A system and corresponding method for detecting duplicate indicia on mailpieces. The system includes: a plurality of postal machines, each operated by a particular branch postal facility among a plurality of branch postal facilities, each postal machine having a scanning system for scanning indicia, each responsive to selection criteria, and each for providing data from sampled indicia based on the selection criteria and also for providing results of local verification of indicia; the plurality of branch postal facilities, each operating at least one of the postal machines, each responsive to selection criteria received from a central postal site, and in turn for providing the selection criteria to at least one of the postal machines it operates, each further responsive to the sampled indicia and to the local verification results provided by the postal machines it operates, and each for further providing to the central postal site data from the sampled indicia as well as a summary of all of the local verification results received from the postal machines it operates; and the central postal site, responsive to the sampled indicia and to the summary of the local verification results provided by each branch postal facility, for determining a duplicate detection list based on the sampled indicia, and for generating selection criteria to replace existing selection criteria and providing the selection criteria to the branch postal facilities so as to control sampling by the branch postal facilities by restricting the sampling to a subset that is a fraction of all indicia.