A notable difference between a mobile payment system and other electronic payment systems is the identification of the customer (and the merchant). In a mobile payment system, this identification is the GSM phone number. In other systems it is either the bank account number, or an interim account. The implication is that one can send funds to and retrieve funds from a phone number, rather than the bank account. This is similar to payment systems that rely on the customer’s e-mail address as the prime identifier (e.g. PayPal).