A method and system for processing a financial transaction using a co-brand proprietary payment card through a multi-party payment card interchange network is provided. The method includes storing within a database a list of merchants participating in a co-brand program with the interchange network, receiving an authorization request for the transaction involving the co-brand payment card wherein the authorization request includes a merchant identifier, determining whether the transaction originated at one of the participating merchants by comparing the received merchant identifier to the list of participating merchants stored within the database, manipulating the authorization request to include a private label identifier when the transaction is determined to have originated at one of the participating merchants, and transmitting an authorization response from the interchange network to the acquirer. The authorization response includes the private label identifier and designates the transaction for processing as a private label transaction.