Abstract: Mobile device transactions are conducted at a POS terminal using gift card infrastructure. When a mobile device transaction is desired, a pre-designated gift card number is used at the POS terminal, which is recognized during gift card processing as assigned for use with mobile transactions and which results in an open invoice message. At the same time, a mobile device reads a QR code displayed at the POS terminal, in order to generate a transaction request. The open invoice message and transaction request are matched and processed at a mobile transaction processing system.