Last updated: 14 October 2026
What happens if you miss the Self Assessment filing deadline?
Around a million people miss the 31 January online filing deadline each year, according to HMRC’s figures, and each one gets an automatic £100 penalty, even if no tax is owed. The penalties rise the later you are: daily penalties of £10 a day after 3 months (up to £900), then further penalties at 6 and 12 months. Interest and late payment penalties apply separately to any tax paid late. File as soon as you can, because penalties keep growing.
Self Assessment late filing penalties
| How late | Penalty |
| 1 day | £100 |
| 3 months | £10 a day for up to 90 days (maximum £900) |
| 6 months | £300 or 5% of the tax due, whichever is higher |
| 12 months | Another £300 or 5% of the tax due, whichever is higher; more if information was deliberately withheld |
Late payment penalties and interest
| How late | Penalty |
| 30 days | 5% of unpaid tax |
| 6 months | A further 5% |
| 12 months | A further 5% |
Interest is charged on unpaid tax from the due date at the Bank of England base rate plus 4%.
Key dates
- 5 October: register for Self Assessment if you’re new to it
- 31 October: paper returns
- 30 December: online returns, if you want tax under £3,000 collected through your tax code
- 31 January: online returns and paying the balance and first payment on account
- 31 July: second payment on account
Reasonable excuse
You can appeal if you have a reasonable excuse, such as serious illness, bereavement, a fire or flood, or HMRC’s systems failing. Appeal within 30 days of the penalty notice. Forgetting, or relying on someone else who let you down, is usually not enough.
Example
Dan files his 2025/26 return on 15 May 2027, three and a half months late, and owes £2,000. He gets the £100 penalty, plus daily penalties from 1 May to 15 May (15 days, £150). He pays the tax on 15 May, so he also owes 5% late payment penalty (£100) and interest. In total, he pays about £350 plus interest on top of his tax.
If you no longer need to file
If HMRC sent you a notice to file but your circumstances have changed, tell HMRC. It may withdraw the notice and cancel penalties.
Tips
- Gather documents early: P60, P11D, bank interest, rental and self-employed records
2. Register for the HMRC app to check your figures
3. File early and pay later, if you need time to pay
4. Set up a payment plan if you owe up to £30,000
Partnerships and trustees
Partnership returns have their own penalties: each partner gets the £100 penalty if the partnership return is late. Trustees face the same penalty structure as individuals.
Frequently asked questions
Do I get a penalty if I owe no tax?
Yes, the £100 late filing penalty applies anyway.
Can I pay in instalments?
Yes, through an online payment plan if you owe £30,000 or less.
Will HMRC remind me?
HMRC sends reminders, but you’re still responsible.
Can an accountant file late for me?
Yes, the sooner the better.
Related: paying Self Assessment and registering as a sole trader.
Talk to Accotax
Want this handled for you? Our team at Accotax can help with Self Assessment deadlines. See our tax return accountants service, or contact us for a free, no-obligation quote.
This page is general guidance based on HMRC rules for the 2026/27 tax year, checked against gov.uk on 14 October 2026. It is not personal advice, so speak to an accountant about your own situation.
