A merchant server includes a payment gateway and a gateway database. The payment gateway receives payment information from a payment page. The payment gateway adjusts an amount to be paid to produce an adjusted amount to be paid. The payment gateway forwards the adjusted amount to a payment processing entity for payment approval. The database includes end user data accessible by an end user identifier generated by the payment gateway using selected items within the payment information. The amount to be paid is adjusted by the payment gateway based on end user data accessed from the gateway database.