The disclosure is directed to a system, method, and computer program for dynamically identify a merchant associated with an authorization request for a payment card, wherein a merchant identifier in the authorization request is unrecognized. A plurality of unique signatures is created for each of a plurality of registered merchants, wherein the signatures for each registered merchant are based on values of merchant attributes associated with the registered merchant. In response to the system receiving an authorization request for a payment card that includes an unrecognized merchant identifier used to process authorization requests, a plurality of unique signatures is generated for the unrecognized merchant based on a combination of merchant attributes in the authorization request. A payment processing system then determines if the signatures match one of the signatures previously created for the registered merchants. If so, the authorization request is identified as originating from the matching registered merchant.