Self Assessment late filing penalties: how the £100 penalty grows
A late tax return costs £100 the day after the deadline, even if you owe nothing. Leave it longer and the penalties stack up. Here's how GOV.UK says they build, with worked examples.
Checked against GOV.UK on 23 October 2026. General information for sole traders in England, Wales and Northern Ireland, not tax advice. Scottish Income Tax rates are different.
The late filing penalties
| How late | Penalty |
|---|---|
| 1 day | £100 fixed penalty |
| 3 months | £10 a day, for up to 90 days (maximum £900) |
| 6 months | 5% of the tax due or £300, whichever is greater |
| 12 months | Another 5% of the tax due or £300, whichever is greater |
For the 2025/26 online return, "late" means after 31 January 2027. These are for filing late. Paying late has its own penalties and interest on top: see late payment penalties and interest.
Worked examples
No tax to pay, filed 2 weeks late: £100. It applies even if you owe nothing or are due a CIS refund.
£2,000 tax due, filed 7 months late: £100 + £900 + £300 = £1,300. The 6-month charge is £300 because 5% of £2,000 is only £100, and the rule takes whichever is greater.
£10,000 tax due, filed 7 months late: £100 + £900 + £500 (5% of £10,000) = £1,500.
HMRC has a penalty estimator for your own figures.
Why CIS subbies get caught
Many subcontractors are owed money back after 20% CIS was taken all year, so it's easy to think there's no rush. But the £100 penalty still applies, and filing late delays your refund. See getting a CIS refund through Self Assessment.
Stop the clock
The daily and percentage penalties only build while the return is outstanding, so file as soon as you can. If something serious stopped you, you may be able to appeal: see how to appeal a penalty. The January tax bill calculator shows what you'll owe.
This guide is part of our Self Assessment guides for the self-employed.
Free: The UK Contractor's Cheat Sheet 2026/27
CIS rates, overtime maths, tax dates, mileage, VAT and late payment, on 2 pages. Keep it on your phone or print it for the van.
Frequently asked questions
Is there a penalty if I owe no tax?
Yes. The £100 late filing penalty applies even if you owe nothing.
What is the maximum daily penalty?
£10 a day for up to 90 days, so £900, starting 3 months after the deadline.
Do late filing and late payment penalties both apply?
Yes. They're separate, and interest is charged on unpaid tax as well.
Can I get a penalty cancelled?
You can appeal if you had a reasonable excuse, usually within 30 days of the penalty date.
Sources
- Self Assessment tax returns: penalties – GOV.UK
- Estimate your penalty for late Self Assessment tax returns and payments – GOV.UK
- Self Assessment tax returns: deadlines – GOV.UK
- Disagree with a tax decision or penalty – GOV.UK
This guide is general information, not legal, tax or financial advice. Rules and rates change, so check the linked GOV.UK pages for the current position.