unauthorized completion.Commercial law. The act of filling in missing information in a negotiable instrument either without any authority to do so or beyond the authority granted. • Unauthorized completion is a personal defense, so it can be raised against any later holder of the instrument who does not have the rights of a holder in due course. See personal defense under DEFENSE(4). [Cases: Bills and Notes  60, 378, 452(1). C.J.S. Bills and Notes; Letters of Credit §§ 32–33, 36, 65, 74, 102, 197, 244–248, 260–261.]
[Blacks Law 8th]