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The Self Assessment deadline for the 2025/26 tax year is 31 January 2027. That is the last day to file your online tax return and pay any tax you owe for the year that ran from 6 April 2025 to 5 April 2026. If you send a paper return, the Self Assessment deadline is earlier, on 31 October 2026.
Missing the date costs money. HMRC charges a £100 penalty the day after the deadline, even if you owe no tax, and the fines grow the longer you leave it. This guide sets out every key date for 2025/26, who needs to file, a 12-point checklist to work through now, and what to do if you are running late.
Self Assessment deadline dates for 2025/26
These are the dates that matter for your 2025/26 tax return and the tax that goes with it.
| Date | What is due |
|---|---|
| 5 October 2026 | Register for Self Assessment if you are filing for the first time |
| 31 October 2026 | Paper tax return deadline |
| 30 December 2026 | File online by this date if you want tax under £3,000 collected through your PAYE tax code |
| 31 January 2027 | Online Self Assessment deadline, payment of the 2025/26 balance and your first payment on account for 2026/27 |
| 31 July 2027 | Second payment on account for 2026/27 |
| 31 January 2028 | Last day to amend your 2025/26 return |
If you missed the 5 October registration date, register straight away. It can take HMRC up to 10 working days to post your Unique Taxpayer Reference (UTR), and longer if you live abroad, so leaving it until January is risky.
Who needs to file a Self Assessment tax return?
You usually need to file a return for 2025/26 if any of these applied to you during the tax year:
- You were self-employed as a sole trader and earned more than £1,000 before expenses. This includes regular online selling, for example on eBay, Etsy or Vinted (see our guide to tax for online sellers).
- You were a partner in a business partnership.
- You received rental income above the £1,000 property allowance.
- You had untaxed income over £2,500, such as tips, commission or income from overseas.
- You had savings interest or dividends of more than £10,000.
- You made a capital gain you need to report, for example from selling a second home or shares.
- You or your partner received Child Benefit and one of you had income over £60,000, unless you pay the charge through your tax code.
- You need to claim tax relief on pension contributions as a higher or additional-rate taxpayer.
If you are not sure, HMRC has a free check if you need to send a Self Assessment tax return tool on GOV.UK.
Self Assessment deadline checklist: 12 things to do before 31 January
Work through this list now and you will have everything ready long before the Self Assessment deadline.
1. Find your UTR and Government Gateway login
Your UTR is a 10-digit number. You will find it on letters from HMRC, in your personal tax account and in the HMRC app. Check you can sign in to your Government Gateway account early, because resetting access can take several days.
2. Collect your employment documents
Gather your P60 for 2025/26, any P45 if you changed jobs and your P11D if you had benefits in kind such as a company car or private medical cover.
3. Total your self-employed income and expenses
Add up your sales and your allowable expenses for 6 April 2025 to 5 April 2026. Since basis period reform, sole traders are taxed on the profits of the tax year itself, so you no longer report an accounting year that ends part way through. Our self-employed tax calculator gives you a quick estimate of the tax and National Insurance on your profit.
4. Pull together rental income and costs
Landlords need total rent received, letting agent fees, repairs, insurance and mortgage interest. Mortgage interest is not deducted from rental profit. Instead you get a tax credit worth 20% of the interest.
5. List savings interest and dividends
Note interest from every bank and building society account. Your Personal Savings Allowance is £1,000 for basic-rate taxpayers, £500 for higher-rate taxpayers and nothing for additional-rate taxpayers. The dividend allowance for 2025/26 is £500, and dividends above it are taxed at 8.75%, 33.75% or 39.35%.
6. Work out any capital gains
If you sold shares, crypto or a property that was not your main home, calculate the gain. The annual exempt amount is £3,000. Gains above it are taxed at 18% or 24%, and Business Asset Disposal Relief was 14% for 2025/26. Use our capital gains tax calculator to check the figure.
7. Claim pension tax relief
Higher and additional-rate taxpayers can claim extra relief on personal pension contributions through the return. Many people miss this and overpay tax.
8. Add Gift Aid donations
Gift Aid donations extend your basic-rate band, which can reduce tax for higher-rate taxpayers. Keep a list of what you gave and to which charity.
