A method and system for enabling a mailer to sort incoming mail pieces in accordance with changeable criteria that are important to the mailer. This invention accomplishes the foregoing by placing a unique identifier or code tying the mail piece to a data file on each business reply envelope, on or in each windowed envelope or post card that is sent to a customer and returned to the mailer. The unique identifier would enable the mailer to establish parameters for evaluating the unique identifier so as to set a priority for processing mail that is in the mail stream, i.e. prioritize mail that is received just before a late fee is due to improve customer relations. The code tying the mail piece to a data file may be used by the mailer to track payment cycles, order the sortation of incoming mail based upon credit balances, process mail based upon the expected amount of the enclosed check. The foregoing would enable the mailer to receive monies earlier and improve the mailers cash flow.