What's the deadline for my self-assessment tax return?

For the tax year ending 5 April 2025, the deadlines for self-assessment tax returns are:

31 October 2025 is the paper filing deadline. Please see our Knowledge Base article on: Can I file a paper return using TaxCalc? for further information on this.
30 December 2025 is the deadline to file your tax return online to HMRC, if you owe less than £3,000 and want it collected through next year's tax code.
31 January 2026 is the deadline to file your tax return online to HMRC.

If you miss the deadline you'll be subject to the late filing penalty rules.

There are two exceptions when the paper deadline is extended to 31 January 2026:

Certain people are excepted from the 31 October 2025 paper deadline – if this applies to you, HMRC will notify you.
HMRC's online systems can't accept certain items or combinations of information and this might mean that you can't file online. Where possible the TaxCalc program will advise you of this, but if you're in any doubt, TaxCalc Support will be able to help.

For more information regarding online filing please refer to What tax years can I file online?