A method of, and system for, processing payment for a transaction is provided. The method includes providing a user with an option to select payment for the transaction from an account associated with a communication line via which an electronic terminal is connected to a communication network. The communication line is typically a subscriber line and, accordingly, the account is a telephone account associated with the subscriber line. When a user transacts with a vendor for goods and/or services, the user may request to process payment using the telephone account instead of using a credit or debit card. The method includes investigating data using the telephone number associated with the subscriber line and, selectively approving the transaction dependent upon an outcome of the investigation. The invention extends to a transaction processor interface and to and a transaction validation module. The invention also extends to computer program products including the invention.