The UK tax year doesn’t follow the calendar year. It runs from 6 April to 5 April — a date so unusual that most people don’t know why, and a date that drives every deadline in the UK tax system.
If you’re self-employed, a landlord, or file a Self Assessment, the tax year is the rhythm your financial life moves to. Allowances reset on 6 April. Your tax return covers the year that ended on the previous 5 April. Your payment deadlines fall on 31 January and 31 July. Getting these dates wrong triggers automatic penalties — even if you owe no tax.
This guide explains how the tax year works, what changed on 6 April 2026, every deadline you need to track, and why the whole system starts on such an odd date — with links to the detailed guides on this site for each topic that goes deeper.
1. The UK Tax Year: The Basic Framework
The UK tax year for Income Tax, National Insurance, and Self Assessment runs from 6 April to 5 April the following year. The current tax year — 2026/27 — runs from 6 April 2026 to 5 April 2027.
This is different from:
- The calendar year (1 January to 31 December) — used for most non-tax purposes
- The company accounting period — a limited company’s Corporation Tax period can be any 12-month period, set by its accounting reference date
- VAT quarters — set by HMRC when you register, and not aligned to the tax year
- The Scottish tax year — same dates (6 April to 5 April), but different income tax rates and bands
When you file a Self Assessment return, the return you file in early 2027 covers the 2025/26 tax year — the year that ended on 5 April 2026. This is the single most common source of confusion: the return you file in January 2027 covers income from April 2025 to April 2026, not from January to December 2026.
2. Why 6 April? (The 1752 Calendar Story)
The 6 April start date is a relic of a calendar change nearly 275 years ago.
Until 1752, England used the Julian calendar (established by Julius Caesar in 45 BCE), which was 11 minutes longer than the solar year. By the 18th century, this had accumulated into an 11-day drift from the calendars used by the rest of Europe, which had switched to the Gregorian calendar in 1582.
In September 1752, Britain caught up. The Calendar (New Style) Act 1750 dropped 11 days — people went to sleep on 2 September and woke up on 14 September. (There were riots, with people demanding “give us back our eleven days.”)
Historically, the tax year started on 25 March — Lady Day, one of the four quarter days when rents were due and contracts began. When the calendar shifted, taxpayers didn’t want to pay their taxes 11 days early. So the tax year end moved forward 11 days, from 24 March to 5 April.
Then in 1800, another day was added. The Julian calendar would have made 1800 a leap year, but the Gregorian calendar didn’t (century years aren’t leap years unless divisible by 400). The tax year moved one more day forward, to 6 April, where it has stayed ever since — even though 1900 was also a non-leap year in the Gregorian calendar, the government didn’t shift the date again.
The result: a tax year that starts on a date no one would choose today, but that’s too embedded in every system, contract, and software to change.
3. Key Dates and Deadlines in the 2026/27 Tax Year
Here’s the full calendar of dates that matter during 2026/27. The return you file during this tax year covers 2025/26 (the year that ended 5 April 2026).
Self Assessment deadlines (for the 2025/26 return)
| Deadline | Date | What you must do |
|---|---|---|
| Register for Self Assessment | 5 October 2026 | If you’re newly self-employed or need to file for the first time |
| Paper tax return | 31 October 2026 | HMRC must receive your paper return by this date |
| Tax coded out via PAYE | 30 December 2026 | File online by this date if you want a bill under £3,000 collected through your tax code |
| Online tax return | 31 January 2027 | Submit your 2025/26 return online |
| Balancing payment + first POA | 31 January 2027 | Pay your 2025/26 bill plus 50% of it as your first 2026/27 payment on account |
| Second payment on account | 31 July 2027 | Pay the remaining 50% towards your 2026/27 bill |
Other key dates during 2026/27
| Date | What happens |
|---|---|
| 6 April 2026 | 2026/27 tax year begins. New allowances take effect. Dividend tax rates increase. MTD for Income Tax starts for qualifying income over £50,000. |
| 5 April 2027 | Last day of 2026/27. Last day to use 2026/27 allowances (ISA, pension, CGT annual exempt amount, trading allowance, etc.) |
| 31 May 2027 | P60 must be issued to employees by employers |
| 6 July 2027 | P11D and P11D(b) deadline for employers (benefits in kind) |
For the full penalty regime if you miss any of these deadlines, see our Self Assessment penalties guide. If you’ve already missed the Self Assessment deadline, see our missed Self Assessment deadline action guide.
