The deadline for filing your self-assessment income Tax Return was delayed by a month. More exactly, if you submitted the return by 28 February, it was still late but HMRC would not charge you a penalty.
The date by which you need to pay your tax was also amended this year. The tax that ordinarily would have been due by 31 January only needed to be paid by the end of February.
Normally a surcharge of 5% would be added at the end of February to any tax not yet paid. However, this year the surcharge will be added on 1 April.
So, if you have not already paid your 2021 balancing payment, make sure you get it paid by 31 March to avoid the 5% surcharge.