Otherwise [e.g.: MasterCard or Visa card was used], the card association routes the transaction to the correct card issuing bank. The credit card issuing bank receives the authorization request, verifies the credit or debit available and then sends a response back to the processor (via the same process as the request for authorization) with a response code (I.e.:: approved, denied). In addition to communicating the fate of the authorization request, the response code is also used to define the reason why the transaction failed (I.e.: insufficient funds, or bank link not available).