A computer-implemented method of detecting associated payment devices comprises: receiving, by a processor from a payment network, transaction data representing a plurality of transaction records, a transaction amount, a transaction time, a terminal identifier, and a result code indicating success or failure of a transaction; identifying from said transaction records a declined transaction associated with a first payment device identifier, and determining a terminal identifier and transaction amount associated with the declined transaction; identifying from said transaction records a subsequent transaction occurring within a predetermined window of the declined transaction, the subsequent transaction being associated with the same terminal identifier and the same transaction amount as the declined transaction, the subsequent transaction being associated with a second payment device identifier that is different from the first payment device identifier; and storing, in a database, an association between the second payment device identifier and the first payment device identifier.