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Self Assessment Deadline & Penalty
Find your UK Self Assessment deadlines and estimate HMRC's late-filing penalties. The online deadline is 31 January, and missing it triggers an immediate £100 penalty — then daily charges after 3 months and percentage penalties at 6 and 12 months. Pick your tax year and how late you'll be to see the figures.
Your Self Assessment deadlines & penalty estimate
Choose the tax year and how late you expect to be. Penalty amounts use HMRC’s standard structure and are indicative.
Key dates for 2025/26
- 31 October 2026 — paper return deadline.
- 31 January 2026 — online return deadline and balancing payment due.
- 31 July 2026 — second payment on account (if applicable).
Estimated late-filing penalties
No filing penalty — you’re on time.
Indicative only, based on HMRC’s standard penalty structure. A reasonable excuse can reduce or cancel penalties, and partnership returns differ. We can check your exact position.
Behind on a return, or facing penalties?
We file Self Assessment returns for cross-border clients and can often reduce penalties with a reasonable-excuse claim. The first consultation is free.
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Frequently asked questions
For online returns, the deadline is 31 January following the end of the tax year (which runs to 5 April). Paper returns are due earlier, by 31 October. Any tax owed is also due by 31 January, with a possible second payment on account on 31 July.
You get an automatic £100 penalty the moment you miss the deadline, even if you owe no tax or have nothing to pay. After 3 months, daily penalties of £10 apply for up to 90 days (a maximum of £900). After 6 months and again after 12 months, a further penalty of the greater of 5% of the tax due or £300 is charged.
Yes — they are separate. Late-filing penalties apply for submitting the return late; late-payment penalties (broadly 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest) apply for paying the tax late. You can be charged both.
Sometimes. If you have a reasonable excuse for filing or paying late, HMRC may cancel or reduce the penalty on appeal. What counts as a reasonable excuse is fact-specific, so it is worth getting advice before assuming you must pay.
Behind on Self Assessment?
We file cross-border Self Assessment returns and can often reduce penalties with a reasonable-excuse claim.