Answers · UK 2025/26
When is the Self Assessment deadline?
The online Self Assessment filing deadline is 31 January following the tax year (e.g. 31 January 2027 for the 2025/26 return). Paper returns are due by 31 October. Any tax owed is due on the same 31 January date.
Full answer
For the 2025/26 tax year (6 April 2025 to 5 April 2026), the Self Assessment deadlines are: 31 October 2026 for paper returns, 31 January 2027 for online filing, and 31 January 2027 for paying any balancing tax owed. If you make payments on account (because your previous year's tax was over £1,000), the second payment is due 31 July 2026 (for the 2024/25 tax year). Missing the deadline triggers an automatic £100 penalty even if no tax is owed. After 3 months, £10/day penalties accrue (up to £900). After 6 months, the greater of £300 or 5% of tax owed. After 12 months, another similar penalty. Interest is charged on late tax payments at HMRC's base rate + 2.5%. File on time even if you cannot pay — penalty for late filing is separate from penalty for late payment.
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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.