9. Check the High Income Child Benefit Charge
If your income was between £60,000 and £80,000 and your household received Child Benefit, you will repay part of it. Above £80,000 you repay all of it.
10. Include student loan repayments
If you have a student loan and income above your plan’s threshold, the return works out any repayments still due.
11. Review your payments on account
If your income has fallen, you can ask HMRC to reduce your 2026/27 payments on account. Only do this if you are confident, because HMRC charges interest if you reduce them too far.
12. Plan how you will pay
You can pay by bank transfer, debit card or Direct Debit. If you cannot pay in full, you may be able to set up a Time to Pay arrangement online for debts up to £30,000, as long as your return is filed.
What happens if you miss the Self Assessment deadline?
HMRC’s penalties for a late 2025/26 return build up over time:
| How late | Penalty |
|---|---|
| 1 day | £100 fixed penalty |
| 3 months | £10 a day for up to 90 days (up to £900) |
| 6 months | 5% of the tax due or £300, whichever is higher |
| 12 months | Another 5% of the tax due or £300, whichever is higher |
Paying late adds separate penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months. HMRC also charges interest on late payments at the Bank of England base rate plus 4 percentage points, so even a short delay adds up.
If something serious stopped you meeting the deadline, such as a stay in hospital or a bereavement, you can appeal with a reasonable excuse. Busy periods and forgetting are not accepted.
How payments on account work
Payments on account are advance payments towards next year’s bill. You make them if your last Self Assessment bill was more than £1,000, unless more than 80% of your tax was already taken at source, for example through PAYE.
Here is a simple example. Say your 2025/26 bill is £3,000 and you have not paid anything yet. On 31 January 2027 you pay the £3,000 balance plus a first payment on account of £1,500 for 2026/27. On 31 July 2027 you pay a second £1,500. That first January can be a shock, so plan for it now.
Making Tax Digital: what changes after this return
Making Tax Digital for Income Tax started on 6 April 2026 for sole traders and landlords with qualifying income over £50,000. Your 2025/26 return is important because HMRC uses it to decide who joins next. If your self-employment and property income adds up to more than £30,000 before expenses, you are likely to need digital records and quarterly updates from April 2027.
Read our guide to Making Tax Digital for the self-employed to see what that means in practice.
Frequently asked questions
When is the Self Assessment deadline for 2025/26?
The online Self Assessment deadline for the 2025/26 tax year is 31 January 2027. Paper returns must reach HMRC by 31 October 2026. Any tax you owe for 2025/26 must also be paid by 31 January 2027.
What is the penalty for missing the Self Assessment deadline?
HMRC charges a £100 penalty as soon as your return is late, even if you owe no tax. After three months you pay £10 a day for up to 90 days, then further penalties of 5% of the tax due or £300 at six and 12 months.
Can I still register for Self Assessment after 5 October?
Yes. Register as soon as possible. HMRC can take up to 10 working days to send your Unique Taxpayer Reference, and you need it to file online before the 31 January Self Assessment deadline.
Where do I find my UTR number?
Your UTR is a 10-digit number shown on letters from HMRC, in your personal tax account on GOV.UK and in the HMRC app.
Do I have to pay my tax by the Self Assessment deadline?
Yes. The balance of your 2025/26 tax and your first payment on account for 2026/27 are both due by 31 January 2027. If you cannot pay in full, you may be able to set up a Time to Pay arrangement with HMRC.
Get help before the Self Assessment deadline
January is the busiest month of the year for accountants, so the earlier you start the better. Landlords in particular can benefit, as we explain in why filing your Self Assessment early could save landlords thousands. Cangaf’s ACCA and AAT qualified team in Bolton prepares and files Self Assessment tax returns for a fixed fee, checks you are claiming every allowance and tells you exactly what to pay and when.
Get a free quote or call us on 01204 859315 to get your 2025/26 return sorted well before 31 January 2027.
Related guides: Self-Assessment Accountants in Wigan: Why Sole Traders and Landlords Choose Local Support Over DIY Filing · Companies House ID Verification: What Actually Happens If You Miss the Deadline as a Director? · What Is A Self-Assessment Tax Return?
