A Master's License, or Master's Ticket, was a document required to be possessed by civilians operating space vessels. In 2266, interstellar criminal Harcourt Fenton Mudd was charged by Starfleet captain James Kirk with operating a vessel without a Master's License. Despite Mudd's claim that he did, in fact, possess one, the ship's computer verified that it was revoked on stardate 1116.4. (TOS: "Mudd's Women" )