NBT BANCORP INC

To the Stockholders and Board of Directors

NBT Bancorp Inc.:

Opinion on the Consolidated Financial Statements

We have audited the accompanying consolidated balance sheets of NBT Bancorp Inc. and subsidiaries (the Company) as of December 31, 2025 and 2024, the related consolidated statements of income, comprehensive income (loss), changes in stockholders’ equity, and cash flows for each of the years in the three-year period ended December 31, 2025, and the related notes (collectively, the consolidated financial statements). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the years in the three-year period ended December 31, 2025, in conformity with U.S. generally accepted accounting principles.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission, and our report dated February 27, 2026 expressed an unqualified opinion on the effectiveness of the Company’s internal control over financial reporting.

Basis for Opinion

These consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on these consolidated financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matters

The critical audit matters communicated below are matters arising from the current period audit of the consolidated financial statements that were communicated or required to be communicated to the audit committee and that: (1) relate to accounts or disclosures that are material to the consolidated financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matters below, providing separate opinions on the critical audit matters or on the accounts or disclosures to which they relate.

Allowance for credit losses – loans evaluated on a collective basis

As discussed in Notes 1 and 6 to the consolidated financial statements, the Company’s allowance for credit losses on loans evaluated on a collective basis (the collective ACL on loans) was $138.0 million of a total allowance for credit losses of $138.0 million as of December 31, 2025. The collective ACL on loans includes the measure of expected credit losses on a collective (pooled) basis for class segments of loans that share similar risk characteristics. The Company uses a discounted cash flow methodology where the respective quantitative allowance for each segment is measured by comparing the amortized cost to the present value of expected principal, interest and recovery cash flows projected using an econometric, probability of default (PD) and loss given default (LGD) modeling methodology. The Company uses PD regression models to develop the PD, and LGD models to develop the LGD, using historical credit loss experience over the observation period for both the Company and segment-specific selected peers. The application of these models incorporates multiple weighted external economic forecasts for the economic variables over the reasonable and supportable forecast period. After the reasonable and supportable forecast period, the Company reverts to long-term average economic variables over a reversion period on a straight-line basis. Contractual cash flows over the contractual life of the loans are the basis for expected principal, interest and recovery cash flows, adjusted for modeled defaults, expected prepayments and curtailments, and discounted at the loan-level effective interest rate. After quantitative considerations, the Company applies additional qualitative adjustments, giving consideration to the effects of limitations inherent in the quantitative model, so that the collective ACL on loans is reflective of the estimate of lifetime losses that exist in the loan portfolio at the balance sheet date.

We identified the assessment of the collective ACL on loans as a critical audit matter. A high degree of audit effort, including specialized skills and knowledge, and subjective and complex auditor judgment was involved in the assessment of the collective ACL on loans due to significant measurement uncertainty. Specifically, the assessment encompassed the evaluation of the collective ACL on loans methodology, including the methods and models used to estimate (1) the PD and LGD and their significant assumptions including the external economic forecasts and economic variables, and the related weighting of the forecasts, the reasonable and supportable forecast periods, the composition of the peer group, and the observation period from which historical Company and peer experience was used, and (2) the qualitative adjustments and the significant assumptions, including the effects of limitations inherent in the quantitative model. The assessment also included an evaluation of the conceptual soundness and performance of the PD regression and LGD models. In addition, auditor judgment was required to evaluate the sufficiency of audit evidence obtained.

The following are the primary procedures we performed to address this critical audit matter. We evaluated the design and tested the operating effectiveness of certain internal controls related to the Company’s measurement of the collective ACL on loans estimate, including controls over the:

We evaluated the Company’s process to develop the collective ACL on loans estimate by testing certain sources of data, factors, and assumptions that the Company used, and considered the relevance and reliability of such data, factors, and assumptions. In addition, we involved credit risk professionals with specialized skills and knowledge, who assisted in:

We also assessed the sufficiency of the audit evidence obtained related to the collective ACL on loans estimate by evaluating the:

Fair value measurement of the acquired loans

As discussed in Note 3 to the consolidated financial statements, the Company acquired Evans Bancorp, Inc. (Evans) on May 2, 2025. The transaction was accounted for as a business combination using the acquisition method of accounting. Accordingly, assets acquired, liabilities assumed, and consideration paid for Evans were recorded at their fair values at the acquisition date, including the fair value of acquired loans of $1.67 billion. The fair value of acquired loans was determined using a discounted cash flow methodology applied on a pooled basis based on certain key valuation assumptions including prepayment speeds, probability of default (PD), loss given default (LGD), and discount rate.

We identified the assessment of the fair value measurement of the acquired loans as a critical audit matter. A high degree of audit effort, including specialized skills and knowledge, and subjective and complex auditor judgment was involved in the assessment due to significant measurement uncertainty. Specifically, the assessment of the fair value measurement encompassed the evaluation of certain key valuation assumptions including prepayment speeds, PD, LGD, and discount rate.

The following are the primary procedures we performed to address the critical audit matter. We evaluated the design and tested the operating effectiveness of certain internal controls over the Company’s fair value measurement process for acquired loans, including controls related to the determination of certain key valuation assumptions including prepayment speeds, PD, LGD, and discount rate. We involved valuation professionals with specialized skills and knowledge who assisted in developing an independent estimate of the fair value of the acquired loan portfolio, including developing independent assumptions utilizing market data for the prepayment speeds, PD, LGD, and discount rate and comparing the results to the Company’s fair value estimate.

/s/KPMG LLP

We have served as the Company’s auditor since 1987.

Albany, New York

February 27, 2026

Consolidated