4. Payments on Account: The Two Dates That Catch People Out
Payments on account (POA) are advance payments towards your next tax bill — and they’re the deadline that catches most people by surprise.
If your Self Assessment tax bill exceeds £1,000 and less than 80% of your tax was collected at source (through PAYE, for example), HMRC requires you to make two payments on account each year:
| Payment | Due date | Amount |
|---|---|---|
| First POA | 31 January | 50% of your previous year’s tax bill |
| Second POA | 31 July | The remaining 50% |
On 31 January, you pay three things at once: your balancing payment (settling last year’s bill) plus your first payment on account (50% advance toward this year) — and if you had a second POA due the previous July, that’s already been collected.
Example: Your 2025/26 tax bill is £6,000. On 31 January 2027 you pay:
- £6,000 (balancing payment for 2025/26)
- £3,000 (first POA for 2026/27, = 50% of £6,000)
- Total: £9,000 on 31 January 2027
Then on 31 July 2027, you pay the remaining £3,000 (second POA for 2026/27).
If your income drops and you expect your next bill to be lower, you can apply to reduce your payments on account using form SA303 or through your HMRC online account. But if you reduce them too far and underpay, HMRC charges interest on the shortfall. For the full mechanics, see our payment on account explained guide. If you can’t cover the 31 July payment, see our can’t pay your payment on account guide.
5. What Changed on 6 April 2026
The 2026/27 tax year brought three significant changes:
Dividend tax increased by 2 percentage points
From 6 April 2026, the dividend ordinary rate (basic rate) increased from 8.75% to 10.75%, and the dividend upper rate (higher rate) from 33.75% to 35.75%. The additional rate stays at 39.35%. The £500 dividend allowance is unchanged. This affects anyone who takes dividends from a limited company — and is one of the reasons the tax gap between sole trader and limited company has narrowed. For the full comparison, see our sole trader or limited company guide.
Making Tax Digital for Income Tax started
From 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates to HMRC through MTD-compatible software. This replaces the annual Self Assessment return with a quarterly reporting cycle — though the payment deadlines (31 January and 31 July) don’t change. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028. For the full picture, see our Making Tax Digital guide and our MTD for income tax explained guide.
Employer NI secondary threshold at £5,000
The employer NI secondary threshold (the salary level above which employers pay 15% NI) remained at £5,000 for 2026/27, having been cut from £9,100 in April 2025. This affects limited company directors paying themselves a salary — the optimal salary is £12,570 (using the full Personal Allowance), but the company pays £1,135.50 in employer NI on it unless Employment Allowance applies. See our sole trader or limited company guide for the full director salary analysis.
What didn’t change
- Personal Allowance: £12,570 — frozen until April 2031
- Basic rate limit: £37,700 — frozen until April 2031
- Higher rate threshold: £50,270 (£12,570 + £37,700) — frozen until April 2031
- Additional rate threshold: £125,140 — unchanged
- Class 4 NI for sole traders: 6% on profits £12,570–£50,270, 2% above — unchanged from 2025/26
- ISA limit: £20,000 — unchanged for 2026/27
- Dividend allowance: £500 — unchanged
- CGT annual exempt amount: £3,000 — unchanged
- Pension annual allowance: £60,000 — unchanged
For the full breakdown of how the frozen Personal Allowance creates fiscal drag and the £100,000 taper trap, see HMRC’s income tax rates and allowances and our Personal Tax Allowance 2026 guide.
