, on June 11, 2026, the Corporation, 401 Merger Sub, Inc., a Michigan corporation and a wholly owned subsidiary of the Corporation (“Merger Sub”), and Grand River Commerce, Inc. (“Grand River”), entered into an Agreement and Plan of Merger (the “Merger Agreement”), providing for the merger of Merger Sub with and into Grand River, with Grand River as the surviving entity, immediately followed by the merger of Grand River with and into the Corporation, with the Corporation as the surviving entity. Refer to Note 9 below for additional information.

Identification and Classification of Merger-Related Expenses

Merger-related expenses are costs incurred directly in connection with merger and acquisition activities and are expensed in the period in which the costs are incurred and services are received. The costs to issue equity securities associated with the Merger are netted against the value of the securities issued. Merger-related expenses are expected to include legal fees for negotiation and drafting of merger agreements, accounting and auditing fees related to due diligence and financial statement preparation, consulting fees for strategic advisory services specific to the merger, costs related to regulatory filings and compliance, expenses for integration planning and execution (including IT, systems integration, and contract terminations), severance and retention bonuses for employees affected by the Merger, and travel and accommodation expenses directly related to merger activities. Merger-related expenses of $672,000 and $1.2 million recognized in the three and nine month periods ended September 30, 2026, respectively, primarily include investment banking, consulting, and legal fees.

Operating Segments

Segment information is prepared on the same basis that our Chief Executive Officer, who is our Chief Operating Decision Maker (“CODM”), manages our segments, evaluates financial results, and makes key operating decisions. While the CODM monitors the revenue streams of our various products and services, operations are managed, and financial performance is evaluated on a corporate-wide basis. Operating segments are aggregated intoone as operating results for all segments are similar. Accordingly, all of the banking-related operations are considered by management to be aggregated inone reportable operating segment.

The segment is also distinguished by the level of information provided to the CODM, who uses such information to review performance of various components of the business, which are then aggregated if operating performance, products and services, and geographical regions are similar. The CODM will evaluate the financial performance of our business components by evaluating revenue streams, significant expenses, and budget to actual results in assessing our reportable segment and in the determination of allocating resources. Further, the CODM uses revenue streams to evaluate product pricing and significant expenses to assess performance and evaluate return on assets.

Consolidated net income is used to benchmark our results against our competitors. Benchmarking and monitoring of budget to actual results are used in assessing performance and in establishing compensation. Revenue from banking operations consists primarily of loan and investment interest, deposit related fees, and wealth fees. Interest expense, provision for credit losses, compensation, and occupancy and equipment costs provide the significant expenses in our banking operations. All operations are domestic.

Changes in Significant Accounting Policies

Our accounting policies are materially the same as those discussed in Note 1 to the Consolidated Financial Statements included in our 2025 Annual Report on Form 10-K.

Subsequent Events

We evaluated subsequent events after September 30, 2026 through the date our interim condensed consolidated financial statements were issued for potential recognition and disclosure. Management determined that no subsequent events require financial statement recognition or disclosure between September 30, 2026 and the date our interim condensed consolidated financial statements were issued.

Pending Accounting Standards

ASU No. 2024-03: “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses”

In November 2024, ASU No. 2024-03 was issued to improve the disclosures about a public business entity’s expenses and address requests from investors for more detailed information about the types of expenses (including purchases of inventory, employee compensation, depreciation, amortization, and depletion) in commonly presented expense captions (such as cost of sales, selling general and administrative expense, and research and development). The new authoritative guidance is effective for annual periods beginning after December 15, 2026, and interim periods within annual reporting periods beginning after December 15, 2027, as clarified in ASU No. 2025-01 issued in January 2025. The new authoritative guidance under ASU No. 2024-03 is not expected to have a significant impact on our operations or financial statement disclosures.

ASU No. 2025-08: “Financial Instruments-Credit Losses (Topic 326): Purchased Loans”

In November 2025, ASU No. 2025-08 was issued to improve the decision usefulness of the financial reporting for acquired financial assets. Under the updated guidance, purchased seasoned loans are accounted for using the gross-up approach, which enhances comparability and consistency between organizations. The new authoritative guidance is effective for annual periods beginning after December 15, 2026, and interim periods within those annual reporting periods. Early adoption is permitted. We intend to early adopt this standard in conjunction with our pending acquisition which is expected to close in the fourth quarter of 2026.

