Ownership Filing for Alfred V. Testa

This filing details the stock ownership of Alfred V. Testa, an EVP/President of Commercial Banking at NBT BancORP INC. As of May 19, 2026, Mr. Testa has indirect ownership of 2603.671 shares of NBT Bancorp Inc. Common Stock through a 401k plan and direct ownership of 5643 shares. The filing also includes Exhibit 24, a Power of Attorney document, appointing Annette Burns and Scott Kingsley as attorneys-in-fact to execute and file Forms 3, 4, and 5 on behalf of Mr. Testa, related to his reporting requirements under Section 16(a) of the Securities Exchange Act of 1934. This power of attorney remains effective until Mr. Testa is no longer required to file such forms or until it is revoked in writing.