Late Self Assessment: Penalties and How to Fix It
Missing a Self Assessment deadline is stressful, but it is fixable, and the sooner you act the less it costs. HMRC charges separate penalties for filing late and paying late, and both grow over time. This guide explains how the penalties work, what to do first, when you can appeal and how to make sure it does not happen again. It is general information, not tax advice; penalty rules can change, so check GOV.UK or speak to an accountant about your case.
Key takeaways
- There are two kinds of penalty: one for filing late and one for paying late. You can get both.
- A late return brings a £100 penalty immediately, even if you owe no tax, and more after 3, 6 and 12 months.
- Late payment brings penalties of 5% of unpaid tax at 30 days, 6 months and 12 months, plus interest.
- File as soon as you can and pay what you can: both stop further penalties building up.
- If you had a reasonable excuse, you can appeal.
Every year, plenty of freelancers and sole traders miss the Self Assessment deadline. Sometimes it is a busy January, sometimes missing paperwork, sometimes illness or a family emergency. Whatever the reason, the worst thing you can do is ignore it. Penalties keep adding up while the return stays unfiled, and interest keeps running on unpaid tax.
This guide covers the standard Self Assessment penalty rules. If you are within Making Tax Digital for Income Tax, a points-based system applies to late submissions instead; see our guide to Making Tax Digital for Income Tax for that.
The deadlines you might have missed
Self Assessment deadlines relate to the tax year that ended on the previous 5 April.
| What | Deadline |
|---|---|
| Paper tax return | 31 October after the end of the tax year |
| Online tax return | 31 January after the end of the tax year |
| Balancing payment for the year | 31 January |
| First payment on account | 31 January |
| Second payment on account | 31 July |
| Registering for Self Assessment (new sole traders) | 5 October after the end of the tax year you started |
For example, for the tax year 6 April 2025 to 5 April 2026, the online return and balancing payment are due by 31 January 2027.
Late filing penalties
Filing penalties apply if your return reaches HMRC after the deadline. They apply even if you owe no tax, or if you have already paid.
| How late the return is | Penalty |
|---|---|
| 1 day late | £100 |
| 3 months late | £10 a day, up to a maximum of £900 |
| 6 months late | 5% of the tax due or £300, whichever is greater |
| 12 months late | Another 5% of the tax due or £300, whichever is greater |
Example
Imagine a freelancer files her online return seven months after the 31 January deadline, and the tax due on it was £2,000 (a made-up figure). She would face the £100 initial penalty, £900 in daily penalties after three months (the maximum) and, at six months, the greater of 5% of £2,000 or £300, which is £300. That is £1,300 in filing penalties alone, before any late payment penalties or interest. Filing even a few weeks earlier would have avoided most of it.
Late payment penalties and interest
Payment penalties are separate. They apply to tax you have not paid by the deadline.
- 30 days late: 5% of the tax unpaid at that date.
- 6 months late: a further 5% of the tax unpaid at that date.
- 12 months late: a further 5% of the tax unpaid at that date.
- Interest: charged on unpaid tax and on unpaid penalties from the date they were due until you pay.
Because the percentages apply to what is still unpaid at each point, paying part of the bill early reduces later penalties even if you cannot pay it all.
Common mistake
Waiting to file until you can afford to pay. Filing and paying are separate. Filing late adds filing penalties on top of payment penalties, so file on time, or as soon as possible, even if you cannot pay the full amount yet, and then talk to HMRC about paying.
What to do right now
If you have missed a deadline, work through these steps in order.
- Check you actually needed to file. If HMRC asked you to file, you generally must, even if your income was low. If you think you should not have been in Self Assessment, contact HMRC, as you may be able to ask them to withdraw the requirement to file.
- Gather your records quickly. Use bank statements, invoices and receipts. If some figures are missing, make careful estimates and note them, and correct the return later when you have the details.
- File the return online. You can file after the deadline in the same way as before it. Filing stops the daily penalties and the later filing penalties from growing.
- Pay what you can. Every pound paid reduces interest and future late payment penalties.
