Abstract: Methods and systems are described for processing transactions. The methods and systems enable a consumer to present a customer identifier, such as a merchant loyalty or membership card or other identifier as a payment device at a point of sale. In one implementation, a personal account number is generated by appending a proprietary routing code to a customer registration account number so that the personal account number is formatted for transmission as a payment device number over an electronic funds transfer network. In another implementation, the customer registration account number comprises the proprietary routing code. A preferred payment account identifier is accessed, based on the personal account number, from a database, and a transaction approval message is constructed comprising the preferred payment account identifier. The account from which payment is made may be a credit account, a demand deposit account, a stored value account, or another kind of account.