The gas certificate apps are being rewritten. See our device requirements below to see if your tablet or smartphone will be compatible,
The app will require your tablet or smartphone to be running Android version 6.0 (Marshmallow) or above, including the versions below:
6 - Marshmallow (2015)
7 - Nougat (2016)
8 - Oreo (2017)
You can check to see if your existing device is running this version (or higher) by going to settings > about/system > Android Version on your device.
The minimum requirements for iOS devices will be iOS 11.