What is the UK tax year and when does it start?
The UK tax year runs from 6 April to 5 April the following year. The 2025/26 tax year ran from 6 April 2025 to 5 April 2026, and HMRC writes it as 2025 to 2026. Your Self Assessment return for a tax year is filled in after that year ends on 5 April.
Figures checked against gov.uk on . General information, not tax advice.
At a glance
- Latest tax year
- 2025/26: 6 April 2025 to 5 April 2026
- Current tax year
- 2026/27: 6 April 2026 to 5 April 2027
- Return for 2025/26 due online
- 31 January 2027
How a tax year maps to a return
Each Self Assessment return reports one tax year. gov.uk says paper and online returns for the year that ended on 5 April 2026 could be sent from 6 April 2026, with the online deadline on 31 January 2027, so the gap between the end of the year and the deadline is nearly ten months.
The same naming is used across gov.uk. When a page says 2025 to 2026, it means this same 6 April to 5 April period, which is why you will see the slash and word forms used interchangeably.
Why the dates are not the calendar year
Income received on 3 April belongs to one tax year and income received on 8 April to the next, even though they are days apart. This is the reason the dividend, trading and property allowances, Marriage Allowance and the Personal Allowance are all quoted per tax year rather than per calendar year.
Self-employed profit is now allocated to tax years too, a change covered under basis period reform.