The dates that actually matter
If you need to file a Self Assessment return for the 2025–26 tax year (6 April 2025 to 5 April 2026), HMRC’s online deadline is 11:59pm on 31 January 2027. That is also when the tax itself is due, unless you are paying through your tax code.
Paper returns had to reach HMRC by 31 October 2026. If you want any balancing payment collected through PAYE, you needed to file by 30 December 2026.
Registering after 5 October 2026 usually means HMRC gives you a later filing date — three months from their letter — but the 31 January 2027 payment date still stands.
Who still has to file a “normal” return
Sole traders, many landlords, company directors with untaxed income, and people with capital gains still file Self Assessment for 2025–26 in the usual way. Making Tax Digital for Income Tax started in April 2026 for some people, but it does not replace this year’s return.
What happens if you miss it
A late return typically attracts an immediate £100 penalty, then daily penalties after three months, and larger charges at six and twelve months. Interest also runs on unpaid tax. File as soon as you can — waiting rarely reduces the bill.
How to get it done without a January scramble
- Gather bank statements, invoices, mileage and property records now, not in January.
- Include payments on account if last year’s bill was over £1,000 and less than 80% was collected at source.
- The second payment on account is due 31 July 2027.
If you would rather not do this yourself, our Self Assessment service is built around a named accountant and a calendar you can see.
This article is general information for UK readers, not personal tax advice. Rules change. Check GOV.UK or speak to us before you file.