- Talk to HMRC if you cannot pay. You may be able to set up a payment plan to spread the cost. Contact them before more penalties are added.
- Consider an appeal. If you had a reasonable excuse, appeal the penalties, following the instructions on the penalty notice.
Pro tip
If you missed the registration deadline as a new sole trader, register as soon as you realize. Registering late and not paying by 31 January can lead to a "failure to notify" penalty, and acting early generally puts you in a better position than waiting for HMRC to find you.
Appealing with a reasonable excuse
HMRC can cancel penalties if you had a reasonable excuse for missing the deadline. That means something outside your control that stopped you filing or paying on time, and you then put things right without unreasonable delay once the problem ended.
Situations that may count include:
- Serious illness or a stay in hospital
- The death of a partner or close relative shortly before the deadline
- Unexpected failure of HMRC's online service or your computer at the critical time
- A fire, flood or theft that prevented you from completing the return
- Postal delays you could not have predicted
Things that usually do not count include being too busy, finding the return too difficult, relying on someone else who let you down, or not receiving a reminder. Every case is judged on its own facts, so if you are unsure, explain your situation honestly and let HMRC decide.
How to appeal
Your penalty notice explains how to appeal and the deadline for doing it. You can usually appeal online or by post. Include the dates, what happened, any evidence such as hospital letters, and when you filed and paid once the problem ended. File the return first: an appeal is much weaker if the return is still outstanding. If HMRC rejects your appeal, you can ask for a review or take it to the tax tribunal.
Stop it happening again
Most missed deadlines are not about money but about leaving everything until January. A few habits change that.
- File early. The return can be filed from 6 April, straight after the tax year ends. Filing in spring or summer gives you months of warning about what you owe.
- Keep books up to date. A short weekly bookkeeping routine means your figures are ready when you need them.
- Save for tax as you go. Move a percentage of every payment into a separate tax account.
- Put every deadline in your calendar. Include 31 July for the second payment on account, which is easy to forget.
- Get help early. If your affairs are complicated, book an accountant well before January.
It also helps to understand payments on account before they arrive. Once they apply, your 31 January bill can include both the balance for the previous year and the first advance payment for the current year, which can be a much larger sum than you expect. Knowing this months in advance gives you time to save, or to apply to reduce your payments on account if you genuinely expect lower profits. Finally, check your HMRC online account a few times a year. It shows what HMRC thinks you owe and when, so you can spot a missed payment or an unexpected charge long before it turns into a penalty.
Missed deadline action plan
- Confirm which return or payment you missed and for which tax year
- Collect bank statements, invoices and receipts for that year
- File the return online as soon as possible
- Pay as much of the bill as you can now
- Contact HMRC about a payment plan if you cannot pay in full
- Appeal any penalties if you had a reasonable excuse
- Add next year's deadlines to your calendar today
Frequently asked questions
Do I get a penalty if I owe no tax?
Yes, the £100 initial late filing penalty and the later filing penalties can still apply even if there is no tax to pay. If you believe you should not have been asked to file, contact HMRC promptly.
Is there a grace period after 31 January?
You should not rely on one. Officially, the return is late from 1 February. Treat 31 January as a hard deadline and aim to file well before it.
Will a late return trigger an investigation?
A late return on its own does not mean an investigation, but it does put you on HMRC's radar for penalties and reminders. Filing accurately and promptly, with good records behind your figures, is the best protection.
Can I amend a return I rushed to file late?
Generally yes. You can usually correct a return through your HMRC online account within a set period after the deadline. If you used estimates, update them as soon as you have the real figures.
Related reading
The bottom line
If you have missed a Self Assessment deadline, file as soon as possible, pay what you can and contact HMRC if you need time. Penalties grow over time, so every week counts. If something outside your control caused the delay, appeal with a clear explanation and evidence.
This is general information, not tax advice. Penalty rules and deadlines can change, so check the latest guidance on GOV.UK or HMRC, or ask an accountant to help you deal with your situation.
