HMRC has been issuing the notices to complete 2020 tax returns – if these arrive in the post they are called a SA316 form.
If you have a personal tax account, then you will receive a message (as above) containing the same information.
These notices to complete a tax return are a standard format, setting out the requirement to complete a return and the deadlines that apply.
For those completing a return on paper, I have previously advised that this year HMRC are no longer automatically issuing paper tax returns.
It is important to complete the tax return as soon as possible, so that your tax position can be agreed and the upcoming tax payments through to January (or July) 2021 can be planned for.
The January 2021 liability may be much larger than normal if the 31st July 2020 payment on account has been deferred.
It may also be possible to collect any tax you owe through your tax code in a later year – but the return has to be with them before the end of December.