A method for automatic balancing of mail processing accounts for an inserter system that can automatically account for discrepancies in large quantities of gathered postage data, as well as conserving computer processing work. Mail pieces are formed on an inserter machine including a postage meter. The inserter control system gathers postage setting information and register information from the postage meter while forming mail pieces and provides it to an operating management system. It is understood that the gathered register information is potentially incomplete, out of chronological order, or from multiple sources, thereby creating the need for automatic balancing. The method defines mail piece blocks based on gathered register information and postage setting information. The definition includes assigning individual mail pieces to mail piece blocks based on a comparison of the starting register information for the particular mail piece as a function of the ending register information of a prior mail piece. If the comparison is consistent with processing of a single mail piece, then the particular mail piece is assigned to a same mail piece block as an immediate prior mail piece, and otherwise assigning the particular mail piece to a new mail piece block. Once mail piece blocks are defined, the process identifies gaps between defined mail piece blocks and mail pieces within the gaps. Finally, the mail pieces within the gaps are accounted for, and corrections are made, in accordance with a predetermined algorithm.