UK Tax Year 2026/27: A Checklist of Key Money Dates and Deadlines

UK Tax Year 2026/27: A Checklist of Key Money Dates and Deadlines

The UK tax year refuses to line up with the calendar. It opens on 6 April 2026 and closes on 5 April 2027, so the deadlines that matter are scattered across a year that begins in spring and ends in spring. Miss the important ones and the cost is concrete: penalties, interest, and allowances that vanish because they cannot be carried forward. What follows is a working calendar for 2026/27 — the dates worth saving to your phone now, and the job each one expects of you.

6 April 2026: the year's reset button

Everything refreshes: your ISA allowance, your capital gains exemption, your pension headroom. Most of it is use-it-or-lose-it, which means the first day of the tax year is not a filing deadline but a planning deadline. The allowances you do not use by 5 April 2027 do not roll over into the next year. They simply disappear.

For 2026/27, the headline numbers are likely to remain familiar. The personal allowance is £12,570. The basic-rate band is £37,700. The ISA allowance is £20,000. The capital gains tax annual exempt amount is £3,000. The dividend allowance is £500. The pension annual allowance is £60,000 for most people, with a tapered allowance for high earners and a £10,000 money purchase annual allowance for those who have flexibly accessed their pension. The inheritance tax annual exemption is £3,000.

• ISA allowance: £20,000. Use it or lose it.
• Capital gains tax exemption: £3,000 of gains before tax.
• Pension annual allowance: £60,000, subject to taper and carry-forward rules.
• Dividend allowance: £500 of dividends before tax.
• Inheritance tax annual exemption: £3,000 per person, plus any unused amount from the previous year.

If you have £20,000 sitting in a savings account earning interest that will be taxed, moving it into an ISA on 6 April 2026 gives it a full year of tax-free growth. Wait until 5 April 2027 and you still get the allowance, but you have lost almost twelve months of shelter. The same logic applies to pension contributions: a £10,000 contribution made early in the tax year has longer to grow before you need it.

19 April 2026: final PAYE and NICs for 2025/26

If you are an employer, this is the day the final PAYE and National Insurance contributions for the 2025/26 tax year are due. If you pay electronically, you usually have until 22 April 2026. This is not a date for employees, but it is worth knowing if you run payroll: late payment triggers interest and potentially penalties, and HMRC can require a security deposit if you are persistently late.

31 May 2026: P60 deadline

Employers must give every employee a P60 by 31 May 2026. The P60 summarises pay and tax for the 2025/26 year. If you are employed, check yours. It is the document mortgage lenders, tax credit claimants, and HMRC ask for. If you have more than one job, you should receive a P60 from each employer. If your P60 looks wrong, query it now — not in January when you are trying to file a return.

6 July 2026: P11D and benefits in kind

Employers must file P11D and P11D(b) forms for 2025/26 by 6 July 2026. These report benefits in kind: company cars, private health insurance, interest-free loans, and similar perks. Employees should check the P11D too. A benefit that is reported incorrectly can change your tax code, and a benefit that is missed can lead to an unexpected bill later. Class 1A National Insurance on these benefits is due by 19 July 2026, or 22 July if paid electronically.

31 July 2026: second payment on account

If you file a self-assessment return and your tax bill is more than £1,000, you usually make payments on account. The second payment for the 2025/26 tax year is due on 31 July 2026. For example, if your 2024/25 tax bill was £10,000, you will have paid £5,000 on 31 January 2026 and another £5,000 on 31 July 2026. Missing this date means interest starts running immediately. If your income has dropped, you can ask HMRC to reduce your payments on account — but do it before the deadline, not after.

5 October 2026: register for self-assessment

This is one of the most commonly missed deadlines. If you have income or gains that need to be reported for the 2025/26 tax year and you are not already in self-assessment, you must tell HMRC by 5 October 2026. That includes new freelance or side-hustle income, rental income, crypto gains, share sales above the allowance, and dividends above the allowance. The penalty for failing to notify HMRC is based on the tax due, so it can be far more than the £100 late-filing penalty. If you are unsure, check GOV.UK or speak to an accountant. Registering early also gives you time to gather records.

31 October 2026: paper return deadline

If you file a paper self-assessment return for 2025/26, it must reach HMRC by 31 October 2026. Most people file online, but if you prefer paper, this is your deadline. Miss it and you can still file online by 31 January 2027, but you cannot avoid the late-filing penalty if you were required to file and missed the paper date. The online system is usually more forgiving, but it is not a free extension for paper filers.

