Self Assessment deadline: 31 January 2027, and what happens if you miss it
The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. If you are self-employed, or have other income that isn't taxed through payroll, its return and its tax are due on 31 January 2027 . This page has the dates, the penalties and a plan for the weeks in between.
The dates for the 2025/26 return
| Date | What it is |
|---|---|
| 5 October 2026 | Last day to tell HMRC you need to file for the first time. Registering later gets a different return deadline, set in a letter or email from HMRC. |
| 31 October 2026 | Paper return must reach HMRC. Most people file online instead. |
| 30 December 2026 | File online by this date if you want a bill under £3,000 collected through your tax code (PAYE employees only). |
| 31 January 2027 | Online return due, and the tax for 2025/26 due. The first payment on account towards 2026/27 is due the same day if you make them. |
| 31 July 2027 | Second payment on account. |
Both the return and the money are due by 11:59pm on 31 January. Filing on time doesn't stretch the payment date.
What a miss costs
From GOV.UK on 21 October 2026. Late returns: £100 straight away, then £10 a day after three months (up to £900), then 5% of the tax due or £300, whichever is greater, at six months and again at twelve. Late payment: 5% of the unpaid tax at 30 days, six months and twelve months, plus interest. Filing late and paying late are charged separately. If you have a genuine reason, HMRC lets you appeal a penalty.
What to do between now and January
- Now: get your income and expenses for 6 April 2025 to 5 April 2026 into one place. A spreadsheet that is already sorted by the return's boxes saves an evening.
- By mid-November: run your figures through the self-employed tax calculator so the amount isn't a surprise. It is set to 2025/26 and shows every payment date.
- By 30 December (if you also have a job): file online if you want a small bill taken through your tax code.
- In January: file, then pay. Check whether payments on account make January bigger than you expect.
Making Tax Digital for Income Tax is separate: it starts in April 2026 for people with qualifying income over £50,000 and doesn't change this 31 January. Check whether and when it covers you.
This is a planning guide, not tax advice. Check dates on GOV.UK.