Abstract: A method for execution on a computing device includes the steps of receiving information from a user to be included in a user profile, and establishing a user account associated with the user profile. The account has an identifier and an account balance; the balance is in accordance with funds expended by the user or received by transfer from another user. A user device is caused to display an image representing the account identifier; an external system (e.g. at a retailer) is permitted access to the account by recording the image. A user-initiated transaction (e.g. a retail purchase) is processed in accordance with information transmitted by the external system (e.g. over a network); this processing includes updating the account balance in accordance with the transaction. The displayed image may be a bar code scannable by the external system.