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Last updated: 9 November 2026

Taxes

Tax Year Dates: UK Tax Year Start, End and Key Deadlines

The UK tax year runs from 6 April to 5 April, and almost every tax date hangs off those two days. This guide sets out the 2025/26 and 2026/27 tax years and explains why the year starts on 6 April.

MKD Editorial Team6 min readFigures checked 9 Nov 2026
A blank wall calendar, reading glasses, blank papers and a cup of tea on a wooden desk in warm morning light.
A blank calendar is the simplest way to see the tax year at a glance.

Key takeaways

  • The 2026/27 tax year runs from 6 April 2026 to 5 April 2027.
  • The 2025/26 online return and any tax owed are due by 31 January 2027.
  • Paper returns for 2025/26 were due 31 October 2026; first-timers registered by 5 October 2026.
  • Unused ISA allowance disappears on 5 April: use it or lose it.
  • A late online return brings an automatic £100 penalty, even if you owe no tax.

What the UK tax year is

The UK tax year, sometimes called the fiscal year, runs from 6 April to 5 April the next year. It is the 12 months HMRC uses to work out income tax. Each year is named after the two calendar years it spans, so 6 April 2026 to 5 April 2027 is 2026/27.

The 2025/26 tax year ran from 6 April 2025 to 5 April 2026, and its deadlines fall in late 2026 and January 2027. The return filed in January 2027 covers 2025/26 income, not the year you are living in when you file it.

Why the tax year starts on 6 April

The odd date is a leftover from a calendar change in 1752. Before then, England used the Julian calendar and the legal year began on 25 March, known as Lady Day. When Britain switched to the Gregorian calendar that September, eleven days were dropped.

The Treasury did not want to lose eleven days of tax revenue, so the tax year moved forward by eleven days, from 25 March to 5 April. A further adjustment in 1800 moved it one more day, to 6 April. Section 4 of the Income Tax Act 2007 now defines the tax year as 6 April to the following 5 April.

Tax year vs calendar year

Your payslip runs on the calendar year, 1 January to 31 December. Your tax does not. Income earned on 5 April belongs to the tax year that is ending, while income earned on 6 April belongs to the new one. The same bonus paid on 5 April and on 6 April falls in different tax years.

The government's own financial year is different again: it runs from 1 April to 31 March. Your tax code and thresholds reset on 6 April each year.

Key dates for the 2025/26 tax year

The 2025/26 year ended on 5 April 2026, but its deadlines stretch into 2027:

  • 5 October 2026: tell HMRC you need to file for the first time.
  • 31 October 2026: paper returns must reach HMRC by 11:59pm.
  • 30 December 2026: file online by now to pay a bill under £3,000 through your tax code.
  • 31 January 2027: online return and any tax owed due by 11:59pm, plus the first payment on account.
  • 31 July 2027: second payment on account, if you make them.

You can file any time after 5 April; no need to wait until January. Register late and HMRC sets your own deadline three months from its letter; tax is still due by 31 January. Our Self Assessment tax return guide explains who needs to file and how it works.

31 January 2027 is a Sunday and 31 July 2027 a Saturday, so Bacs payments must reach HMRC by the Friday before, 29 January and 30 July.

A man in a navy shirt writing in a blank notepad at a wooden kitchen table, with a laptop and a mug of tea beside him.
Most tax dates are set by the year that just ended, not the one you are living in.

Key dates for the 2026/27 tax year

The 2026/27 tax year ends on Monday 5 April 2027, and its tax year dates follow the same pattern. Register by 5 October 2027 if you are new to Self Assessment, send paper returns by 31 October 2027, file by 30 December 2027 to pay through your tax code, and file online and pay by Monday 31 January 2028. A second payment on account falls due on Monday 31 July 2028, if you make them.

Your employer must give you a P60 by 31 May 2027 and P11D benefits information by 6 July 2027. Each payment on account is half of the previous year's tax bill. If all your income is taxed through PAYE, none of this applies. If your code looks wrong, our 1257L tax code guide explains what the numbers mean.

What happens on 5 April: use it or lose it

Midnight on 5 April is the deadline for the year's allowances. Your ISA allowance for 2026/27 is £20,000: anything unused by 5 April 2027 is gone, and next year's allowance is still just £20,000. The capital gains exempt amount, £3,000 for individuals in 2026/27, works the same way.

Pensions are more forgiving: the £60,000 annual allowance for 2026/27 can usually be carried forward up to three tax years, if you belonged to a registered pension scheme in each of them. Our guide to the state pension age sets out when the State Pension itself begins.

Worked example, labelled illustrative: if you paid £12,000 into ISAs by March 2027, your remaining allowance is £20,000 minus £12,000, or £8,000. Unused on 5 April, that £8,000 is lost, and your 2027/28 allowance is £20,000, not £28,000.

What happens if you miss a deadline

A late online return brings an automatic £100 penalty, even if you owe no tax. After three months, HMRC adds £10 a day, up to £900. At six months there is a further £300 or 5% of the tax due, whichever is higher, and again at twelve months. Paying late adds 5% of the tax still unpaid at 30 days, six months and twelve months, plus interest at 4% above the Bank of England base rate.

If you cannot pay in full, file anyway: filing stops the late-filing penalties growing, and HMRC may agree a payment plan.

Sources & further reading

This article is general information only, not financial advice.

Related guides

Frequently asked questions

When does the UK tax year start and end?

The UK tax year starts on 6 April and ends on 5 April the following year. The 2026/27 tax year runs from 6 April 2026 to 5 April 2027, and the 2025/26 tax year ran from 6 April 2025 to 5 April 2026. Every tax year is named after the two calendar years it spans.

When is the Self Assessment deadline for 2025/26?

The online Self Assessment return for 2025/26 is due by 11:59pm on Sunday 31 January 2027, and any tax you owe for that year must be paid by the same date. Paper returns had to reach HMRC by 31 October 2026, and first-time filers had to register by 5 October 2026.

What is the last day to use my ISA allowance?

The last day is 5 April, the final day of the tax year. Your ISA allowance for 2026/27 is 20,000 pounds, and anything you have not used by 5 April 2027 is lost: it cannot be carried into the next tax year, and the next year allowance is still 20,000 pounds.

Why does the UK tax year start on 6 April?

It is a leftover from a calendar change in 1752. Before then the legal year began on 25 March, known as Lady Day. When Britain switched to the Gregorian calendar, eleven days were dropped, and the Treasury moved the tax year forward by the same eleven days to 5 April so it would not lose revenue. A further adjustment in 1800 moved it to 6 April, where it has stayed.

What happens if I miss the 31 January deadline?

HMRC charges an automatic 100 pound penalty, even if you owe no tax. After three months it adds 10 pounds a day, up to 900 pounds, and further penalties of 300 pounds or 5 percent of the tax due apply at six and twelve months. Late payment brings its own penalties plus interest, so file the return even if you cannot pay in full.

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