A Self Assessment return filed online one day after 31 January costs £100, even if you owe nothing. Leave it for three months and daily penalties of £10 start, up to £900. At six and 12 months, each adds the greater of 5% of the tax due or £300. Paying the tax late is penalised separately, at 5% of the unpaid tax at 30 days, six months and 12 months, with interest on top.
The two sets of penalties run independently. Filing the return stops the filing penalties building, even if you cannot yet pay. This guide sets out the deadlines, what each penalty costs, two worked examples, how appeals work and what HMRC's payment plans offer.
Self Assessment deadlines at a glance
| What | When | Notes |
|---|---|---|
| Register for Self Assessment | 5 October | After this date, a 'failure to notify' penalty is possible if you do not pay all your tax by 31 January |
| Paper return | 31 October | For the 2024/25 year this was 31 October 2025 |
| Online return | 31 January | For the 2024/25 year this was 31 January 2026 |
| Pay the tax | 31 January | Interest runs from the day after the deadline |
| Second payment | 31 July | Sometimes due; see payments on account below |
The paper deadline is three months earlier than the online one, and that matters. LITRG, the Low Incomes Tax Reform Group, points out that a paper return filed late may already be attracting daily penalties when an online one would not, so paper filers who are late are likely to pay more.
Registering by 5 October
If you register after 5 October and do not pay all of your tax bill by 31 January, GOV.UK says you may get a 'failure to notify' penalty. It is based on the amount still left to pay, and you receive it within 12 months after HMRC receives your return. The rate is not set out in the guidance we have relied on, so check the HMRC page on 'failure to notify' penalties if it applies to you.
Payments on account
Self Assessment payments usually fall due on 31 January each year, and sometimes also on 31 July. The 31 July payment is a payment on account, an advance towards the following year's bill. How the amounts are calculated, and whether you have to make them, is covered in our guide to payments on account. Check your own HMRC account for the amounts and dates that apply to you.
Late filing penalties
HMRC's guidance on Self Assessment penalties lists four stages:
- Initial penalty: £100. It arises the day after the filing date.
- After three months: additional daily penalties of £10 a day, up to a maximum of £900. That is 90 days at £10.
- After six months: a further penalty of 5% of the tax due or £300, whichever is greater.
- After 12 months: another 5% or £300 charge, whichever is greater.
Some points the headline figures hide:
- You owe nothing and still get the penalty. LITRG notes that HMRC still charges late filing penalties if you owe no tax, and even if your return shows a repayment due to you.
- The later penalties do not depend on the earlier ones. HMRC's manual says a person becomes liable to the six-month penalty even if they have not been charged daily penalties.
- Partnerships. All partners are charged a penalty if a partnership return is late.
- Deliberate withholding can cost far more. The 12-month penalty can rise to 70% of the tax liability where a person deliberately withholds information that would help HMRC assess the correct tax, and to 100% if the withholding is concealed. HMRC's manual describes this as the only late filing penalty that looks at behaviour.
The dates for a 2024/25 online return
For a 2024/25 online return due on 31 January 2026, LITRG gives these dates: the £100 penalty applied from 1 February 2026, daily penalties normally started from 1 May 2026, and the six-month and 12-month penalties fell on 31 July 2026 and 31 January 2027 in most cases.
If you are in this position now, file today. Each day removed from the timeline is money saved, and once HMRC receives an online return the daily penalties stop.
Late payment penalties and interest
Paying late is a separate matter from filing late. HMRC's guidance says you get penalties of 5% of the tax unpaid at:
- 30 days
- six months
- 12 months
You are also charged interest on the amount owed. LITRG explains that interest starts from the day after the payment deadline, whereas the late payment penalties usually apply once tax is more than 30 days late.
On the rate, Which? reported in February 2026 that interest on unpaid balances stood at 7.75%, which it described as the Bank of England base rate plus 4%. Because the rate follows the base rate, check the current figure before you calculate anything. Interest is also charged on unpaid penalties: a late filing penalty must be paid within 30 days of the notice, and interest runs from the end of that period.
Two worked examples
The first is HMRC's own, from its internal manual. The second applies the same rules to a larger bill.
Example 1: a low liability, more than 12 months late
Jonathan's 2012-13 online return was due on 31 January 2014. He filed it on 3 February 2015, showing a liability of £3,000. HMRC's manual works out his late filing penalties as:
| Date | Penalty |
|---|---|
| 1 February 2014 | £100 initial penalty |
| 1 May to 29 July 2014 | £900 daily penalties (90 days at £10) |
| 1 August 2014 | £300 (greater than 5% of £3,000) |
| 1 February 2015 | £300 (greater than 5% of £3,000) |
That adds up to £1,600 for a return that showed £3,000 of tax. At this level the £300 minimum bites, because 5% of £3,000 is only £150.
The manual's paper example, Ben, follows the same pattern, but each date arrives three months earlier because the paper deadline is 31 October.
Example 2: a larger bill, filed and paid very late
This one is our own illustration of the stated rules. Suppose a return shows £8,000 of tax. It is filed 14 months late, and the £8,000 is still unpaid throughout.
Late filing:
- £100 initial penalty
- £900 daily penalties
- six months: 5% of £8,000 is £400, which beats £300, so £400
- 12 months: £400 again
Filing penalties come to £1,800.
Late payment: 5% of £8,000 is £400 at each of 30 days, six months and 12 months, so £1,200.
The penalties alone total £3,000 on an £8,000 bill, before interest. At the 7.75% rate Which? reported in February 2026, a year of interest on £8,000 would be about £620. The rate will have moved since, so use that only as a sense of scale.
Reasonable excuse and appeals
A penalty can be cancelled if you have a reasonable excuse. HMRC's manual sets out three limits on what counts:
- Not having enough money is not a reasonable excuse, unless it is down to events outside your control.
