UK Tax Year 2025-26: Key Dates, Deadlines & What They Mean
The UK tax year runs from 6 April to 5 April the following year — an unusual date that dates back to the switch from the Julian to the Gregorian calendar in 1752. When Britain adopted the Gregorian calendar and lost 11 days, the Treasury moved the tax year end forward to preserve a full 365-day year, landing on 5 April. The date has not moved since.
For 2025-26, the tax year opened on 6 April 2025 and closes on 5 April 2026. Here are every key date you need to know.
Key dates for 2025-26
| Date | What happens |
|---|---|
| 6 April 2025 | 2025-26 tax year begins. New rates, thresholds and allowances take effect. |
| 5 October 2025 | Deadline to register for Self Assessment if you need to file for 2024-25 for the first time. |
| 31 October 2025 | Deadline to submit a paper Self Assessment return for 2024-25. |
| 31 January 2026 | Deadline to submit your online Self Assessment return for 2024-25, pay any tax owed, and make your first payment on account for 2025-26. |
| 31 May 2026 | Employers must issue P60 forms to all employees still in employment at 5 April 2026. |
| 5 April 2026 | 2025-26 tax year ends. |
| 6 April 2026 | 2026-27 tax year begins. |
Payment on account dates
If you pay tax via Self Assessment and your bill exceeds £1,000, HMRC requires you to make advance payments (payments on account) towards the following year. For the 2024-25 bill:
- 31 January 2025: First payment on account (50% of 2023-24 bill)
- 31 July 2025: Second payment on account (50% of 2023-24 bill)
- 31 January 2026: Balancing payment for 2024-25 + first payment on account for 2025-26
Why the 5 April end date matters for allowances
Most tax allowances reset at midnight on 5 April. Your ISA allowance (£20,000), pension annual allowance, and capital gains annual exempt amount all expire at this point and cannot be carried forward. If you have unused allowance, use it before the year ends.
Frequently asked questions
When does the 2025-26 tax year end?
5 April 2026. The new tax year (2026-27) begins on 6 April 2026.
When is the Self Assessment deadline for 2025-26?
You will file the 2025-26 return after the tax year ends. The online deadline is 31 January 2027, the paper deadline is 31 October 2026, and you must register by 5 October 2026 if it is your first time.
When must my employer give me my P60?
By 31 May 2026 for the 2025-26 tax year. If you left your job during the year you receive a P45, not a P60.