Answers · UK 2025/26
When do I file self-assessment 2026?
For the 2025/26 tax year (6 April 2025 – 5 April 2026), the online self-assessment deadline is 31 January 2027. Paper returns are due 31 October 2026. The same 31 January 2027 date is the deadline for paying any tax owed plus the first 2026/27 payment on account.
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Key 2025/26 self-assessment dates: 6 April 2026 — earliest you can file; 5 October 2026 — register if newly self-employed or otherwise newly liable; 31 October 2026 — paper return deadline; 30 December 2026 — file online if you want HMRC to collect tax owed under £3,000 via PAYE; 31 January 2027 — online filing deadline and balancing payment + first payment on account for 2026/27; 31 July 2027 — second payment on account. Penalties: £100 immediate fixed penalty for missing 31 January; daily £10 penalties after three months (up to £900); 5% surcharges on unpaid tax at 30 days, six months and twelve months; plus interest (Bank of England base rate + 2.5% — currently around 7.25%). You can appeal if you have a reasonable excuse (illness, bereavement, HMRC system failure). MTD for ITSA will apply from April 2026 to sole traders and landlords with income over £50,000 (and from April 2027 for £30,000+) — quarterly digital updates will be required in addition to year-end submission.
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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.