Abstract: Customers can use their own mobile devices to pay for products in a “self-service” transaction, without the assistance of a store employee and without the need for the store to provide a self-service checkout kiosk. The customer's device communicates with a server maintained by the store to identify the product(s) being purchased and to provide a digital credential that the server can use to look up financial account information for the customer. The server can process a payment transaction to the financial account and notify the customer's device of the result. In some cases, an employee device can provide product identification for a purchase to the server and associate the customer device with the purchase, allowing the customer to complete the transaction directly with the store server.