Quick answer
The Self Assessment deadline for the 2025/26 tax year is 31 January 2027 for both online filing and paying tax owed. File well before Christmas to avoid the busiest HMRC period, and pay early so bank delays do not make you late.
Updated October 2026 · Figures based on 2026/27 rates
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October and November
Gather records, check your UTR works and download statements. If you are new, register now and wait for your activation code.
December
Prepare the return, claim expenses, check pension and Gift Aid details, and file early so you know the bill in good time.
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January
Pay by mid-January using the correct payment reference. Faster Payments usually clear the same day, but allow extra time.
If you will be late
File as soon as possible and contact HMRC about a payment plan. Penalties start the day after the deadline.
The dates that matter for the 2025/26 return
The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. Its online return and any balancing payment are due by 31 January 2027. That same date is also when the first payment on account for 2026/27 falls due if you are in the payments on account system, and the second instalment follows on 31 July 2027. The deadline to register for Self Assessment, 5 October 2026, has already passed, and the deadline for paper returns, 31 October 2026, is close. If you missed registration, our guide to registering after 5 October explains what to do next. GOV.UK’s Self Assessment tax returns guide confirms these deadlines.
| Date | What happens |
|---|---|
| 5 October 2026 | Registration deadline for new filers for 2025/26 |
| 31 October 2026 | Paper return deadline |
| 31 January 2027 | Online return, balancing payment and first payment on account |
| Early March 2027 | 5% charge applies to tax still unpaid 30 days after the deadline |
| 31 July 2027 | Second payment on account |
A week-by-week plan from now
- This week. Check you can log in to your Government Gateway account and that your UTR and National Insurance number are to hand.
- By the end of October. Collect income records, bank statements, CIS statements, dividend vouchers and pension payment details.
- November. Total your expenses by category, and note any one-off items such as equipment or vehicle costs.
- December. Complete the return or hand your figures to your accountant, and review the calculation.
- Early January. File, then arrange payment so that it clears before the deadline.
Filing early does not bring the payment date forward. The money is still due on 31 January, but you will know the exact amount in good time. Our pre-filing checklist sets out the documents you should gather.
Worked example: how much will leave your account on 31 January 2027
This is an illustrative example. A sole trader’s 2024/25 tax bill was £4,000, so payments on account for 2025/26 were £2,000 each, paid on 31 January and 31 July 2026. When the 2025/26 return is completed, the final bill is £5,000.
| Item | Working | Amount |
|---|---|---|
| Final 2025/26 bill | From the return | £5,000 |
| Less payments on account already made | £2,000 + £2,000 | £4,000 |
| Balancing payment due 31 January 2027 | £5,000 – £4,000 | £1,000 |
| First payment on account for 2026/27 | £5,000 / 2 | £2,500 |
| Total due on 31 January 2027 | £1,000 + £2,500 | £3,500 |
| Second payment on account, 31 July 2027 | Half of £5,000 | £2,500 |
Many people are surprised by the size of the January payment because it combines a balancing payment with the first instalment of next year’s bill. Setting money aside each month avoids a cash flow squeeze; see how to save for your self-employed tax bill and payments on account explained.
What happens if you miss the deadline
A late online return attracts a £100 penalty immediately, even if no tax is due. After three months, daily penalties of £10 start, up to a maximum of £900. At six and twelve months, a further penalty of 5% of the tax due, or £300 if higher, applies. Paying late adds charges of 5% of the unpaid tax at 30 days, six months and twelve months, plus interest at Bank Rate plus 4%. Read what happens if you miss the deadline and late payment penalties explained for more detail. If you cannot pay in full, contact HMRC early, as Time to Pay arrangements are generally available for debts under £30,000.
Common mistakes
- Leaving everything until the last week of January when HMRC services are busiest.
- Forgetting that the January payment may include the first payment on account.
- Not having a Government Gateway login ready, as the activation code can take time to arrive.
- Missing records for CIS, dividends or foreign income.
- Paying late because of bank transfer timing.
Final preparation checklist
- Login details and UTR located.
- Income and expenses totalled for 6 April 2025 to 5 April 2026.
- Tax bill estimated and funds set aside.
- Payment method chosen and made with enough time to clear.
- A copy of the return and calculation saved.
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This article is general information, not personal tax advice.
Frequently asked questions
Can I file before the tax year ends?
You can file once the tax year has ended on 5 April, from 6 April onward.
What if 31 January falls on a weekend?
The deadline stays the same, so plan to pay and file earlier.
Can I file my return before 31 January 2027 and pay later?
You can file any time after the tax year ends on 5 April, but payment is still due by 31 January 2027. Filing early simply tells you the amount sooner so you can plan.
What if I cannot afford to pay on 31 January?
Contact HMRC as soon as possible. Time to Pay arrangements are generally available for debts under £30,000, though interest still applies. Filing on time avoids the separate late filing penalties.
Do I need to file if I earn under the personal allowance?
You might not owe tax, but you may still need to file, for example if you are self-employed above the trading allowance or have other reportable income. Check current HMRC guidance.
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The Bottom Line
The 31 January 2027 deadline covers your 2025/26 online return, the balancing payment and the first payment on account for 2026/27 — so the amount leaving your account can be much larger than the tax bill alone. Work backwards from the deadline: gather records by November, file in December, and pay by mid-January so bank delays do not make you late.
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