What is a UK Tax Year?
The UK tax year (also called the fiscal year or tax period) runs from 6 April to 5 April the following year. It's the 12-month period over which your income is calculated for tax purposes.
The tax year running from 6 April 2026 to 5 April 2027 is referred to as the 2026/27 tax year.
Every tax year, your Personal Allowance, tax bands and other entitlements reset. This is when PAYE tax codes are updated, and it's the reference period for annual reporting.
Why Does the Tax Year Start on 6 April?
The odd start date is historical. In 1752, Britain switched from the Julian to the Gregorian calendar, losing 11 days. The old new year (25 March) became 5 April in the new calendar. In 1800, a leap year in the Julian calendar but not the Gregorian added one more day, shifting it to 6 April — and it's stayed there ever since.
Key Dates in the Tax Year
Important milestones
- 6 April — New tax year begins. Allowances reset, new tax rates apply.
- 31 January — Self Assessment deadline (online filing + payment), plus first payment on account due.
- 31 July — Second payment on account due for self-employed.
- 5 October — Deadline to register for Self Assessment if you need to file for the previous tax year.
- 5 April — End of the tax year. Last day for ISA deposits that count toward your annual allowance.
- 31 October — Paper Self Assessment return deadline (if you still file on paper).
Your Allowances Reset Every April
On 6 April each year, your tax allowances start afresh:
- Personal Allowance — £12,570 for 2026/27 (unchanged since 2021/22)
- Personal Savings Allowance — up to £1,000 for basic rate taxpayers
- ISA Allowance — £20,000 per year (use it or lose it!)
- Capital Gains Tax annual exempt amount — £3,000 for 2026/27
- Dividend Allowance — £500 for 2026/27
💡 Your allowances don't roll over. If you don't use your ISA allowance by 5 April, it's gone forever. The same applies to your annual CGT exempt amount.
Tax Years vs Academic Years
Don't confuse the tax year with the academic year (September to August) or financial year for companies (often January to December or April to March). For individuals, the HMRC tax year always runs April to April — this is what matters for PAYE and Self Assessment.
What Happens at Tax Year End?
As 5 April approaches, several things happen:
- Your employer issues a P60 (usually by 31 May) summarising your pay and tax for the year.
- Your P11D (benefits in kind) is due to HMRC by 6 July.
- HMRC sends out P800 forms if you've overpaid or underpaid tax.
- Your new tax code for the coming year is issued — often in January or February.
🔴 If you're self-employed, the tax year ending 5 April 2026 means your Self Assessment return must be filed online by 31 January 2027 — don't leave it to the last minute.
Tax Year for Self Assessment
If you're self-employed or need to file a tax return, the tax year defines your accounting period for tax. Even if your business year ends on a different date, you need to report income and expenses for each tax year (6 April to 5 April).
This can create a basis period where your first year of trading may be longer than 12 months. From 2024/25 onwards, the "tax year basis" applies, meaning you're taxed on what you earned in the tax year, not your accounting year.
How Tax Codes Change at Year End
At the start of each tax year, HMRC issues new tax codes. Your code number reflects your Personal Allowance — currently 1257L. If your circumstances haven't changed, you'll likely see the same code year after year.
However, if you owe tax from a previous year, HMRC may adjust your code to collect it — this is common after underpayments of £3,000 or less.
Learn more about what each letter means in our tax codes guide.
Why You Should Plan Around 5 April
The end of the tax year is one of the most important dates for smart tax planning:
Smart moves before 5 April:
- Max out your ISA allowance — invest before midnight on 5 April
- Use your pension annual allowance (£60,000 for 2026/27) — contributions get tax relief
- Claim any expenses or charitable donations before the year closes
- Consider gifting assets to use your £3,000 CGT annual exempt amount
- Make sure you've used your £500 dividend allowance if relevant
💡 Carry forward rules: For pensions, you can use unused annual allowance from the previous three tax years. For ISAs, there's no carry forward — so prioritise using what you have.
Tax Years at a Glance
Current and recent tax years
- 2026/27 — 6 April 2026 to 5 April 2027 (current)
- 2025/26 — 6 April 2025 to 5 April 2026 (just ended)
- 2024/25 — 6 April 2024 to 5 April 2025
- 2023/24 — 6 April 2023 to 5 April 2024