Self Assessment Tax Return UK 2025/26 — Deadline, Who Must File & How to File
If you were self-employed, a landlord, or had other untaxed income in the UK last year, your Self Assessment tax return is probably due soon. This guide explains the deadline, who must file, what you need, and how to file — in plain English.
The deadline: 31 January 2027
Your online Self Assessment return for the 2025/26 tax year must reach HMRC by midnight on 31 January 2027. Any tax you still owe for that year must also be paid by the same date.
The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. So the return due in January 2027 covers income from the tax year that has already finished — not the year you are living in now.
Three things fall due on 31 January 2027:
- Your online tax return for 2025/26.
- Your balancing payment — the tax you still owe for 2025/26.
- Your first payment on account for 2026/27 — if one applies to you. This is usually half of your previous year’s bill, and it catches many people by surprise.
Two earlier dates have already passed: the deadline to register for Self Assessment for the first time was 5 October 2026, and paper returns had to be filed by 31 October 2026. If you missed those, file online now — do not wait for January.
Who must file a Self Assessment return?
You usually need to file if, during 2025/26, any of these applied to you:
- You were self-employed as a sole trader and earned more than £1,000 from self-employment.
- You were a partner in a business partnership.
- You earned income from renting out property.
- You had other untaxed income, for example from tips, commission, or selling goods online.
- You received income from abroad that needs to be declared.
- Your income was over £100,000, even if your tax was taken through PAYE.
- HMRC sent you a notice to file a return.
If HMRC sent you a notice to file, you must file even if you think you owe nothing. If you are not sure, use the free checker on GOV.UK — search “Check if you need to send a Self Assessment tax return”.
What happens if you miss the deadline?
The penalty starts immediately:
- £100 straight away, even if you file one day late — even if you owe no tax at all.
- £10 a day after three months late, up to 90 days.
- 5% of the tax owed at six months late, and another 5% at 12 months late.
- Separate penalties apply for paying late: 5% of unpaid tax at 30 days, six months, and 12 months late, plus interest.
Filing late and paying late are two different penalties. If you cannot pay in full, file on time anyway and ask HMRC about a Time to Pay arrangement.
How much tax will you pay? The 2025/26 rates
For England, Wales and Northern Ireland, the Personal Allowance for 2025/26 is £12,570 — the amount you can earn before you pay Income Tax. It is frozen at that level and is the same for 2026/27.
After the allowance, taxable income is taxed at:
| Income (after allowance) | Rate |
|---|---|
| Up to £37,700 (total income up to £50,270) | 20% basic rate |
| £37,701 to £125,140 | 40% higher rate |
| Over £125,140 | 45% additional rate |
If your adjusted net income is over £100,000, your Personal Allowance reduces by £1 for every £2 over £100,000, until it disappears completely at £125,140. Scotland sets its own Income Tax bands, so check the Scottish rates if you live there.
What you need before you file
Gather these before you start:
- Your Unique Taxpayer Reference (UTR) — the 10-digit number HMRC gave you when you registered.
- Your Government Gateway user ID and password.
- Your income records for 6 April 2025 to 5 April 2026: invoices, bank statements, P60/P45 if you were also employed, and rental income records.
- Your allowable expenses: business costs, office costs, travel, and other costs you can claim. Keep receipts and records for at least five years after the 31 January deadline.
- Details of any pension contributions, Gift Aid donations, and student loan repayments.
If you do not have a UTR yet, register for Self Assessment first. It can take time for the UTR to arrive by post, so do not leave this until January.
How to file online, step by step
- Sign in to HMRC’s Self Assessment service on GOV.UK, or use commercial tax software.
- Tell HMRC about your income — employment, self-employment, property, savings, and any other income.
- Enter your allowable expenses and claim the reliefs you are entitled to.
- Check the calculation HMRC shows you before you submit.
- Submit your return and keep the submission receipt.
- Pay what you owe by 31 January 2027 — filing and paying are separate steps. Paying through your bank, by debit card, or through your HMRC online account are common options.
You can file from 6 April 2026. Filing early does not mean you pay early — the payment deadline stays 31 January 2027.
One warning for 2025/26: this return decides your Making Tax Digital start date
Making Tax Digital (MTD) for Income Tax is already live. Sole traders and landlords with qualifying income over £50,000 had to use it from 6 April 2026. From 6 April 2027 it extends to qualifying income over £30,000 — and HMRC decides that from your 2025/26 return.
Qualifying income is your gross income from self-employment and property, before expenses are taken off. Wages, dividends, pensions and partnership income do not count towards it. If your 2025/26 total is over £30,000, plan now for digital records and quarterly updates from April 2027. (From 6 April 2028 the threshold falls to £20,000.)
Your November checklist
- Check whether you need to file — use the GOV.UK checker if unsure.
- Make sure you have your UTR and Government Gateway login.
- Gather income and expense records for 6 April 2025 to 5 April 2026.
- Work out your allowable expenses — do not guess.
- File before Christmas if you can, so January is not a rush.
- Set money aside for the balancing payment and the first payment on account.
Frequently asked questions
When is the Self Assessment deadline for 2025/26?
31 January 2027, for your online return and for paying the tax you owe.
Can I still file if I missed the 5 October 2026 registration deadline?
Yes — register now. If HMRC sends you a notice to file, you normally have three months from the date on that letter to submit, but interest on any tax owed still runs from 31 January 2027.
What is the penalty for filing late?
£100 immediately, even if you owe no tax. Daily penalties of £10 start after three months, and further penalties apply at six and 12 months.
Do I need to file if I earned less than £1,000 from self-employment?
Usually no — there is a £1,000 trading allowance. But you must still file if HMRC sent you a notice to file, or if you have other reasons to file, such as rental income or income over £100,000.
Does Making Tax Digital change my 2025/26 return?
No. Your 2025/26 return is filed in the normal way by 31 January 2027. MTD affects how you report from the tax year in which you join — 2026/27 if you were already in scope, or 2027/28 if you join at the £30,000 threshold.
This article gives general information about UK tax, not personal financial or tax advice. Tax rules can change, and your situation may be different. Check GOV.UK or speak to a qualified accountant before you act.
