The following announcement was released by HMRC on 25th January:
Today HMRC has announced that Self Assessment customers will not receive a penalty for filing their 2019-20 tax return late, as long as they file online by 28 February. We are still encouraging customers who have not yet filed to do so by 31 January, if possible.
Customers still need to pay their Self Assessment tax bill by 31 January. Interest will be charged from 1 February on any outstanding liabilities. Customers can pay online, or through their bank, or by post before they file.
If any customer cannot afford to pay by 31 January, they may be able to set up an affordable plan and pay in monthly instalments. But they will need to file their 2019-20 tax return before setting up a time to pay arrangement.
See more here