30 December 2026: the coding-out deadline

If you want HMRC to collect the tax you owe for 2025/26 through your PAYE code in 2027/28, you must file your online return by 30 December 2026. This only works if the tax owed is less than £3,000 and you have enough PAYE income. It is a useful option because it spreads the cost across the year. Miss 30 December and you will need to pay by 31 January 2027 instead.

31 January 2027: the big one

This is the deadline most people know. By 31 January 2027 you must file your online self-assessment return for 2025/26, pay any balancing payment for 2025/26, and make your first payment on account for 2026/27. If you miss it, the penalties stack up:

• Late filing: £100 immediately, even if you owe no tax.
• After three months: £10 per day, up to £900.
• After six months: £300 or 5% of the tax due, whichever is greater.
• After twelve months: another £300 or 5% of the tax due.
• Late payment: 5% of the unpaid tax at 30 days, another 5% at six months, and another 5% at twelve months.

Interest is added daily on top. Suppose you owe £8,000 and file three months late. You pay the £100 penalty, £900 in daily penalties, and interest from the original due date. If you cannot pay, call HMRC before 31 January. They can often set up a payment plan, and doing that early can reduce the damage.

5 April 2027: use it or lose it

The final day of the 2026/27 tax year is your last chance to use the allowances that do not carry forward. That means topping up your ISA, making pension contributions, realising capital gains up to the £3,000 exemption, using your inheritance tax annual exemption, and making charitable donations if you want Gift Aid for the year. If you are married or in a civil partnership, check whether you can transfer the marriage allowance. If you have children, check junior ISA and child benefit rules. The tax year ends at midnight on 5 April 2027. The new year begins the next day.

A month-by-month quick list

1. 6 April 2026: New tax year. Allowances reset.
2. 19/22 April 2026: Final PAYE and NICs for 2025/26.
3. 31 May 2026: P60s to employees.
4. 6 July 2026: P11D and P11D(b) for 2025/26.
5. 19/22 July 2026: Class 1A NICs due.
6. 31 July 2026: Second payment on account for 2025/26.
7. 5 October 2026: Register for self-assessment if newly required.
8. 31 October 2026: Paper self-assessment return deadline.
9. 30 December 2026: Online return deadline to code out tax owed under £3,000.
10. 31 January 2027: Online return, balancing payment, first payment on account.
11. 5 April 2027: End of tax year. Use allowances.
12. 6 April 2027: New tax year begins.

Who needs to diarise what?

If you are employed

Your key dates are 31 May 2026 for your P60 and 6 July 2026 for any P11D. If you have a side hustle, rental income, or investment gains, 5 October 2026 is your registration deadline. Use your ISA and pension allowances before 5 April 2027. Check your tax code when it arrives, especially if you have changed jobs or received a benefit in kind.

If you are self-employed

Your year is shaped by 31 July 2026 and 31 January 2027 for payments on account. If you are new to self-assessment, register by 5 October 2026. File online by 31 January 2027 unless you file on paper, in which case 31 October 2026 is your deadline. Keep records of income and expenses as you go. A shoebox of receipts in January is a penalty waiting to happen.

If you are retired or have investments

Watch 5 April 2027 for ISA, capital gains, pension, and inheritance tax allowances. If you are drawing from a pension, check the money purchase annual allowance if you have flexibly accessed it. If you have shares, funds, or property, consider whether to realise gains before the end of the tax year. The annual exempt amount is only £3,000, so it does not take much to exceed it.

Penalties and interest: the cost of forgetting

HMRC does not treat missed deadlines as administrative oversights. It treats them as debts. The penalties are designed to be noticed. A late self-assessment return starts at £100. If you are three months late, the daily penalties begin. If you are six months late, HMRC adds a percentage of the tax. If you are twelve months late, it can add another percentage. Late payment penalties are separate and are charged at 30 days, six months, and twelve months. Interest runs daily from the due date until the tax is paid.

There is also the quieter cost: allowances you cannot recover. If you miss the ISA deadline, you cannot backdate a contribution. If you miss the pension annual allowance, you may be able to use carry-forward from previous years, but only if you have unused allowance and you act in time. If you miss the capital gains exemption, the gain is taxable. The tax system rewards people who plan and penalises people who put things off.

Deadlines are not suggestions. In the UK tax system, a date missed is usually a bill increased.

Final thought: put the dates in now

Set calendar reminders two weeks before each date. Put 31 January 2027 and 5 April 2027 in your phone with alerts. If you use an accountant, agree a timetable for sending records. If you file yourself, start gathering documents in March or April, not January. The tax year 2026/27 runs from 6 April 2026 to 5 April 2027. The dates are fixed. The only variable is how much they cost you.

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