- Relying on someone else is not a reasonable excuse, unless you took reasonable care to avoid the failure.
- If a genuine excuse ends, you are treated as still having it, provided you fix the failure without unreasonable delay once it ends.
Which? lists the kinds of situation that can qualify: a close bereavement shortly before the deadline, serious illness or an unexpected hospital stay, a mental health condition that affected your ability to comply, HMRC's online services failing, your computer or software failing while you prepared the return, a PIN, User ID or password applied for in good time but arriving too late, records destroyed by theft, fire or flood, and unforeseen postal disruption where you posted in good time. LITRG gives prolonged ill-health or bereavement as examples.
Separately, HMRC can give a special reduction to a late filing penalty where special circumstances apply. HMRC's manual is explicit that ability to pay is not a special circumstance.
How to appeal
- File the return first. Which? reports that HMRC will not consider an appeal until the outstanding return has been submitted.
- Gather evidence. Hospital letters, death certificates, screenshots of error messages. HMRC decides largely on what you can show.
- Appeal within 30 days of the date on the penalty notice. LITRG says HMRC may in some cases consider a late appeal.
- Use HMRC's route. HMRC's appeal guidance lets you appeal online or download form SA370 or SA371 to appeal by post. You need the penalty date, the date you filed, the date you paid if you have, and details of your excuse.
If you disagree with the outcome, you can ask HMRC to review the decision. On a late filing penalty, the First-tier Tribunal can then confirm or cancel HMRC's decision, or substitute another that HMRC had power to make.
Should you pay while you appeal? HMRC says you should consider it. If you do not pay and the appeal is rejected, you pay interest on the penalty from the date it was due. If the appeal succeeds, HMRC repays what you paid with interest from the date you paid it, provided you have no other tax outstanding. HMRC's manual adds that there is no obligation to pay a late filing penalty before the appeal is decided, so this is your choice.
Appeals are not a long shot. Which? reports HMRC data showing 32,258 appeals against late filing and late payment penalties between 31 March and 30 September 2025, of which taxpayers won 20,076.
If you did not need to file at all
Check whether you met HMRC's Self Assessment criteria for the year. If you did not, you can ask HMRC to cancel the notice to file, and any late filing penalties are cancelled with it. LITRG gives 5 April 2027 as the deadline for asking to cancel a 2024/25 return. Directors in particular are often unsure whether they need to file; see our guide on whether company directors need to file Self Assessment.
If you cannot pay: Time to Pay
HMRC's guidance on difficulty paying says that if you cannot pay your tax bill in full, you may be able to set up a payment plan to pay in instalments. HMRC checks that the plan is affordable. If you cannot agree one, it asks you to pay in full.
What to expect:
- File the return first. LITRG says HMRC will only discuss a time to pay arrangement after you have filed.
- You need details to hand: your Unique Taxpayer Reference, UK bank details you are authorised to set up a Direct Debit on, and details of your income and spending.
- Online or by contact. HMRC runs an online service that checks whether you are eligible. Which? reports that online set-up applies where the bill is under £30,000, you act within 60 days of the 31 January deadline and have no other HMRC debts. Otherwise you contact HMRC.
- Expect to use savings. HMRC expects you to use savings or assets to reduce the debt as much as possible.
- Monthly amount. You are usually asked to pay around half of what you have left each month after rent, food, utilities and fixed outgoings.
- No fixed term. There is no time limit on how long a plan lasts. It depends on what you owe and can afford.
- Interest continues. Which? notes interest is still charged on the outstanding bill. Paying faster means paying less in total.
- Penalties stop if you keep to the plan. LITRG says no further late payment penalties are charged once an arrangement is in place, provided you keep to its terms.
If you miss a payment under the plan, HMRC contacts you to find out why and tries to rearrange it. If you do not get in touch or cannot agree a plan, HMRC can ask a debt collection agency to collect, collect from your wages or pension, take and sell goods or take money from your bank account (England, Wales and Northern Ireland), go to court or make you bankrupt. HMRC says it tells you before taking any of these steps. You cannot appeal HMRC's decision on a payment plan, but you can make a complaint about how you were treated.
If your bill is not yet overdue, HMRC mentions a Budget Payment Plan, which lets you pay weekly or monthly towards your next Self Assessment bill.
What to do now
- Overdue return: file it online today, even if you cannot pay. Do not wait for the full information if estimates will do; LITRG says provisional or estimated figures can be used and the actual figures sent when available.
- Cannot pay: file, then contact HMRC about a payment plan before the 30-day and six-month penalty points arrive.
- Penalty you think is wrong: appeal within 30 days with evidence, and decide whether to pay it while the appeal runs.
- Not sure you should be in Self Assessment: ask HMRC to cancel the notice to file before you spend time on the return.
Deplexify prepares accounts and tax filings for small organisations in the UK; our UK page shows what we cover.
Frequently Asked Questions
What is the penalty for filing a Self Assessment return one day late?
£100. HMRC charges it automatically from the day after the filing date, and it applies even if you owe no tax or are due a refund.
How much can daily penalties reach?
Daily penalties are £10 a day and start after three months. They stop at a maximum of £900.
Do I pay a penalty if I file on time but pay late?
Yes. Late payment penalties are 5% of the unpaid tax at 30 days, six months and 12 months, plus interest from the day after the payment deadline.
Can I appeal a penalty?
Yes, if you have a reasonable excuse or believe the penalty is wrong. File the return first, then appeal within 30 days of the penalty notice, online or by form SA370 or SA371.
Will HMRC set up a payment plan if I cannot pay on 31 January?
HMRC may agree one if it is affordable for you. It will usually expect around half of your monthly surplus, and interest still runs. Keeping to the plan stops further late payment penalties.