6. Allowances That Reset on 6 April
Most annual allowances operate on the tax year cycle — they reset on 6 April and any unused portion is lost. Use them before 5 April or lose them for that year.
| Allowance | 2026/27 amount | What it covers |
|---|---|---|
| Personal Allowance | £12,570 | Tax-free income (tapers above £100,000) |
| ISA limit | £20,000 | Tax-free savings and investments |
| Dividend allowance | £500 | Tax-free dividend income |
| Trading allowance | £1,000 | Tax-free self-employment / misc income |
| Property allowance | £1,000 | Tax-free property / rental income |
| CGT annual exempt amount | £3,000 | Tax-free capital gains |
| Pension annual allowance | £60,000 | Tax-relieved pension contributions |
| Marriage Allowance transfer | £1,260 | Transferable Personal Allowance between spouses (saves up to £252) |
| Blind Person’s Allowance | £3,250 | Additional tax-free allowance (on top of Personal Allowance) |
| Personal Savings Allowance | £1,000 (basic rate) / £500 (higher rate) | Tax-free savings interest |
The 5 April deadline matters. If you’re planning to use your ISA allowance, make a pension contribution, or realise a capital gain within the annual exempt amount, you must do it before 5 April 2027 for it to count against 2026/27 allowances. After that, the allowance is gone.
For how pension contributions reduce your adjusted net income and can restore a tapered Personal Allowance, see our pension contributions and Self Assessment guide. For Marriage Allowance specifically, see our Marriage Allowance for sole traders guide.
7. Tax Year vs Accounting Period vs VAT Quarter
The tax year is just one of several periods that affect your tax obligations. If you’re a sole trader with VAT and MTD, you may be tracking three different cycles simultaneously.
Tax year (6 April – 5 April): Used for Income Tax, National Insurance, Self Assessment, and most personal allowances. Under MTD for Income Tax, quarterly updates are sent within this cycle (deadlines: 7 August, 7 November, 7 February, 7 May).
VAT quarters: Set by HMRC when you register for VAT. Your VAT Return is due one month and seven days after each quarter ends. VAT quarters are not aligned to the tax year — they can start in any month. If you’re VAT-registered, you file VAT Returns on a separate cycle to your Self Assessment.
Company accounting period: A limited company’s Corporation Tax return (CT600) covers its accounting period, which is usually 12 months ending on the company’s accounting reference date. This can be any date — it doesn’t have to align with the tax year. The company files its annual accounts with Companies House on a separate deadline too.
PAYE: If you have employees (or you’re a company director on payroll), PAYE operates on a tax-year cycle. Tax codes are updated each 6 April, P60s are issued by 31 May, and P11Ds by 6 July.
The practical implication: if you’re a VAT-registered sole trader with MTD for Income Tax, you have three separate reporting cycles running in parallel — VAT quarters, MTD quarterly updates, and (if applicable) your Self Assessment final declaration. Each has its own deadlines and penalty regime. For the full MTD reporting cycle, see our MTD quarterly updates guide.
8. What to Do Before 5 April (Year-End Planning)
The days before 5 April are your last chance to use 2026/27 allowances. Here’s the checklist:
Pension contributions: If you want to reduce your 2026/27 adjusted net income — to avoid the £100,000 Personal Allowance taper or to stay below a tax band threshold — make personal pension contributions before 5 April 2027. Contributions are deducted from your adjusted net income and get tax relief at your highest rate. See our pension contributions and Self Assessment guide.
ISA top-ups: Use your full £20,000 ISA allowance before 5 April. Unused allowance doesn’t roll forward — it’s lost for that tax year.
Capital gains: If you have investments to sell, use your £3,000 CGT annual exempt amount before 5 April. If you have gains exceeding the allowance, consider “bed and ISA” — selling outside an ISA and repurchasing inside it to shield future gains.