Note 2 –AFS Securities

The amortized cost and fair value of AFS securities, with gross unrealized gains and losses, are as follows as of the dates indicated:

We made an accounting policy election to exclude accrued interest receivable on AFS securities from the amortized cost basis of AFS securities, as displayed above. Accrued interest receivable on AFS securities was $1.8 million and $1.7 million at September 30, 2026 and December 31, 2025, respectively, which is included in other assets on the consolidated balance sheets. Additional policy information related to AFS securities is discussed in detail in Note 1 to the Consolidated Financial Statements included in our 2025 Annual Report on Form 10-K.

The amortized cost and fair value of AFS securities by contractual maturity as of September 30, 2026 are as follows:

Expected maturities for government sponsored enterprises and states and political subdivisions may differ from contractual maturities as issuers may have the right to call or prepay obligations.

As the auction rate money market preferred investments have continual call dates, they are not reported by a specific maturity group. Because of their variable monthly payments, agency mortgage-backed securities and collateralized mortgage obligations are not reported by a specific maturity group.

The information in the following tables pertains to AFS securities with gross unrealized losses as of September 30, 2026 and December 31, 2025, aggregated by investment category and length of time that individual securities have been in a continuous loss position for which an ACL has not been recorded.

As of September 30, 2026, no ACL has been recognized on AFS securities in an unrealized loss position, as management does not believe any of the AFS securities are impaired due to reasons of credit quality. This is based on our analysis of the underlying risk characteristics, including credit ratings, and other qualitative factors related to our AFS securities and consideration of our historical credit loss experience and internal forecasts. The issuers of these securities continue to make timely principal and interest payments under the contractual terms of the securities. Management does not currently intend to sell any of the AFS securities reflected in the table above and believes it is more likely than not that we will not have to sell any such securities before a recovery of cost. Unrealized losses are generally due to a continued elevated market interest rate environment compared to the yields available at the time the underlying securities were purchased. The fair value is expected to recover as the securities approach their respective maturity date or repricing date, or if the market yields for such investments decline.

Note 3 –Loans and ACL

Loan Composition

The following table provides a detailed listing of our loan portfolio, excluding loans HFS, as of the dates indicated:

We originate commercial, agricultural, residential real estate, and consumer loans to customers primarily in Bay, Clare, Gratiot, Isabella, Mecosta, Midland, Montcalm, and Saginaw counties in Michigan. The ability of borrowers to fulfill their repayment obligations is often dependent upon the real estate, agricultural, manufacturing, retail, gaming, tourism, health care, higher education, and general economic conditions of this region. Substantially all of our consumer and residential real estate loans are secured by various items of property, while commercial loans are secured primarily by real estate, business assets, and personal guarantees. A portion of loans are unsecured.

Loans that we have the intent and ability to hold in our portfolio are reported at their outstanding principal balance adjusted for any charge-offs, the ACL, and deferred fees or costs. Unless a loan has a nonaccrual status, interest income is accrued over the term of the loan based on the principal amount outstanding. We made an accounting policy election to exclude accrued interest receivable on loans from the amortized cost basis of loans. Accrued interest receivable on loans was $6.8 million and $6.7 million at September 30, 2026 and December 31, 2025, respectively, which is included in other assets on the consolidated balance sheets. Loan origination fees and certain direct loan origination costs are capitalized and recognized as a component of interest income over the term of the loan using the interest method. Net unamortized deferred loan costs were $2.9 million and $3.0 million as of September 30, 2026 and December 31, 2025, respectively.

Commercial and agricultural loans include loans for commercial real estate, commercial operating loans, advances to mortgage brokers, farmland and agricultural production, and loans to states and political subdivisions. Repayment of these loans is dependent upon the successful operation and management of a business. We minimize our risk by limiting the amount of direct credit exposure to any one borrower to $18.0 million. Borrowers with direct credit needs of more than $18.0 million may be serviced through the use of loan participations with other commercial banks. Commercial and agricultural real estate loans commonly require loan-to-value limits of 80% or less. Depending upon the type of loan, past credit history, and current operating results, we may require the borrower to pledge accounts receivable, inventory, property, or equipment. Government agency guarantees may be required. Personal guarantees and/or life insurance beneficiary assignments are generally required from the owners of closely held corporations, partnerships, and sole proprietorships. In addition, we may require annual financial statements, prepare cash flow analyses, and review credit reports of our borrowers.

