Quick answer: For the 2025 to 2026 tax year, file your online Self Assessment return and pay what you owe by 11:59pm on 31 January 2027. A paper return had to reach HMRC by 31 October 2026. If you pay through your tax code, file online by 30 December 2026. Missing the return deadline costs a £100 penalty even if you owe nothing.
This guide follows HMRC’s Self Assessment deadlines page on GOV.UK, checked in October 2026. Dates can change, so confirm them there before you rely on them. To see what your January and July payments might be, try our payments on account calculator.
The dates for the 2025 to 2026 tax year
| What | Deadline |
|---|---|
| Register for Self Assessment (if new) | 5 October 2026 |
| Paper tax return received by HMRC | 31 October 2026 (this is closing now) |
| Online return, if you want the tax collected through your tax code | 30 December 2026 |
| Online tax return | 31 January 2027 |
| Pay the tax you owe for 2025 to 2026 | 31 January 2027 |
| Second payment on account, if you make them | 31 July 2027 |
The paper route is closing
A paper return must be received by HMRC by 31 October 2026, not just posted. If you miss it, you can still file online until 31 January 2027, so for most people the online route is the one that matters now.
Payments on account: the 31 January surprise
If you make payments on account, the 31 January bill is not just last year’s balance. It can include the balancing payment for 2025 to 2026 and the first payment on account towards 2026 to 2027, so the cash needed can be much larger than you expect. The second payment on account falls due on 31 July. Each payment on account is normally half of your previous year’s bill. Work out your own figures with our payments on account calculator.
What a missed deadline costs
- A late return means a £100 penalty even if you owe no tax.
- Tax paid late is charged interest, and further penalties build up the longer it stays unpaid.
- If you cannot pay in full, contact HMRC about a payment plan before the deadline.
How Making Tax Digital fits in
If you joined Making Tax Digital for Income Tax in April 2026, you send quarterly updates through the year, and that does not replace the 2025 to 2026 return due on 31 January 2027, which still follows the old rules. Check whether MTD applies to you with our MTD checker, and see the MTD penalties guide for how the new penalties work.
A simple plan for the next three months
- Now: gather income, expense and bank records for 6 April 2025 to 5 April 2026. Our spreadsheet maker can total them by category.
- November: log in to your HMRC online account and start the return rather than waiting for January.
- Before 30 December: file if you want any tax collected through your tax code.
- Before 31 January: file, then pay. Allow a few days for the payment to reach HMRC.
Altto is not affiliated with HMRC. This is general information, not tax advice.
Frequently asked questions
When is the Self Assessment deadline in January 2027?
Can I still file a paper Self Assessment return?
What is the penalty for filing late?
What are payments on account?
Does Making Tax Digital change the 31 January 2027 deadline?
Need tidy records before you file?
Make a free income and expense spreadsheet in your browser. No sign-up, nothing uploaded.
Sources
Check the dates and rules against HMRC’s own pages before you rely on them:
- GOV.UK — Self Assessment tax return deadlines
Altto is not affiliated with HMRC. This is general information, not tax advice.