Setting up a personal gateway accountLast updated: 16 Jul 2020
You must have or set up a Personal Tax Account to receive your tax return before you hit our Submit button in the app.
Registering for the Personal Tax Account only takes a couple of minutes and means submitting your tax return is efficient, effective and easy.”
Customers submitting their tax return online for the first time will need to register for an activation code, (which activates your account) HMRC will be post it to your home address, it can take up to seven days to arrive.
It's very straightforward.
Follow this link: https://www.gov.uk/personal-tax-account