Abstract: Provided herein is a method for monitoring message content processed over a payment processor for a cardholder using a rules engine computing device. The rules engine computing device is associated with the payment processor that maintains a transaction history database that includes records for a plurality of payment transactions, and each of the records including a payment account number (PAN), a merchant identifier, and a transaction amount. The method includes (i) receiving a message from a registration computing device indicating that the cardholder is enrolled in a transaction monitoring service; (ii) associating the at least one PAN with the transaction monitoring service; (iii) querying the transaction history database to retrieve records including the at least one PAN; (iv) identifying a subset of transactions from the retrieved records; and (v) transmitting a list of the identified subset of transactions to at least one of the cardholder and the registration computing device.