In order to change the terms of an approved bond, both the principal and the surety company that guaranteed the bond must agree to the change. TTB must also approve the change. All changes to the terms of a bond must be executed on form TTB F 5000.18, Change of Bond (Consent of Surety) by both the principal and the surety with the same formality and proof of authority as required for the original bond. The completed, executed TTB F 5000.18 must be submitted to the National Revenue Center.