Gift Aid donations: Like pension contributions, charitable donations made before 5 April reduce your adjusted net income for that tax year, which can help with the £100,000 taper.
Trading and property allowance: If your self-employment or rental income is under £1,000, you don’t need to declare it — but if it’s over £1,000, make sure you’ve registered for Self Assessment by the following 5 October.
MTD check: If you’re a sole trader or landlord with qualifying income approaching £50,000, check whether you’ll be brought into MTD for Income Tax from the following April. See our MTD qualifying income thresholds guide.
For the full set of ways to reduce your tax bill — expenses, allowances, pensions, Gift Aid, and the order to pull the levers — see our reduce your Self Assessment tax bill hub.
9. What to Do After 6 April (New Year Checklist)
The start of a new tax year on 6 April is the time to set up for the next 12 months:
Check your tax code: If you’re employed, your employer should receive an updated tax code from HMRC. Check your first payslip to make sure it’s correct — a wrong code means you’re paying the wrong amount all year. See our tax code guide and our check your tax code guide.
Register for Self Assessment if you’re new: If you became self-employed or started earning untaxed income during 2026/27, you must register by 5 October 2027. See our first-year self-employed checklist.
Set up MTD software if you’re newly in scope: If your qualifying income crossed £50,000 in 2025/26, you need MTD-compatible software from 6 April 2026. Free options exist — see our cheapest MTD software for sole traders guide.
Start digital records from day one: If you’re in MTD for Income Tax, your digital record-keeping starts on 6 April. Don’t wait — the first quarterly update deadline is 7 August. See our MTD quarterly updates guide.
Review your business structure: The new tax year is a natural point to review whether sole trader or limited company is still the right structure — especially given the 2026/27 changes. See our sole trader or limited company guide.
10. Scottish Tax Year: Same Dates, Different Rates
The Scottish tax year uses the same dates (6 April to 5 April), but Scotland has its own Income Tax rates and bands for non-savings, non-dividend income. The Scottish bands for 2026/27 have small threshold changes but the same number of bands.
If you live in Scotland, your Income Tax on employment income and self-employment profits is calculated using Scottish rates. Savings income and dividend income still use the UK-wide rates. Your tax code will start with an “S” to indicate Scottish rates apply. For issues with Scottish tax codes, see our Scottish tax code wrong address guide.
The Bottom Line
- The tax year runs 6 April to 5 April — a quirk from the 1752 calendar change that’s too embedded to fix. The 2026/27 tax year runs from 6 April 2026 to 5 April 2027.
- The return you file in January 2027 covers 2025/26 — the year that ended 5 April 2026. This is the most common source of tax-year confusion.
- Three key deadlines: online filing and balancing payment + first POA on 31 January, second POA on 31 July, and registration by 5 October if you’re new.
- Three changes on 6 April 2026: dividend tax up 2 points (10.75%/35.75%), MTD for Income Tax for qualifying income over £50,000, and employer NI from £5,000.
- Allowances reset on 6 April — use your ISA, pension, CGT, and dividend allowances before 5 April or lose them for that tax year.
- The Personal Allowance is frozen at £12,570 until April 2031 — fiscal drag means more income is pulled into tax and into the higher band each year.
- You may be tracking three cycles at once — the tax year (Self Assessment/MTD), VAT quarters, and (for companies) the accounting period. Each has its own deadlines.
Start with our Making Tax Digital guide if you’re newly in scope for MTD, or our reduce your Self Assessment tax bill hub if you want to plan your year-end allowances. If you’ve missed a deadline, go straight to our missed Self Assessment deadline guide — the earlier you act, the less it costs. New to self-employment? Our starting out guide explains what you need to do and when. For the full picture in one place, browse our complete Self Assessment guide — or if you’d rather have someone handle it, compare your options in Self Assessment help.