Answers · UK 2025/26
What happens if you don't file your Self Assessment tax return?
You'll face an automatic £100 penalty from 31 January, rising to £10 per day after 3 months (up to £900 additional), plus 5% surcharges on unpaid tax at 6 and 12 months, plus 7.5% interest on late payments.
Full answer
HMRC operates a strict penalty regime for late Self Assessment filing and late payment. Here is the full penalty ladder for the 2025/26 tax return (due 31 January 2027): **Late filing penalties:** | When filed | Penalty | |---|---| | 1 day late (from 1 Feb 2027) | £100 fixed penalty | | 3 months late (from 1 May 2027) | £10/day for up to 90 days (max £900 additional) | | 6 months late (from 31 July 2027) | Greater of £300 or 5% of tax due | | 12 months late (from 31 Jan 2028) | Greater of £300 or 5% of tax due (further 5%) | | Deliberate withholding | Up to 100% of tax owed | **Late payment interest:** HMRC charges interest at the Bank of England base rate plus 4% on unpaid tax from 31 January. **Late payment surcharges:** - 30 days late: 5% of unpaid tax - 6 months late: further 5% - 12 months late: further 5% **Reasonable excuse:** HMRC can waive penalties if you have a genuine "reasonable excuse" — such as serious illness, bereavement, or IT failure. Excuses must be reported promptly. Ignorance of the law and lack of funds are generally not accepted. **HMRC Time to Pay:** If you cannot pay your tax bill, contact HMRC before the deadline to arrange a Time to Pay instalment plan. Penalties still accrue for late filing, but a payment arrangement stops further debt escalation. **How to appeal:** Appeals must be submitted within 30 days of the penalty notice on GOV.UK (or by letter). HMRC will review; if refused, you can request a Statutory Review and ultimately appeal to the Tax Tribunal.
Try the calculator
Related guides
This answer is informational only and does not constitute financial, tax or legal advice. Figures are for the 2025/26 UK tax year. See our methodology and sources.