A computer-based customer tracking system passively identifies customers. Acquired biometric identification information is sent to a computer processor, which searches files in a library for matching biometric data. If no match is found, the processor opens a new file in the library. If a match is found, said processor stores in the file that a repeat identification has occurred. If said processor is only able to reduce the number of possible matches to two or more files, personnel determines if a match certain has occurred. If prior activity information stored in the file exceeds a predetermined level, the prior activity information is retrieved from the file and sent to a terminal, preferably at the location of the transaction. New information from the transaction is stored for future access. A selected or assigned personal identification number (PIN) reduces the time associated with, and improves the efficiency of, the identification process.