HMRC says:
New improvements to the HMRC app
The HMRC app has been updated and improved to include quick and easy ways for users to make a Self Assessment payment and get their employment details (such as income and employment history) going back five years.
They can have instant access to their employment and income history, National Insurance number and tax codes all at a touch and can also print and download this information to share if needed, meaning they don’t have to call us or wait for it to come in the post.
To showcase the simplicity and usefulness of the app we have created a series of ‘how to use the app’ videos on YouTube, where you can find out how to confirm your employment details and make a Self Assessment payment on GOV.UK.