The UK tax year runs from 6 April to 5 April the following year. Unlike the calendar year or most other countries, the UK tax year dates back to a calendar reform in 1752 and has been preserved ever since. Here's what that means for your allowances, deadlines, and tax planning in 2026/27 and beyond.
The UK tax year: 6 April to 5 April
The UK tax year (also called the financial year or fiscal year for personal tax) begins on 6 April each year and ends on 5 April the following year. So the 2026/27 tax year runs from 6 April 2026 to 5 April 2027.
This is different from:
- Calendar year: 1 January to 31 December (used by most of the world)
- UK corporation tax accounting period: typically 12 months ending on a company's accounting reference date
- UK government financial year: 1 April to 31 March (used for public spending and budgets)
Why does the tax year start on 6 April?
The answer is a historical quirk from 1752. When Britain switched from the Julian calendar to the Gregorian calendar, 11 days had to be dropped to align with the rest of Europe. The Treasury refused to lose 11 days of tax revenue, so it pushed the tax year start from 25 March (the traditional "Lady Day") by 11 days to 5 April. In 1800, another leap-year adjustment moved it one more day to 6 April, where it has remained.
No other major economy uses 6 April. Most tax systems align with the calendar year (January) or the fiscal year (April 1 or July 1). The UK retains 6 April purely through institutional inertia.
What resets on 6 April
The start of each tax year is the most important financial date in the UK calendar. These allowances, thresholds and limits reset fresh on 6 April:
| What resets | 2026/27 amount |
|---|---|
| Personal Allowance | £12,570 |
| ISA annual allowance | £20,000 |
| Lifetime ISA bonus limit | £4,000/year (up to age 50) |
| Junior ISA allowance | £9,000 |
| Pension annual allowance | £60,000 (tapered for very high earners) |
| Capital Gains Tax annual exempt amount | £3,000 |
| Dividend allowance | £500 |
| Personal Savings Allowance | £1,000 / £500 / £0 by tax band |
| Marriage Allowance | Up to £252 tax saving |
If you have unused allowances on 5 April, you cannot carry them forward (with very limited exceptions, like pension carry-forward for up to 3 previous years). Use them or lose them.
Key tax year deadlines
31 January
Deadline for online self-assessment tax returns for the previous tax year. So the 2026/27 tax return is due by 31 January 2028. Any tax owed for 2026/27 must be paid by the same date, along with the first "payment on account" toward 2027/28 tax.
31 July
Second payment on account due (for self-assessed taxpayers).
31 October
Deadline for paper self-assessment tax returns for the previous tax year.
5 October
Deadline to register for self-assessment if this is your first year filing.
6 April
New tax year starts. All allowances reset. Any budget changes announced the previous autumn typically take effect now.
5 April
Tax year ends. Last day to use annual allowances (ISA, pension, CGT exempt amount, etc.) for the year.
What's new for 2026/27
The 2026/27 tax year continues the pattern of frozen thresholds set out in previous Autumn Budgets. Most headline numbers are unchanged:
- Personal Allowance: £12,570 (frozen since April 2021)
- Higher-rate threshold: £50,270 (frozen)
- Additional-rate threshold: £125,140 (frozen)
- ISA allowance: £20,000 (frozen since April 2017)
What changed going into 2026/27:
- National Living Wage: rose to £12.71/hour for over-21s (April 2026)
- Energy price cap: reduced in April 2026 (quarterly adjustments throughout the year)
- State Pension age: phased rise to 67 underway (affects those born between 6 April 1960 and 5 April 1961)
- Pension inheritance: inherited pensions expected to come into Inheritance Tax scope from April 2027 (announced in 2024 Autumn Budget)
See our full UK Tax Guide 2026/27 for the complete breakdown of every rate and threshold.
Fiscal drag: the hidden tax rise
When Chancellors freeze thresholds rather than raising them with inflation, the effect is a stealth tax rise. This is called fiscal drag. As nominal wages rise with inflation but thresholds don't, more workers are pulled into higher tax bands each year without any change in real (inflation-adjusted) earnings.
HMRC data shows the number of taxpayers paying higher-rate tax has approximately doubled since 2010, overwhelmingly due to threshold freezes rather than real wage growth. For 2026/27, fiscal drag continues — unless you got a pay rise above CPI, you're paying a slightly higher effective rate than last year.
Making the most of the new tax year
Use your ISA allowance early
Your £20,000 ISA allowance resets on 6 April. Using it early in the tax year (rather than rushing on 5 April) means your money is protected from tax for longer. Even one extra tax year of compound growth in an ISA is meaningful.
Top up your pension
If you haven't used your full pension annual allowance, the new tax year is a natural checkpoint. Pension contributions receive tax relief at your marginal rate — 20%, 40% or 45% — making them one of the most tax-efficient investments available. Carry-forward rules let you use unused allowances from up to the 3 previous tax years.
Use your CGT exempt amount
The Capital Gains Tax annual exempt amount is £3,000 for 2026/27. If you have investments sitting on unrealised gains, you can "bed and breakfast" them (sell and repurchase, respecting the 30-day rule) to crystallise gains within the allowance.
Check your tax code
Your tax code determines how much income tax your employer deducts from your salary. Codes are typically issued in March for the new tax year starting 6 April. If your code is wrong, you'll overpay or underpay tax — and fixing it now is easier than at year-end.
Frequently asked questions
When does the UK tax year start and end?
The UK tax year runs from 6 April to 5 April the following year. The 2026/27 tax year is from 6 April 2026 to 5 April 2027.
Is the UK tax year the same as the financial year?
For personal tax purposes, yes — the terms are used interchangeably. However, the UK government's financial year (used for budgets and public spending) runs from 1 April to 31 March, which is slightly different. Companies may also use different accounting reference dates for their own corporation tax.
Why doesn't the UK tax year start in January like other countries?
A historical quirk from the 1752 calendar switch from Julian to Gregorian. The Treasury didn't want to lose 11 days of tax revenue when the calendar realigned, so it moved the tax year start from 25 March by 11 days to 5 April (adjusted again in 1800 to 6 April). No policy reason — just institutional inertia.
What's the deadline for my self-assessment tax return?
31 January following the end of the tax year for online returns, 31 October for paper returns. For the 2026/27 tax year: online deadline is 31 January 2028, paper deadline is 31 October 2027.
Can I use last year's unused ISA allowance?
No. ISA allowances don't carry forward — unused allowance on 5 April is lost. The same applies to most annual allowances except pensions (where 3 years of carry-forward is permitted).
Are UK tax thresholds going up in 2026/27?
Most are frozen. Personal Allowance remains £12,570. Higher-rate threshold remains £50,270. ISA allowance remains £20,000. Current policy is to keep thresholds frozen until April 2028, creating fiscal drag as wages rise.
Quick links
- UK Tax Guide 2026/27 — full reference for every UK personal tax concept
- UK Income Tax Rates & Bands — the 20/40/45% breakdown
- UK Personal Allowance 2026/27 — £12,570 tax-free + the 60% taper trap
- UK Personal Savings Allowance — tax-free interest by band
- UK Income Tax Calculator — see your take-home for 2026/27