We offer adjustable-rate mortgages, construction loans, and fixed rate residential real estate loans which have amortization periods up to a maximum of 30 years. We consider the anticipated direction of interest rates, balance sheet duration, the sensitivity of our balance sheet to changes in interest rates, our liquidity needs, and overall loan demand to determine whether or not to sell fixed rate loans to Freddie Mac.

Our lending policies generally limit the maximum loan-to-value ratio on residential real estate loans to 100% of the lower of the appraised value of the property or the purchase price. Private mortgage insurance is typically required on loans with loan-to-value ratios in excess of 80% unless the loan qualifies for government guarantees.

Underwriting criteria for originated residential real estate loans generally include:

•Evaluation of the borrower’s ability to make monthly payments.

•Evaluation of the value of the property securing the loan.

•Ensuring the payment of principal, interest, taxes, and hazard insurance generally does not exceed 28% of a borrower’s gross income.

•Ensuring all debt servicing does not exceed 40% of income.

•Verification of acceptable credit reports.

•Verification of employment, income, and financial information.

Appraisals are performed by independent appraisers and are reviewed for appropriateness. Generally, mortgage loan requests are reviewed by our mortgage loan committee or through a secondary market underwriting system. Loans in excess of $1.5 million require the approval of one or more of the following Bank committees: Internal Loan Committee, the Executive Loan Committee, or the Board of Directors.

Consumer loans include secured and unsecured personal loans. Loans are amortized for a period of up to 15 years based on the age and value of the underlying collateral. The underwriting emphasis is on a borrower’s perceived intent and ability to pay rather than collateral value. No consumer loans are sold to the secondary market.

Nonaccrual and Past Due Loans

Nonaccrual loan policies, including a description of nonaccrual loans, are discussed in detail in Note 1 and Note 3 to the Consolidated Financial Statements included in our 2025 Annual Report on Form 10-K. There have been no material changes to these policies in the first nine months of 2026. The following table summarizes nonaccrual loan data by class of loans as of the dates indicated:

The following tables summarize the past due and current loans for the entire loan portfolio as of the dates indicated:

Credit Quality Ratings and Indicators

We have certain lending policies and procedures in place designed to maximize loan income within an acceptable level of risk. The Board of Directors reviews and approves these policies and procedures on a regular basis. A reporting system supplements the review process by providing management and the Board of Directors with frequent reports related to loan production, loan quality, and concentration of credit, loan delinquencies, nonperforming loans and potential problem loans. We seek to diversify the loan portfolio as a means of managing risk associated with fluctuations in economic conditions.

Internally assigned credit risk ratings are reviewed, at a minimum, when loans are renewed or when management has knowledge of improvements or deterioration of the credit quality of individual credits. Descriptions of the internally assigned credit risk ratings for commercial and agricultural loans are discussed in detail in Note 3 to the Consolidated Financial Statements included in our 2025 Annual Report on Form 10-K. There have been no material changes to the credit risk rating definitions in the first nine months of 2026.

The following tables display commercial and agricultural loans by credit risk ratings and year of origination as of the dates indicated:

Our primary credit quality indicator for residential real estate and consumer loans is the individual loan’s past due status. The following tables display loans by payment status and year of origination as of the dates indicated:

Loan Modifications to Borrowers Experiencing Financial Difficulty

We work with borrowers who are experiencing financial difficulty to identify mutually beneficial solutions that provide terms outside of normal lending practices to the borrowers while mitigating the risk of loss on the loans.

Typical modifications granted include, but are not limited to:

•Agreeing to interest rates below prevailing market rates for debt with similar risk characteristics.

•Extending the maturity date or amortization period beyond typical lending guidelines for loans with similar risk characteristics.

•Agreeing to an interest-only payment structure, delaying principal payments, or delaying payments.

•Forgiving principal.

To determine if a borrower is experiencing financial difficulty, factors we consider include:

•The borrower is currently in default on any debt.

•The borrower would likely default on any debt if the concession is not granted.

•The borrower’s cash flow is insufficient to service all debt if the concession is not granted.

•The borrower has declared, or is in the process of declaring, bankruptcy.

•The borrower is unlikely to continue as a going concern (if the entity is a business).

The following is a summary of the amortized cost basis of loan modifications granted to borrowers experiencing financial difficulty for the periods indicated:

We do not modify any loans by forgiving principal or accrued interest. We had committed to advance $3,000 and $221,000 in additional funds to be disbursed in connection with modified loans as of September 30, 2026 and December 31, 2025, respectively, as displayed in the tables above.

