Abstract: A system for applying corrective mailing labels to documents and the like wherein a plurality of labels are releasably carried in sequential fashion on an elongated flexible substrate. The system includes a label printing station, a label applying drum, and label stripper means including a stripper blade having a free end disposed adjacent the drum and about which the substrate is guided so as to undergo a relatively abrupt reversal in direction. A substrate tractor drive downstream from the stripper blade normally pulls the substrate under tension about the free end of the stripper blade to effect release of labels from the substrate for application to predetermined envelopes, the substrate tractor drive being selectively operable to create a substrate loop path immediately downstream from the free end of the stripper blade to prevent release of an incorrect label from the substrate.