The BatchDeduplicator is a program for regular doublet searches performed in address tables on a fixed schedule, in order to ensure the long-term quality of this data. Particularly repetitive advertising in the case of direct marketing and the unnecessary repeated maintenance of client and other address data can thus be avoided. Of course, this leads to a direct savings of costs. Furthermore, a doublet search between two tables can also take a list of customers who do not wish to receive marketing transmissions into consideration, which can save a lot of trouble. Fast, largely automated and thus easy to use comparison of address databases for double addresses. The postal address (error-tolerant matching), telephone number, email address, address or customer number and tax number can all serve as matching criteria.