The following is a summary of the financial effect of the modifications granted to borrowers experiencing financial difficulty for the periods indicated:

We closely monitor the performance of loans that are modified to borrowers experiencing financial difficulty to understand the effectiveness of our modification efforts. The following tables summarize the amortized cost basis of loans that have been modified within the 12 months prior to the dates indicated:

The following table summarizes the amortized cost basis of loans that defaulted in the nine month period ended September 30, 2026 and were modified within 12 months prior to the default date. There wereno loans that defaulted in the three month period ended September 30, 2026 or in the three and nine month periods ended September 30, 2025 and were modified within 12 months prior to the default date. Modified loans, including those that have defaulted, are already included in the allowance for credit losses through the various methodologies used to estimate the allowance. As such, no modification to the allowance is recorded specifically due to a modified loan subsequently defaulting.

ACL - Loans

The credit quality of our loan portfolio is continuously monitored and is reflected within the ACL for loans. The ACL is an estimate of expected losses inherent within our loan portfolio. The ACL is adjusted by a credit loss expense, which is reported in earnings, and reduced by the charge-off of loan amounts, net of recoveries.

The ACL is evaluated on a regular basis for appropriateness. Our periodic review of the collectability of a loan considers historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, estimated value of any underlying collateral, and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available.

The primary factors behind the determination of the level of the ACL are specific allocations for loans individually evaluated, historical loss percentages, delinquency status, and other credit trends and risk characteristics, including current conditions and reasonable and supportable forecasts about the future. Determining the appropriateness of the allowance is complex and requires judgment by management about the effect of matters that are inherently uncertain. In future periods evaluations of the overall loan portfolio, in light of the factors and forecasts then prevailing, may result in significant changes in the allowance and credit loss expense in those future periods.

The methodology for estimating the amount of expected credit losses reported in the ACL is described within Note 3 to the Consolidated Financial Statements included in our 2025 Annual Report on Form 10-K. There have been no material changes to the ACL methodology in the first nine months of 2026.

A summary of activity in the ACL for loans, excluding unfunded commitments, by portfolio segment and the recorded investment in loans by segments follows for the periods indicated:

The following table illustrates the components of the ACL as of the dates indicated:

The following table presents loans that were evaluated for expected credit losses on an individual basis and the related specific allocations, by loan segment as of the dates indicated:

We have designated loans classified as collateral dependent for which we apply the practical expedient to measure the ACL based on the fair value of the collateral less cost to sell when the repayment is expected to be provided substantially by the sale or operation of the collateral and the borrower is experiencing financial difficulty. The fair value of the collateral is based on appraisals, which may be adjusted due to their age, and the type, location, and condition of the property or area or general market conditions to reflect the expected change in value between the effective date of the appraisal and the measurement date. Appraisals are updated every one to two years depending on the type of loan and the total exposure of the borrower. Loans evaluated for expected credit losses on an individual basis as of September 30, 2026 include $7.4 million in collateral dependent loans secured by commercial real estate and equipment, agricultural real estate and equipment, and residential real estate of $4.2 million, $2.4 million, and $826,000, respectively.

Note 4 –Borrowed Funds

Short-term borrowings

Short-term borrowings include securities sold under repurchase agreements without stated maturity dates, federal funds purchased, and FRB Discount Window advances, which all generally mature within one to three days from the transaction date.

A summary of short-term borrowed funds without stated maturity dates was as follows for the periods indicated:

Securities sold under agreements to repurchase are classified as secured borrowings and are reflected at the amount of cash received in connection with the transaction. The securities underlying the agreements had a carrying value and a fair value of $139.4 million and $87.8 million as of September 30, 2026 and December 31, 2025, respectively. Such securities remain under our control. We may be required to provide additional collateral based on changes to the fair value of underlying securities.

Securities sold under repurchase agreements without stated maturity dates were as follows as of the dates indicated:

We had pledged AFS securities and 1-4 family residential real estate loans in the following amounts as of the dates indicated:

AFS securities pledged to repurchase agreements consisted of the following as of the dates indicated:

AFS securities pledged to repurchase agreements are monitored to ensure the appropriate level is collateralized. In the event of maturities, calls, significant principal repayments, or significant decline in market values, we have an adequate level of AFS securities to pledge to satisfy collateral requirements.

