The UK tax year runs from 6 April to 5 April. Here's every important date for the 2026/27 tax year.
Key Dates
| Date | Deadline |
|---|---|
| 6 April 2026 | Start of 2026/27 tax year |
| 31 May 2026 | Employer must give you P60 for 2026/27 |
| 6 July 2026 | Employer must submit P11D (benefits) to HMRC |
| 5 October 2026 | Register for Self Assessment (if newly self-employed) |
| 31 October 2026 | Paper Self Assessment tax return deadline |
| 31 December 2026 | Deadline if you want tax collected via PAYE (owed < £3,000) |
| 31 January 2027 | Online Self Assessment return + payment deadline |
| 31 January 2027 | First payment on account for 2026/27 |
| 5 April 2026 | End of 2026/27 tax year — last day to use allowances |
| 5 April 2026 | Last day to use ISA allowance for 2026/27 |
| 31 July 2026 | Second payment on account for 2026/27 |
Why 6 April?
The UK tax year starts on 6 April due to a quirk of history. When Britain switched from the Julian to Gregorian calendar in 1752, 11 days were lost. To avoid losing tax revenue, the Treasury moved the start of the tax year from 25 March (Lady Day) forward by 11 days to 5 April — and then by one more day to 6 April during a later adjustment.
Use It or Lose It: 5 April Deadline
Several allowances expire on 5 April and cannot be carried forward: your £20,000 ISA allowance, your £3,000 CGT annual exemption, your £3,000 annual gift exemption (can carry forward one year only), and your £4,000 Lifetime ISA allowance.
Penalties for Missing Deadlines
Miss the 31 January Self Assessment deadline and you'll face an immediate £100 fine, even if you owe no tax. After 3 months, daily penalties of £10 apply (up to £900). After 6 months, a further £300 or 5% of tax owed (whichever is greater). After 12 months, another £300 or 5%.
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