The present invention relates to a method and system for accurately measuring mail piece thickness for the purpose of determining postage discount qualification of a mail piece to be placed in a mail tray for receiving the maximum postage discount. The system includes a device for measuring the thickness of said mail piece and a user interface for entering data representing at least one postal address and the measured mail piece thickness. The system further includes a data processing system for processing the mail piece in accordance with the set of address data and the mail piece thickness, to produce a set of mail piece data. The data processing system is coupled to the thickness measuring device and the user interface and includes a memory for storing the sets of data. The system further sorts the sets of mail piece database upon postal guidelines such that qualification of a mail piece can be determined. Output is provided for displaying the resulting mail piece identifier.