Abstract: A payment processing method comprising receiving, through a payment application running on a mobile device of a customer, QR code data from an optical scanning device of the mobile device, receiving a client transaction settlement request comprising the QR code data and a customer ID, and receiving a processor transaction settlement request comprising the Merchant ID, the POS Terminal ID, and a transaction amount. The method further comprises verifying the Merchant ID and POS Terminal ID are identical between the client transaction settlement request and processor transaction settlement request, combining the client transaction settlement request and processor transaction settlement request into a combined transaction settlement request comprising the Merchant ID, the transaction amount, and customer financial instrument information, and transmitting the combined transaction settlement request to a processor payment gateway, receiving a transaction result, and transmitting the transaction result.