The UK tax year runs from 6 April to 5 April the following year, fixed by section 4 of the Income Tax Act 2007. The dates are a leftover of the 1752 calendar reform, and they set when your P60 and every year-to-date figure on a payslip reset.
Why 6 April and not 1 January?
The old tax year started on Lady Day, 25 March. In 1752 Britain dropped 11 days to adopt the Gregorian calendar; to avoid losing tax on those days the Treasury pushed the year-end to 5 April. A further calendar adjustment in 1800 moved the start to 6 April, where it has stayed. So the dates are not arbitrary, they preserve a full collection period from a 270-year-old accounting fix.
What resets at the start of a new tax year?
On 6 April several payroll figures begin again from zero:
- Your Personal Allowance, £12,570 for 2025/26, refreshes in full.
- Year-to-date gross pay, tax and National Insurance on your payslip reset to nil.
- Cumulative PAYE recalculates, which is why a tax code change often lands in April.
- Your employer must give you a P60 for the year just ended by 31 May.
- New rates and thresholds announced at Budget take effect for the year ahead.
Which tax-year deadlines should I diary?
| Date | What happens |
|---|---|
| 6 April | New tax year begins; allowances and year-to-date figures reset |
| 5 April | Previous tax year ends |
| 31 May | Deadline for your employer to issue your P60 |
| 31 October | Paper Self Assessment return deadline |
| 31 January | Online Self Assessment return and tax payment deadline |
Primary sources
- Income Tax Act 2007, section 4 — legislation.gov.uk — Defines the income tax year as 6 April to 5 April
- Self Assessment tax returns: deadlines — gov.uk — 31 October paper and 31 January online filing deadlines
- P45, P60 and P11D forms: P60 — gov.uk — Employer must issue a P60 by 31 May after the tax year ends
- Income Tax rates and Personal Allowances — gov.uk — 2025/26 allowance and bands that reset each 6 April
Editorial process: how we source and review UK tax content.