Self Assessment late filing penalty: amounts, appeal and instalments

In short

• Self Assessment late filing penalty: £100 to start with for a late return, and after 3 months £10 for each day (up to £900). For late payment, 5% of the tax unpaid at 30 days, at 6 months and at 12 months. Standard deadline for the 2025/26 online return: 31 January 2027 (GOV.UK, as of November 2026).
• Interest: from 24 November 2026 late payment interest is 8.00% a year (GOV.UK, as of November 2026).
• Appeal: you usually have 30 days from the date the penalty was issued. You can appeal online or on form SA370 or SA371 if you have a reasonable excuse or the penalty is wrong (GOV.UK, as of November 2026).
• Instalments: if you cannot pay your whole tax bill, you can ask for a payment plan in monthly instalments. HMRC's phone line for overdue Self Assessment payments: 0300 200 3820 (GOV.UK, as of November 2026).
• Send your return or payment as soon as you can: this helps you avoid further penalties.

How much is the penalty for a late Self Assessment return

You get a penalty if you need to complete a Self Assessment tax return and you file it late or pay your tax late (GOV.UK, as of November 2026). The standard deadline for the 2025/26 online return is 11:59pm on 31 January 2027. If you registered after 5 October 2026, HMRC will send a letter or email giving you a different filing deadline: three months from the date of that letter or email. You must still pay the tax by 11:59pm on 31 January 2027. A paper return had to reach HMRC by 11:59pm on 31 October 2026. The deadline for earlier tax years has already passed: send your return or payment as soon as possible to avoid further penalties (GOV.UK).

Late tax return:

Late payment of tax:

• HMRC sends a penalty notice when you miss the deadline for filing or paying. You must pay a penalty within 30 days of the date on the penalty notice.
• If a partnership tax return is late, all partners are charged a penalty.
• If you register after 5 October and do not pay all of your tax bill by 31 January, you may get a "failure to notify" penalty.

We explain how to file your return in our guide to Self Assessment step by step, and give a general overview of UK taxes in our guide to income tax in the UK.

Interest on unpaid tax

HMRC charges interest on the amount you owe (GOV.UK). Late payment interest is the Bank of England base rate plus 4 percentage points. On 5 November 2026 the Bank of England raised the base rate from 3.75% to 4.00%, so from 24 November 2026 late payment interest is 8.00% a year (as of November 2026; HMRC announcement, table of rates). The rate changes with Bank of England decisions, so check the current rate in the table.

How to appeal a late filing or late payment penalty

1. Find the date the penalty was issued on the penalty notice. You usually have 30 days from that date to appeal (as of November 2026, GOV.UK). If you have missed the deadline, you will need to give a reason.
2. Gather your details (GOV.UK): the date the penalty was issued, the date you filed your return (if it has been filed), the date you paid your tax (if it has been paid) and details of your reasonable excuse for the delay.
3. Appeal. Explain why the penalty should not apply, for example because of a reasonable excuse or because the penalty is wrong. You can appeal online, or download form SA370 or SA371 and send it by post. If you do not have a form, send a signed letter to the HMRC office that deals with your return (GOV.UK): explain, with dates, why your return or payment was late, and give your reference number, for example your UTR. If you had computer problems, add the date you tried to file or pay online and details of any system error message.
4. Decide about paying. According to GOV.UK, once you have appealed against a penalty you do not have to pay until your appeal has been settled, but you can be charged interest on the tax in dispute. HMRC also says you should consider paying the penalty: if you do not and your appeal is rejected, you will have to pay interest on the penalty from the date it was due. If HMRC agrees your appeal, it will repay what you paid with interest from the date you paid it (if you do not have any other outstanding tax to pay).

The outcome of an appeal depends on the circumstances, and nobody can promise it will succeed. If you are not sure what to do, use free advice (see "Where to get help").

Reasonable excuse: what HMRC may and may not accept

A reasonable excuse is something that stopped you meeting a tax obligation for a valid reason (GOV.UK, as of November 2026). You will usually need to provide one when challenging some penalties or if you miss a deadline, for example for an appeal. If you think the penalty is wrong, explain why to HMRC. Send your return or payment as soon as you are able to.

May count, for example:

• your partner or another close relative died shortly before the deadline,
• an unexpected stay in hospital, or a serious or life-threatening illness,
• your computer or software failed while you were preparing your online return, or there were issues with HMRC online services,
• a fire, flood or theft prevented you from completing your return,
• postal delays that you could not have predicted,
• delays related to a disability or mental illness you have,
• you were unaware of or misunderstood your legal obligation,
• you relied on someone else to send your return, and they did not.

