Normal due date
Individuals are required to pay any outstanding income tax, Class 2 and Class 4 national insurance, and capital gains tax due for the tax year by 31 January following the end of the tax year (ie 31 January 2023 for the 2021/22 tax year). From 6 April 2020, UK resident individuals who dispose of residential UK property are required to make a payment of capital gains tax within 60 days of completion (30 days prior to 27 October 2021). This applies to non-resident individuals in relation to disposals of UK property (whether or not this is residential property) from 6 April 2019. See the Disposals of UK land ― capital gains tax compliance regime guidance note.
For those who were required to notify HMRC of their chargeability by 5 October after the end of the tax year, but did not receive a notice to file a tax return until after 31 October, this payment deadline is extended. The taxpayer has three months from the date of the notice to file the tax return and pay the tax due. There was an interesting Tribunal case on this point, which is discussed in ‘Do not pay £200’ by Mike Truman in Taxation, 13 May 2010, 22.
Missing the payment deadline means interest and penalties can become due. See the Interest and penalties on late paid tax under self assessment guidance note.
It is not possible to offset one year’s tax refund against another year’s tax