Systems and methods for interchange rate processing are provided. An interchange rate processing computing device is configured to receive transaction messages from one or more acquiring banks. Each transaction message may contain transaction data corresponding to a payment card transaction. The interchange rate processing computing device may analyze the transaction data to identify one or more one or more transaction characteristics. Based on the transaction characteristics, the interchange rate processing computing device may identify a lowest valid interchange rate for the payment card transaction and determine a corresponding interchange rate designator. The interchange rate processing computing device may then generate an enhanced transaction message including the transaction data and the interchange rate designator and transmit the enhanced transaction message to a payment processor, issuing bank, or other entity in a payment processing network.