Abstract: A depository envelope printing apparatus prints transaction identifying characters on envelopes deposited into an ATM, which envelopes may be of uneven contour as a result of their containing coins or folded notes or instruments. The apparatus includes a print head (120) and a tracking shoe (121) mounted on a carriage plate (110). The carriage plate is floatably mounted inside the ATM such that the tracking shoe tracks a depository envelope surface which is to accept printing as the envelope is being moved from the ATM customer to a place of storage within the ATM by a transport mechanism. The movements of the tracking shoe are transmitted to the print head so that it follows the contour of the envelope while printing is performed thereon. A probe located ahead of the tracking shoe in the direction of the envelope path tracks the level of the envelope surface a distance in advance of the tracking shoe.