UK payments app Zapp has closed deals with five of the country’s major financial institutions ahead of its launch later this year, although three of the biggest banks have so far escaped its grasp.

HSBC, First Direct, Nationwide, Santander and Metro Bank have all agreed to integrate Zapp into their existing mobile banking apps.

However Barclays, Lloyds Banking Group and Royal Bank of Scotland have so far not signed up to Zapp.

The no-shows are interesting since they number among the 18 banks and building societies who own VocaLink, the UK payment system behind Zapp.

To date, VocaLink has invested £33 million in developing the app, according to Financial Times. The app is due to launch between September and October this year.

However, some banks, including Barclays, have developed their own mobile payment services independent of VocaLink.

Initially, Zapp will only work for online purchases. In-store mobile payments will not be available until late 2015.

The advantage of direct integration with a banking app is that subscribers can use Zapp to make real-time payments from their current accounts, with less long card numbers, passwords and user names to remember.