UK Tax Year Dates and Deadlines for 2026/27

Why the tax year starts on 6 April

The old tax year began on Lady Day, 25 March. When Britain switched from the Julian to the Gregorian calendar in 1752, 11 days were dropped, and the Treasury moved the year end to keep a full 365 days of collection. A further adjustment in 1800 left us with 6 April.

Key dates for 2026/27

Penalties for missing Self Assessment deadlines

• £100 fixed penalty if your return is up to 3 months late, even if you owe nothing.
• After 3 months, £10 a day for up to 90 days.
• After 6 months and again after 12 months, the higher of 5% of tax due or £300.
• Late payment: interest from the due date, plus late payment penalties at 30 days, 6 months and 12 months.

The payroll year

For PAYE, the tax year is split into tax months running from the 6th of one month to the 5th of the next (month 1 is 6 April to 5 May) and tax weeks starting from 6 April. Your payslip tax figures are cumulative from 6 April. Employers report each payment to HMRC under Real Time Information on or before payday and send a final submission for the year by 19 April.

Because 52 weeks is 364 days, weekly-paid staff can occasionally receive 53 paydays in a tax year, known as week 53. In that week PAYE uses a non-cumulative basis.

Making Tax Digital for Income Tax

From 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates using compatible software. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Quarterly updates are due on 7 August, 7 November, 7 February and 7 May. You still file a final return by 31 January.

Payments on account explained

If your last Self Assessment bill was £1,000 or more and less than 80% of your tax was collected at source (for example through PAYE), HMRC asks for advance payments towards the next year. Each payment on account is half of the previous year's bill.

Example: your 2025/26 bill is £4,000. By 31 January 2027 you pay the £4,000 balancing payment plus a first £2,000 payment on account for 2026/27. A second £2,000 is due by 31 July 2027. If your 2026/27 bill turns out to be £5,000, you pay the extra £1,000 by 31 January 2028. If your income has dropped, you can apply to reduce payments on account.

Before 5 April 2027: a year-end checklist

Several allowances are use-it-or-lose-it and reset on 6 April, so March is the time to use them.

Documents you get through the year

Your employer and HMRC send a predictable set of documents. Keep them for at least 22 months after the end of the tax year if you file a return, or longer if you are self-employed.

• P45: when you leave a job. Parts 2 and 3 go to your new employer so the right tax code applies.
• P60: by 31 May, showing total pay and tax for the year from each employer you work for on 5 April.
• P11D: by 6 July, listing benefits in kind not taxed through payroll. From April 2027 company cars, fuel, vans and medical benefits must be payrolled instead.
• Tax code notice (P2): whenever HMRC changes your code, often in January to March for the coming year.
• P800 or Simple Assessment: between June and March after the year ends, if you paid the wrong tax under PAYE.

Different year ends you may meet

Not every UK tax runs from 6 April. Companies pay Corporation Tax by financial year, 1 April to 31 March, and on their own accounting periods. VAT returns follow quarters set by HMRC when you register. Business rates and council tax are billed on a 1 April to 31 March year.

For sole traders, basis period reform means profits are taxed on the tax year from 2024/25 onwards. Accounts drawn up to 31 March are treated as matching the tax year, which is why many small businesses use a 31 March or 5 April year end.

Timing that changes what you pay

• A bonus paid on 5 April counts in the old year. On 6 April it counts in the new year, with fresh bands and allowances.
• Pension contributions only count for the tax year in which they are paid, so a payment on 5 April can still cut that year's adjusted net income.
• Selling shares just before or after 5 April decides which year's £3,000 CGT allowance and which year's tax rates apply.
• Gift Aid donations can be carried back to the previous year if you claim on a return filed by its normal deadline.