To use Payment Code, a customer opens the PayPal app in-store and checks in. The app then generates a QR code and four digit code. If the shop has a barcode or QR code scanner, the phone is simply passed over it to make a purchase. Alternatively the code is entered into the POS PIN pad.

While the process fails to make paying at the checkout simpler than the old-fashioned card, PayPal argues that the real benefit to customers is the ability to automatically redeem things like special offers, gift cards and rewards programmes.

Meanwhile, merchants can tap into the 2D barcode scanners they already have in-store, rather than having to pay out for new hardware such as NFC-enabled terminals. PayPal also stresses that retailers which already have a mobile app for their customers can still use the feature, integrating it into their own offering.

Payment Code - launched today at the Money2020 conference, but not to be rolled out in the first quarter of next year - is an advance on PayPal's previous big checkout effort, deployed by retailers such as Home Depot, which required customers to use a physical 'Access' card or punch in a mobile phone number and PIN into the terminal.

The eBay unit is also experimenting with Bluetooh Low Energy technology, which can enable a transaction to take place without having to open up an app, without GPS being turned on, and even without a phone signal for establishments with thick concrete walls.

Meanwhile, in the UK it has been trialling mobile payments technology which lets customers verify themselves at the checkout using just a photo and their first name.