X0508 4 2026-01-29 0001624322 Business First Bancshares, Inc. BFST 0002021584 Carter Donald Chad 500 LAUREL STREET, SUITE 101 BATON ROUGE LA 70801 1 EVP, Correspondent Banking 0 COMMON STOCK 2026-01-29 4 S 0 3778 27.27 D 13863 D Restricted Stock Units 0.0000 Common Stock 6636 6636 D This transaction was executed in multiple trades at prices ranging from $27.27 to $27.28. The price reported above reflects the weighted average sales price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. Includes units of the employer stock fund through the issuer's 401(k) plan equivalent to 6,799 shares of common stock of the issuer. Includes 1,156 shares of unvested restricted stock granted on February 1, 2024, which will vest on March 31, 2026. Under the terms of the relevant restricted stock grants, the reported shares of unvested restricted stock are subject to forfeiture upon the occurrence of certain events. Includes: (a) 2,584 time-based restricted stock units granted on December 12, 2024, of which 1,272 shares will vest on December 12, 2026 and the remaining 1,312 shares will vest on December 12, 2027; and (b) 4,052 time-based restricted stock units granted to the reporting person on March 1, 2025, of which 1,337 shares will vest on March 1, 2026, 1,337 shares will vest on March 1, 2027, and the remaining 1,378 shares will vest on March 1, 2028. /s/ Heather Roemer, as attorney-in-fact for Donald Chad Carter 2026-01-30