AUBURN NATIONAL BANCORPORATION, INC

In addition to results presented in accordance with U.S. generally accepted accounting principles (GAAP), this quarterly report on Form 10-Q includes certain designated net interest income amounts presented on a tax-equivalent basis, a non-GAAP financial measure, including the presentation and calculation of our net interest margin and efficiency ratio. In the first quarter of 2026, we changed the presentation of net interest income on a tax-equivalent basis to account for tax-exempt interest income on municipal loans. Prior period amounts have been revised herein to conform with the current period presentation. These changes had no effect on the presentation of GAAP net interest income in current or prior periods.

The Company believes the presentation of net interest income on a tax-equivalent basis provides comparability of net interest income from both taxable and tax-exempt sources and facilitates comparability within the industry. Although the Company believes these non-GAAP financial measures enhance investors’ understanding of its business and performance, these non-GAAP financial measures should not be considered an alternative to GAAP. The reconciliations of these non-GAAP financial measures to their most directly comparable GAAP financial measures are presented below.