Self Assessment late filing penalties start with a fixed £100 as soon as your return is one day late, even if you owe no tax. They then build through daily penalties after 3 months and further charges at 6 and 12 months, so a return that is a year late can cost £1,600 or more before any tax or interest.
The 2025/26 tax return is due by 31 October 2026 on paper or 31 January 2027 online. With those dates approaching, this guide explains exactly how the penalties are calculated, how they differ from late payment penalties, when you can appeal, and what to do if you already know you will struggle to file or pay on time.
Key takeaways
- One day late costs £100, whether or not you owe any tax.
- After 3 months, daily penalties of £10 can run for up to 90 days (£900).
- At 6 months and 12 months: 5% of the tax due or £300 each time, whichever is greater.
- Late payment penalties and interest are charged on top.
- Filing on time, even if you cannot pay, avoids the filing penalties entirely.
What a late filing penalty is
A late filing penalty is a charge HMRC makes when a Self Assessment tax return arrives after the deadline. It is separate from the tax itself, separate from interest, and separate from any penalty for paying late. The rules are set out on GOV.UK's Self Assessment penalties page, and HMRC provides a calculator to estimate your penalty for late returns and payments.
How the penalties build up
| How late | Late filing penalty | Late payment penalty |
|---|---|---|
| 1 day | £100 fixed penalty | Interest starts on unpaid tax |
| 30 days | No further charge yet | 5% of tax still unpaid |
| 3 months | £10 a day for up to 90 days (maximum £900) | No further charge yet |
| 6 months | 5% of the tax due or £300, whichever is greater | A further 5% of tax still unpaid |
| 12 months | A further 5% of the tax due or £300, whichever is greater | A further 5% of tax still unpaid |
In serious cases, for example where HMRC believes information has been deliberately withheld, the 12-month filing penalty can be much higher. Rates and amounts can change, so check the current figures on GOV.UK.
Which deadlines apply to the 2025/26 return
For the tax year that ended on 5 April 2026, a paper return is due by 31 October 2026 and an online return by 31 January 2027. Any tax owed is also due by 31 January 2027. If you miss the paper deadline you can still file online by 31 January without a penalty, which is why our guide to the paper return deadline suggests most people file online.
If HMRC sent your notice to file late in the year, you may have a different deadline shown on that notice. And if you were newly self-employed in 2025/26 and have not yet registered, do that first: see our guide to the registration deadline.
How this fits with Making Tax Digital
The penalties in this article apply to the 2025/26 return for everyone. People who joined Making Tax Digital for Income Tax on 6 April 2026 move to a different, points-based system for late submissions from the 2026/27 tax year onwards. If that is you, read our guide to MTD penalty points alongside this one, because for a period you will have obligations under both sets of rules.
Appeals and reasonable excuse
You can appeal against a penalty if you had a reasonable excuse for filing late: something that stopped you meeting the deadline despite taking reasonable care. HMRC's examples, listed on GOV.UK, include a serious or life-threatening illness, the death of a close relative shortly before the deadline, an unexpected hospital stay, and problems with HMRC's online services. You must file the return as soon as you can once the problem has passed, and you normally have 30 days from the date of the penalty notice to appeal.
HMRC does not usually accept that you forgot, that you found the online system hard to use, that you were waiting for someone else, or that you did not get a reminder. An appeal should be honest and specific; an invented excuse can lead to far more serious consequences than the penalty.
Step by step: if you are going to be late
- Do not ignore it. Penalties grow with time, so every week matters.
- Check you can log in to your HMRC online account now. Recovering a lost user ID or password can take time.
- Gather the essentials: income records, expenses, any P60 or P45, bank interest and your Unique Taxpayer Reference.
- File the return even if you cannot pay. Filing stops the filing penalties.
- Use accurate figures where you can. If a figure is genuinely not yet available, HMRC guidance explains how to use a provisional figure and correct it later.
- Arrange payment. If you cannot pay in full, look at a Time to Pay arrangement on GOV.UK's page for difficulties paying HMRC.
- Appeal promptly if you have a genuine reasonable excuse.
Worked example (illustrative example)
"Dalia", an invented illustrative example, is a self-employed translator. Her 2025/26 return is due online by 31 January 2027 and shows £2,400 of tax to pay. She does not file or pay until 10 August 2027, just over 6 months late, and has no reasonable excuse.
- Fixed late filing penalty: £100
- Daily penalties: 90 days at £10 = £900
- 6-month filing penalty: 5% of £2,400 is £120, so the £300 minimum applies
- Late payment penalty at 30 days: 5% of £2,400 = £120
- Late payment penalty at 6 months: 5% of £2,400 = £120
Dalia's penalties total £1,540, on top of the £2,400 tax and interest for the period it was unpaid. Had she filed by 31 January and set up a payment plan, the filing penalties of £1,300 would not have arisen at all. The person and figures are invented and simplified to illustrate how the charges add up.
Common mistakes
- Assuming no tax due means no penalty. The £100 applies regardless.
- Delaying the return because you cannot pay. That adds filing penalties to payment penalties.
- Leaving the online account set-up to the last week of January.
- Ignoring a notice to file because you think you no longer need a return. Tell HMRC instead and ask for it to be withdrawn.
- Missing the 30-day appeal window.
- Forgetting payments on account, which can make the January bill larger than expected.
File on time, without the scramble
Our personal tax service starts from £180 per year and covers preparing and filing your Self Assessment return ahead of the deadline. If you already have one or more returns outstanding, our catch-up plan explains how to get straight, and our guide to payments on account explains what you will need to pay in January.
Worried about a deadline or a penalty notice? Get in touch or see our pricing.
Frequently Asked Questions
How much is the penalty for a late Self Assessment tax return?
The penalty is £100 if your return is up to 3 months late. After 3 months, HMRC can charge £10 a day for up to 90 days. At 6 months and again at 12 months there are further penalties of 5% of the tax due or £300, whichever is greater. Late payment penalties and interest are charged separately.
Do I get a penalty if I owe no tax?
Yes. The £100 late filing penalty applies even if you have no tax to pay or have already paid everything you owe. The daily penalties and the £300 minimum penalties at 6 and 12 months can also apply with no tax due, so a nil return filed very late can still cost well over £1,000.
Can I appeal a Self Assessment late filing penalty?
Yes, if you have a reasonable excuse, such as a serious illness, a bereavement or a failure of HMRC's online services. You normally need to appeal within 30 days of the date on the penalty notice. Simply forgetting, finding the system difficult or relying on someone else who let you down is not usually accepted.
What is the difference between late filing and late payment penalties?
Late filing penalties are for sending the return after the deadline. Late payment penalties are for paying the tax after the deadline, and are 5% of the tax unpaid at 30 days, 6 months and 12 months. They are separate, so someone who both files and pays late can be charged both, plus interest.
What should I do if I cannot pay my tax bill on time?
File the return on time anyway, because that avoids the late filing penalties. Then contact HMRC before the payment deadline or set up a Time to Pay arrangement online if you are eligible. An agreed payment plan can prevent late payment penalties, although interest still runs. Check the current eligibility conditions on GOV.UK.
Related reading
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Last reviewed: 1 October 2026.
This article is general information, not personal tax advice. Speak to a qualified accountant about your own circumstances before acting on it.