As of September 30, 2026, we had the ability to borrow up to an additional $411.9 million without pledging additional collateral.

FHLB advances

FHLB advances are collateralized by a blanket lien on all qualified 1-4 family residential real estate loans, specific AFS securities, and FHLB stock.

The following table lists the maturities and weighted average interest rates of FHLB advances as of the dates indicated:

Subordinated notes

We have $30.0 million in aggregate principal amount of 3.25% Fixed-to-Floating Rate Subordinated Notes due 2031 (the “Notes”). The Notes initially had a fixed interest rate of 3.25% until June 15, 2026, after which time and until maturity on June 15, 2031, the interest rate will reset quarterly to an annual floating rate equal to the then-current 3-month SOFR plus 256 basis points. As of June 15, 2026, the Notes are redeemable by us at any time at our option, in whole or in part. The Notes are not subject to redemption at the option of the holders. Additionally, the Notes are intended to qualify for Tier 2 capital treatment, subject to regulatory limitations.

The following table summarizes our outstanding subordinated notes as of the dates indicated:

Note 5 –Computation of Earnings Per Common Share

Basic earnings per common share represents income available to common shareholders divided by the weighted average number of common shares outstanding during the period. Diluted earnings per common share includes additional common shares that would have been outstanding if dilutive potential common shares had been issued. Potential common shares that may be issued relate solely to outstanding shares in the Directors Plan, grant awards under the RSP, and purchase options under the ESPP.

Pursuant to the Corporation’s at-the-market offering, we issued and sold 322,685 shares of common stock during the nine months ended September 30, 2026, increasing equity by $12.5 million as of September 30, 2026.

Earnings per common share have been computed based on the following for the periods indicated:

Note 6 –Capital Ratios and Shareholders' Equity

As of September 30, 2026 and December 31, 2025, the most recent notifications from the FRB and the FDIC categorized us as “well capitalized” under the FDIC’s regulatory framework for prompt corrective action and the Basel III capital guidelines. To be categorized as “well capitalized,” an institution must maintain minimum total risk-based, Tier 1 risk-based, common equity Tier 1, and Tier 1 leverage ratios as set forth in the following tables. The minimum requirements presented below include the minimum required capital levels based on the Basel III capital guidelines. Capital requirements to be considered “well capitalized” are based upon the FDIC’s prompt corrective action regulations, as amended to reflect the changes under the Basel III capital guidelines. There were no conditions or events since the notifications that we believe have changed our categorizations. The following tables set forth these capital requirements and our ratios, both on a bank-only and on a consolidated basis, as of the dates indicated:

(1)“Well-capitalized” minimum Common Equity Tier 1 to Risk-Weighted and Leverage Ratio are not formally defined under applicable regulations for bank holding companies.

Total capital includes Tier 1 capital and Tier 2 capital. Tier 2 capital includes a permissible portion of the allowances for credit losses and outstanding subordinated debt, net of unamortized issuance costs. There are no significant regulatory constraints placed on our capital. As of September 30, 2026, the Bank exceeded all minimum Basel III risk-based capital requirements with the capital conservation buffer.

State banking regulations place certain restrictions on dividends paid by banks to their shareholders. Dividends paid by the Corporation’s bank subsidiary would be prohibited if the effect thereof would cause the bank subsidiary’s capital to be reduced below applicable minimum capital requirements.

The following table summarizes the changes in AOCI by component for the periods indicated:

Included in OCI for the three and nine month periods ended September 30, 2026 and 2025 are changes in unrealized gains and losses related to certain auction rate money market preferred stocks. These investments, for federal income tax purposes, have no deferred federal income taxes related to unrealized gains or losses given the nature of the investments.

A summary of the components of unrealized gains on AFS securities included in OCI follows for the periods indicated:

Note 7 –Revenue

Our revenue is comprised primarily of interest income, service charges and fees, gains on the sale of loans and AFS securities, earnings on corporate owned life insurance policies, and other noninterest income. Other noninterest income is typically service and performance driven in nature and comprised primarily of investment and trust advisory fees. We recognize revenue, excluding interest income, in accordance with ASC 606, Revenue From Contracts with Customers. Revenue is recognized when our performance obligation has been satisfied according to our contractual obligation.

