The payment gateway converts the message from XML to ISO 8583 or a variant message format (format understood by EFT Switches) and then forwards the transaction information to the payment processor used by the merchant's acquiring bank. The payment processor forwards the transaction information to the card association (I.e.: Visa/MasterCard/American Express). If an American Express or Discover Card was used, then the card association also acts as the issuing bank and directly provides a response of approved or declined to the payment gateway.