NB Bancorp, Inc. 10-Q

Item 5. Other Information N o n e . Item 6. Exhibits 31.1 Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 ​ ​ 31.2 Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 ​ ​ 32 Certification of Chief Executive Officer and Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 ​ ​ 101.INS XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document. ​ ​ 101.SCH Inline XBRL Taxonomy Extension Schema Document ​ ​ 101.CAL Inline XBRL Taxonomy Extension Calculation Linkbase Document ​ ​ 101.DEF Inline XBRL Taxonomy Extension Definition Linkbase Document ​ ​ 101.LAB Inline XBRL Taxonomy Extension Label Linkbase Document ​ ​ 101.PRE Inline XBRL Taxonomy Extension Presentation Linkbase Document ​ ​ Exhibit 104 Cover Page Interactive Data File - The cover page interactive data file does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document and contained in Exhibit 101 ​ ​ ​ ​ 56 Table of Contents SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. ​ ​ ​ NB BANCORP, INC. ​ ​ Date: August 7, 2026 /s/ Joseph Campanelli ​ Joseph Campanelli ​ Chairman, President and Chief Executive Officer ​ ​ Date: August 7, 2026 /s/ Jean-Pierre Lapointe ​ Jean-Pierre Lapointe ​ Senior Executive Vice President and Chief Financial Officer ​ ​ ​ ​ ​ ​ ​ 57