Patent ID: 8152067

Claim:
A reply mail piece comprising: a substrate, at least one time-dependent machine readable ink marking on the substrate including postal information encoded therein, wherein the at least one marking is a time-dependent machine readable ink marking that changes visible state after a first predetermined time period due to exposure of the at least one time dependent machine readable ink marking to air, wherein, during the first predetermined time period, the reply mail piece is recognized as authorized recipient paid reply mail via machine reading of the at least one time dependent machine readable ink marking; and after the first predetermined time period, the reply mail piece changes visible state and is no longer recognized as authorized recipient paid reply mail by machine reading of the at least one time dependent machine readable ink marking, and wherein the at least one time-dependent machine readable ink marking comprises a reactive ink and oxidizing agent, and wherein the reply mail is piece is able to be processed for mailing as authorized recipient paid reply mail during the first predetermined time period by machine reading the at least one time-dependent machine readable ink marking, but is unable to be processed for mailing as authorized recipient paid reply mail after the first predetermined time period by machine reading the at least one time-dependent machine readable ink marking.