We record receivables when revenue is unpaid and collectability is reasonably assured. Accounts receivable balances primarily represent amounts due from customers for which revenue has been recognized. Accounts receivable balances are recorded in the consolidated balance sheets in other assets. For the three and nine month periods ended September 30, 2026 and 2025, we satisfied all of our performance obligations pursuant to contracts with customers. As a result, we have not recorded any contract assets or liabilities. We estimate no returns or allowances for the three and nine month periods ended September 30, 2026 and 2025.

Our contracts with customers define our performance obligations with clearly established pricing which did not require us to allocate or disaggregate revenue by performance obligation. A summary of revenue recognized for each major category of contracts with customers, subject to ASC 606, is as follows for the periods indicated:

A significant portion of our revenue consists of interest income which is not subject to the requirements set forth in ASC 606.

Note 8 –Fair Value

Under fair value measurement and disclosure authoritative guidance, we group assets and liabilities measured at fair value into three levels, based on the markets in which the assets and liabilities are traded, and the reliability of the assumptions used to determine fair value, based on the prioritization of inputs in the valuation techniques. These levels are:

The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques maximize the use of observable inputs and minimize the use of unobservable inputs. Transfers between measurement levels are recognized at the end of reporting periods.

Fair value measurement requires the use of an exit price notion which may differ from entrance pricing. Generally, we believe our assets and liabilities classified as Level 1 or Level 2 approximate an exit price notion.

Following is a description of the valuation methodologies, key inputs, and an indication of the level of the fair value hierarchy in which the assets or liabilities are classified.

AFS securities: AFS securities are recorded at fair value on a recurring basis. Level 1 fair value measurement is based upon quoted prices for identical instruments. Level 2 fair value measurement is based upon quoted prices for similar instruments. If quoted prices are not available, fair values are measured using independent pricing models or other model-based valuation techniques such as the present value of future cash flows, adjusted for the security’s credit rating, prepayment assumptions and other factors such as credit loss and liquidity assumptions. The values for Level 1 and Level 2 investment securities are generally obtained from an independent third party. On a quarterly basis, we compare the values provided to alternative pricing sources.

Loans held for investment: We do not record loans at fair value on a recurring basis. However, some loans are individually evaluated for ACL purposes, and a specific ACL may be established. To measure reserve, the fair value of the loan is estimated using the fair value of the collateral, less costs to sell if foreclosure is probable, or the present value of expected future cash flows discounted at the loan’s effective interest rate. Loans not requiring an allowance represent loans for which the fair value of the expected repayments or collateral exceed the recorded investments in such loans.

We review the net realizable values of the underlying collateral for collateral dependent loans on at least a quarterly basis for all loan types. To determine the collateral value, we utilize independent appraisals, broker price opinions, or internal evaluations. We review these valuations to determine whether an additional discount should be applied given the age of market information that may have been considered as well as other factors such as costs to sell an asset if it is determined that the collateral will be liquidated in connection with the ultimate settlement of the loan. We use these valuations to determine if any specific reserves or charge-offs are necessary. We may obtain new valuations in certain circumstances, including when there has been significant deterioration in the condition of the collateral, if the foreclosure process has begun, or if the existing valuation is deemed to be outdated.

The following tables list the quantitative information about loans measured at fair value on a nonrecurring basis as of the dates indicated:

Collateral discount rates may have ranges to accommodate differences in the age of the independent appraisal, broker price opinion, or internal evaluation.

OMSR: OMSR (which are included in other assets) are subject to impairment testing. To test for impairment, we utilize a discounted cash flow analysis using interest rates and prepayment speed assumptions currently quoted for comparable instruments and discount rates. If the valuation model reflects a value less than the carrying value, OMSR are adjusted to fair value through a valuation allowance as determined by the model. As such, we classify OMSR subject to nonrecurring fair value adjustments as Level 3.

The following table lists the quantitative information about OMSR fair value measurement as of the dates indicated:

The preceding methods described may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Although we believe our valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement.

Estimated Fair Values of Financial Instruments Not Recorded at Fair Value in their Entirety on a Recurring Basis

Disclosure of the estimated fair values of financial instruments, which differ from carrying values, often requires the use of estimates. In cases where quoted market values in an active market are not available, we use present value techniques and other valuation methods to estimate the fair values of our financial instruments. These valuation methods require considerable judgment and the resulting estimates of fair value can be significantly affected by the assumptions made and methods used.

The carrying amount and estimated fair value of financial instruments not recorded at fair value in their entirety on a recurring basis were as follows as of the dates indicated:

(1) Due to the characteristics of FHLB stock and equity securities without readily determinable fair values, they are not disclosed under a specific fair value hierarchy. When an impairment or write-down related to these securities is recorded, such amount would be classified as a nonrecurring Level 3 fair value adjustment.

