The UK Tax Year Explained: Dates and Deadlines

The UK tax year runs from 6 April to 5 April the following year, which often confuses people used to a calendar year. This guide explains why, sets out the key dates, and shows how the tax year affects your rebate.

When is the UK tax year?

The UK tax year starts on 6 April and ends on 5 April the next year. So the 2026/27 tax year runs from 6 April 2026 to 5 April 2027. Each tax year is referred to by the two calendar years it spans.

Why does it start on 6 April?

The date is a historical quirk. Centuries ago the new year and the tax year began on 25 March. When Britain changed from the Julian to the Gregorian calendar in the 1750s, days were skipped to realign the calendar, and to avoid losing tax revenue the year end was shifted, eventually settling on 5 April. The start of the next day, 6 April, has marked the start of the tax year ever since.

Key dates in the tax year

A few dates matter for most people.

• 6 April: the new tax year begins, and new tax codes and allowances take effect.
• 31 May: employers must give employees their P60 for the previous tax year by this date.
• 6 July: employers must provide P11D details of benefits by this date.
• 5 October: deadline to register for Self Assessment if you need to file for the first time.
• 31 October: deadline for paper Self Assessment returns.
• 31 January: deadline for online Self Assessment returns and to pay any tax owed.

How the tax year affects your rebate

Your right to claim a tax rebate is measured in tax years. You can usually claim for the current tax year plus the previous four, and the oldest year drops off each 5 April. That is why claiming sooner can protect an extra year. See our guide on how far back you can claim.

Your tax code also resets with the tax year, so the start of a new year is a good time to check it is correct.

Frequently asked questions

What dates does the 2026/27 tax year cover?

It runs from 6 April 2026 to 5 April 2027.

Why does the tax year not match the calendar year?

It is a historical legacy of the switch from the Julian to the Gregorian calendar and old quarter days, which left the year end at 5 April.

When is the Self Assessment deadline?

Online returns and payment are due by 31 January following the end of the tax year. Paper returns are due by 31 October.

Why does the tax year matter for my rebate?

Claims are counted in tax years, and you can usually go back four years plus the current one. A year drops off each 5 April.

Make the tax year work for you

The start of a tax year is the perfect time to check your tax code and claim anything you are owed.

Check what you are owed with TaxPro, on a no win, no fee basis.