The UK tax year runs from 6 April to 5 April the following year. The current tax year, 2026 to 2027, started on 6 April 2026 and ends on 5 April 2027. The last one ran from 6 April 2025 to 5 April 2026, and its Self Assessment online return is due by 11:59pm on 31 January 2027.
That's the year for individuals: employees, the self-employed and anyone filing Self Assessment. Limited companies work to a different calendar, which is where most of the confusion comes from.
UK tax year dates at a glance
| Tax year | Starts | Ends |
|---|---|---|
| 2025 to 2026 | 6 April 2025 | 5 April 2026 |
| 2026 to 2027 (current) | 6 April 2026 | 5 April 2027 |
| 2027 to 2028 | 6 April 2027 | 5 April 2028 |
When HMRC writes "the 2025 to 2026 tax year", it means the 12 months ending on 5 April 2026. Your Self Assessment return for that year is the one you're filing now.
Self Assessment deadlines for 2025 to 2026
| What | Deadline |
|---|---|
| Tell HMRC you need to file (first time, or not needed last year) | 5 October 2026 |
| Paper return must be received by HMRC | 11:59pm on 31 October 2026 |
| Online return, if you want HMRC to collect through your tax code | 11:59pm on 30 December 2026 |
| Online return | 11:59pm on 31 January 2027 |
| Balance of tax due | 11:59pm on 31 January 2027 |
The catch with paper returns is the word received: HMRC must have it by 31 October, not just have it posted. And if you register after 5 October 2026, HMRC sends you a letter or email with your own deadline, 3 months from the date on it, but the tax itself is still due by 31 January 2027.
You can file any time from 6 April 2026, so there's nothing stopping you getting it done in spring.
Sole traders: the tax year basis
This changed recently, and it trips up sole traders with an unusual year end. Since 6 April 2023, the self-employed and trading partnerships report income for the tax year itself, 6 April to 5 April, even if their business accounts end on a different date. HMRC calls it the tax year basis, also known as basis period reform.
- If your accounting year ends on or between 31 March and 5 April, you put your accounts figures in your return as normal.
- If it ends on any other date, say 31 December, you add together the part from 6 April to your year end and the part from your new year start to 5 April, usually split by the number of days.
- Employees and company directors aren't affected.
HMRC's own tip: you can prepare accounts to any date, but making your year end 31 March or 5 April means you only need one set of accounts for each return. If your year end is 31 March to 4 April, you can treat it as ending on 5 April.
The switch happened in the 2023 to 2024 tax year, which HMRC calls the transition year. Anyone affected reported more than 12 months of income that year, and the extra part can be spread over the following years, up to the 2027 to 2028 tax year. So if your return still shows a transition figure, that's why, and it'll keep appearing until the spreading ends.
Limited companies: a different year
Companies don't use the 6 April tax year for Corporation Tax. A company's accounting period is the time covered by its Company Tax Return. It can't be longer than 12 months and is normally the same as the financial year covered by its annual accounts, which the company chooses.
Corporation Tax rates themselves are set for a financial year starting on 1 April. If your accounting period straddles 1 April and the rates change, you work out how many days each rate applied. Check your accounting period dates by signing in to your business tax account with HMRC.
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| Who | Year that matters |
|---|---|
| Employees | 6 April to 5 April (PAYE and tax code) |
| Sole traders and partnerships | 6 April to 5 April (tax year basis) |
| Limited companies | Their own accounting period, up to 12 months |
| Corporation Tax rates | Financial year from 1 April |
Checking your current year
If you're employed, GOV.UK's Check your Income Tax for the current year service, or the HMRC app, shows your tax code and estimated income for 6 April 2026 to 5 April 2027. It doesn't work if Self Assessment is the only way your Income Tax is collected. If you're self-employed and wondering when quarterly digital reporting starts for you, our guide to the Making Tax Digital threshold explains who comes in when.
My advice
Put 5 October, 31 October, 30 December and 31 January in your calendar every year, and file in spring while the year is fresh. If you're a sole trader with an odd year end, think about moving it to 31 March: one set of accounts per return is far less work. And if you're starting a business in the UK, pick your year end with this in mind from day one.
Frequently asked questions
When does the UK tax year start and end?
The UK tax year starts on 6 April and ends on 5 April the following year. The 2026 to 2027 tax year runs from 6 April 2026 to 5 April 2027.
What is the Self Assessment deadline for the 2025 to 2026 tax year?
Online returns must be submitted by 11:59pm on 31 January 2027, and paper returns must reach HMRC by 11:59pm on 31 October 2026.
Do limited companies use the 6 April tax year?
No. A company's Corporation Tax works on its accounting period, which can't be longer than 12 months and normally matches its own financial year. Corporation Tax rates are set for financial years starting on 1 April.
What is the tax year basis for sole traders?
Since 6 April 2023, sole traders and trading partnerships report income for the tax year, 6 April to 5 April, even if their accounts end on a different date. Accounts ending between 31 March and 5 April can be used as they are.
When do I need to register for Self Assessment?
You must tell HMRC by 5 October if you need to complete a tax return for the previous tax year and you haven't sent one before, or you didn't need to send one last year.
