Abstract: A method for processing financial transactions includes transmitting an authorization request to a payment processing gateway server. The authorization request includes a supplemental header having a contract identification field that stores an identification of a contract between a merchant and a payment provider. A transaction response transmission is received from the payment processing gateway server in response to the authorization request. The transaction response transmission includes a transaction response header and a response data component. The transaction response header includes identification of a particular transaction to which the transaction response transmission is applicable. The response data component includes an indication that the contract is invalid. The indication that the contract is invalid is responded to by facilitating a rejection of the financial transaction.

Abstract: A gateway server, point of sale device and protocol are provided for processing financial transactions. A public network interface is configured to couple to a public network and communicate financial authorization requests. The financial authorization requests can include, for example, transaction specific data, a merchant store or location invariant and a supplemental header. A gateway processor processes the financial transaction authorization requests and couples to a financial network interface configured to couple to at least one financial network. The gateway provides a response to the point of sale device based upon data received from the financial network and the authorization request.