The short answer
The Self Assessment late filing penalty is £100 as soon as your return is late, even if you owe no tax. After 3 months it grows by £10 a day up to £900, then 5% of the tax due or £300 at 6 and 12 months. Late payment adds 5% charges plus interest. You can appeal with a reasonable excuse.
- Return 1 day late
- £100
- Return 3 months late
- £10 a day, up to £900
- Tax 30 days late
- 5% of unpaid tax
- Appeal window
- Generally 30 days from the notice
How much is the Self Assessment late filing penalty?
If your return reaches HMRC after the deadline, you get a £100 penalty straight away. For the 2025/26 tax year the deadline is 31 January 2027 for online returns and 31 October 2026 for paper returns. The £100 applies even if you owe no tax, or HMRC owes you a refund.
The longer the return stays outstanding, the more the penalties grow:
| How late the return is | Penalty | Running total (if 5% is under £300) |
|---|---|---|
| 1 day late | £100 | £100 |
| 3 months late | £10 a day for up to 90 days, maximum £900 | Up to £1,000 |
| 6 months late | 5% of the tax due or £300, whichever is greater | Up to £1,300 |
| 12 months late | Another 5% of the tax due or £300, whichever is greater | Up to £1,600 |
Where a large amount of tax is due, the 5% charges can be much more than £300. In serious cases, such as deliberately withholding information, HMRC can charge more at 12 months.
What are the penalties for paying Self Assessment tax late?
Filing and paying are treated separately. You can file on time and still get penalties for paying late, or the other way round. Tax for 2025/26 is due by 31 January 2027.
| How late the payment is | Penalty |
|---|---|
| 30 days late | 5% of the tax unpaid at that date |
| 6 months late | Another 5% of the tax unpaid at that date |
| 12 months late | Another 5% of the tax unpaid at that date |
Interest is charged on top. It runs on late tax from the day it was due until the day it is paid, and also on unpaid penalties. HMRC sets the rate, which is linked to the Bank of England base rate, so it changes from time to time. Interest is not a penalty, so you cannot appeal against it on the grounds of a reasonable excuse.
How do late filing and late payment penalties add up?
Because the two types of penalty run side by side, a missed deadline can cost far more than the first £100. Here is a simple, hypothetical example.
In this example the penalties add up to over 40% of the tax itself. Filing on time, even if you cannot pay in full, stops the filing penalties from building up.
What counts as a reasonable excuse for HMRC?
A reasonable excuse is something that stopped you meeting the deadline even though you took reasonable care. HMRC looks at your circumstances, and you also need to have put things right without unreasonable delay once the problem ended. Every case is judged on its own facts, so these are general examples, not guarantees.
| HMRC may accept | HMRC usually does not accept |
|---|---|
| Your partner or a close relative died shortly before the deadline | You relied on someone else to file and they did not |
| An unexpected stay in hospital stopped you dealing with your affairs | You did not have the money to pay the tax |
| A serious or life-threatening illness | You found the HMRC online system too difficult |
| Your computer or software failed while you were preparing the return | You did not receive a reminder from HMRC |
| Service problems with HMRC online services | You made a mistake on your return |
| A fire, flood, theft or postal delays you could not have predicted | You were too busy |
Keep evidence wherever you can: a hospital letter, a death certificate date, a screenshot of an error message, or a repair invoice. A clear timeline of what happened and when you acted is much stronger than a general explanation.
How do I appeal an HMRC penalty?
If you think a penalty is wrong, or you had a reasonable excuse, you can appeal. You should generally appeal within 30 days of the date on the penalty notice.
- 1
File the late return first
HMRC will usually want the return filed before it looks at an appeal against a late filing penalty. Penalties keep growing until it is filed.
- 2
Check the penalty notice
Note the date of the notice, the tax year, and which penalties it covers. Check the dates and amounts are right.
- 3
Write down your reasonable excuse
Say what happened, the dates it started and ended, and when you filed or paid once the problem was over. Gather supporting evidence.
- 4
Send the appeal
You can appeal online through your HMRC account or by post using the Self Assessment penalty appeal form. Follow the guidance at GOV.UK: appeal a penalty.
- 5
Wait for HMRC’s decision
If HMRC agrees, the penalty is cancelled or reduced. If it refuses, the letter explains your options, including asking for a review by a different HMRC officer or appealing to the independent tax tribunal.
Our late tax returns and penalty appeals service can file overdue returns and prepare appeals for you.
What if I cannot pay my tax bill in full?
Do not let a payment problem stop you filing. File on time so that the filing penalties do not start, and then deal with the payment.
HMRC can agree a Time to Pay arrangement, which lets you pay what you owe in instalments. For some Self Assessment debts you can set up a payment plan online; for others you need to contact HMRC. You will usually need to show what you can afford. Interest still runs on the unpaid tax, but a plan you keep to is far better than ignoring the debt. Contact HMRC as early as you can, ideally before the deadline.
How are Making Tax Digital penalty points different?
Making Tax Digital for Income Tax (MTD) started on 6 April 2026 for sole traders and landlords with qualifying income over £50,000. People in MTD send quarterly updates through software, as well as a tax return at the end of the year.
Late quarterly updates work on a points system rather than an automatic fine. Points are not applied for 2026/27. From the following year, each missed update earns a point, and once you reach 4 points you get a £200 penalty. Your final tax return is still due by 31 January after the tax year. Read more in our Making Tax Digital for Income Tax guide.
What should I do next?
- If a return is overdue, file it now. Every month counts.
- Pay what you can, and talk to HMRC about the rest.
- If you had a genuine reason, appeal within 30 days of the penalty notice.
- Check the next dates in our Self Assessment deadline guide so it does not happen again.
If you are behind and would like help catching up, contact us for a free 20-minute chat. We will look at what is outstanding and give you a fixed price in writing within one working day.
Common questions
Do I get a late filing penalty if I owe no tax?
Yes. The £100 penalty applies when the return is late, even if there is no tax to pay. If HMRC has asked you to file but you think you did not need to, contact HMRC as it may be able to withdraw the notice and cancel the penalty.
How long do I have to appeal an HMRC penalty?
Generally 30 days from the date on the penalty notice. HMRC may accept a later appeal if you had a good reason for the delay, but it is best not to rely on that.
Can I appeal against interest?
No. Interest is not a penalty. It is charged because the tax was paid late, so a reasonable excuse does not remove it. If a penalty is cancelled, the interest on that penalty goes too.
Is not receiving a reminder a reasonable excuse?
Usually not. HMRC expects you to know your deadlines. The same goes for relying on someone else who then failed to file for you.
Does an appeal stop me paying the penalty?
If you appeal within the time limit, you do not have to pay the penalty while the appeal is considered. You should still pay the tax itself, as interest continues to run on it.
Reviewed by
Chartered Accountant, ICAEW member, at NY Accountants in Liverpool. Figures are for the 2026/27 tax year in England, Wales and Northern Ireland unless stated.
Sources
- GOV.UK: Self Assessment tax returns, penalties
- GOV.UK: Disagree with a tax decision or penalty
- GOV.UK: Reasonable excuses
This guide is general information, not advice for your situation. Talk to us before acting on it.