Financial Instruments Recorded at Fair Value

The table below presents the recorded amount of assets and liabilities measured at fair value on the dates indicated:

We recorded impairments related to OMSR of $1,000 and $3,000 through earnings for the three and nine month periods ended September 30, 2025, respectively. No impairments related to OMSR were recorded for the three and nine month periods ended September 30, 2026. We recorded impairments related to foreclosed assets of $26,000 and $89,000 for the three and nine month periods ended September 30, 2025, respectively. No impairments related to foreclosed assets were recorded for the three and nine month periods ended September 30, 2026. We had no other assets or liabilities recorded at fair value with changes in fair value recognized through earnings, on a recurring basis or nonrecurring basis, as of September 30, 2026. Further, we had no unrealized gains and losses included in OCI for recurring Level 3 fair value measurements held at the end of the reporting period.

Note 9 –Business Combinations

On June 11, 2026, the Corporation, 401 Merger Sub, Inc., a Michigan corporation and a wholly owned subsidiary of the Corporation (“Merger Sub”), and Grand River Commerce, Inc. (“Grand River”), entered into an Agreement and Plan of Merger (the “Merger Agreement”). The Merger Agreement provides that, upon the terms and subject to the conditions set forth therein, Merger Sub will merge with and into Grand River, with Grand River as the surviving entity (the “Merger”), and immediately following the Merger, Grand River will merge with and into the Corporation, with the Corporation as the surviving entity (the “Second Step Merger”). The Merger Agreement further provides that immediately following the Second Step Merger, Grand River Bank, a Michigan state-chartered member bank and wholly owned subsidiary of Grand River, will merge with and into the Bank, with the Bank as the surviving bank (the “Bank Merger” and, together with the Merger and the Second Step Merger, the “Transaction”). On October 6, 2026, we announced that we have received all required regulatory approvals to complete the Merger, that the Grand River shareholders approved the Merger on September 18, 2026, and that we expect the Merger to close on November 2, 2026, pending satisfaction or waiver of customary closing conditions.

Upon the terms and subject to the conditions of the Merger Agreement, at the effective time of the Merger (the “Effective Time”), each voting and non-voting share of common stock of Grand River (“Grand River Common Stock”) issued and outstanding immediately prior to the Effective Time, other than certain shares held by Grand River or the Corporation, will be converted into the right to receive, at the election of the holder thereof, and subject to adjustment and proration, as applicable, (i) an amount of cash equal to the quotient of (A) $18,262,391 (the “Aggregate Cash Consideration”), divided by (B) the product obtained by multiplying (x) the number of shares of Grand River Common Stock issued and outstanding as of the

Effective Time by (y)0.35 (the “Cash Conversion Number”), rounded to the nearest cent (the “Per Share Cash Consideration”), or (ii) the number of shares of common stock of the Corporation, no par value (“Isabella Common Stock”), multiplied by the Exchange Ratio (as defined below).

The Exchange Ratio is defined in the Merger Agreement as a number, as adjusted, of shares of Isabella Common Stock equal to the quotient of (A)839,003 shares of Isabella Common Stock, divided by (B) the difference of (1) the aggregate number of shares of Grand River Common Stock issued and outstanding immediately prior to the Effective Time, other than certain shares held by Grand River or the Corporation, minus (2) the Cash Conversion Number, rounded to the nearest ten thousandth (the “Per Share Stock Consideration”). The Per Share Cash Consideration and/or the Per Share Stock Consideration are sometimes referred to herein collectively as the “Merger Consideration.”

Merger Consideration elections by Grand River shareholders will be subject to proration procedures whereby 65% of the shares of Grand River Common Stock will be exchanged for the Per Share Stock Consideration and 35% of the shares of Grand River common stock will be exchanged for the Per Share Cash Consideration. Based on the assumption of 9,136,529 shares of Grand River Common Stock issued and outstanding as of the Effective Time, the Per Share Cash Consideration to be paid is estimated to be approximately $5.71 and the Exchange Ratio is estimated to be approximately 0.1413. At June 30, 2026, Grand River had approximately $508.7 million in total assets, $422.9 million in total loans and $445.5 million in total deposits. The pro forma company is projected to have approximately $2.7 billion in total assets.