Will not count if:

• your cheque bounced or your payment failed because you did not have enough money,
• you found the HMRC online system too difficult to use,
• you did not get a reminder from HMRC,
• you made a mistake on your return.

The GOV.UK list says what may count, so it is not a guarantee of the outcome.

Review and the tax tribunal: what happens if HMRC says no

If HMRC does not change its decision or you cannot reach an agreement, it will offer you a review (GOV.UK, as of November 2026). You can also request one at any time after you appeal, without waiting for the result: write to the same HMRC office. A review is carried out by an officer from a different team and usually takes 45 days. If the review upholds or varies the decision and you agree with the outcome, you pay what you owe. If you disagree, you can appeal to the tax tribunal, usually within 30 days of the date on the review result letter (if you have requested a review, you wait for its outcome first).

The tribunal is independent of the government and HMRC, and listens to both sides (GOV.UK). You can appeal online or by post, using form T240. If you miss the deadline, explain why, and a judge will decide whether to accept your appeal. If you are appealing a penalty, you do not have to pay it upfront.

If you cannot pay your tax: a payment plan in instalments

If you cannot pay your tax bill in full, you may be able to set up a payment plan in monthly instalments (GOV.UK, as of November 2026). HMRC checks whether the plan is affordable for you; if you cannot agree one, it will ask you to pay in full. Have ready (GOV.UK): the reference number for the tax (for example your UTR from HMRC letters), UK bank account details from which you can set up a Direct Debit, and details of your income and spending.

1. Use the HMRC online service to check if you are eligible, and set up the plan.
2. If you cannot do it online, contact HMRC. It will ask, among other things, how much you can repay each month, and expects you to use savings or assets to reduce your debt.
3. As evidence of your income and spending, HMRC accepts a Standard Financial Statement from independent debt advice (for example from Citizens Advice).

Instalment size and length. The amount is based on what you have left after rent, food, utility bills and fixed outgoings; HMRC will usually ask for around half of that. You can pay more: paying quicker means less interest. There is no time limit on how long a plan can last. If your circumstances change, contact HMRC, because the plan can be made longer or shorter. If you miss a payment, HMRC will contact you and, where possible, try to rearrange the plan.

The £30,000 limit. According to an HMRC announcement of 9 December 2025 (GOV.UK), a Time to Pay arrangement for bills of up to £30,000 can be set up without contacting HMRC, but only once your return has been filed. Above that amount, or if a longer repayment period is needed, you need to contact HMRC. These are conditions from a press release, so check the current ones in the HMRC service.

Phone. The "Payment problems: enquiries" page gives 0300 200 3820 for overdue Self Assessment payments, Monday to Friday, 8am to 6pm, closed on bank holidays (GOV.UK).

If you do not contact HMRC. HMRC may, among other things, ask a debt collection agency to collect the money, collect it from your wages or pension, take you to court or make you bankrupt; it will tell you before taking such steps. You cannot appeal against HMRC's decision on a payment plan, but you can make a complaint about how you were treated. For larger debts, see our guide to a debt relief order, an IVA and bankruptcy.

New penalties from April 2027

From April 2027 the new penalties will apply to everyone who submits a personal Self Assessment tax return (GOV.UK, as of November 2026). They do not apply to the 2025/26 return with its deadline of 31 January 2027: the current penalties still apply to previous tax years. The new late submission penalties are points based; under Making Tax Digital for Income Tax the threshold is 4 points, and once you reach it the penalty is £200, with the same amount for each further missed deadline. The new system also changes late payment penalties; check the HMRC guidance for details. There are no changes to how late payment interest works. Before the deadline, check on GOV.UK how the new rules apply in your case.

Scotland, Wales and Northern Ireland

The GOV.UK pages we use do not give differences between the parts of the UK in penalties, appeals or payment plans. Debt recovery and advice organisations differ (GOV.UK, as of November 2026):

• Debt recovery: HMRC lists taking things you own and selling them, and taking money from your bank account or savings, for people who live in England, Wales or Northern Ireland.
• Free debt advice: in England and Wales MoneyHelper, in Scotland Scotland Debt Solutions, in Northern Ireland Advice NI.

Frequently asked questions

Can I check the amount of a penalty before I appeal?

Yes. HMRC has a calculator that estimates penalties and interest for people who have missed Self Assessment deadlines. It is an estimate, not an HMRC decision.

I got a penalty but did not need to file a return. What should I do?

If you do not need to send a Self Assessment tax return, you can ask HMRC to cancel the penalty. If you no longer need to send one, you should tell HMRC early enough, or you may get a penalty. You can check how to do this in the GOV.UK appeal guidance.

Can I appeal against HMRC's decision on a payment plan?

No, but you can make a complaint if you are unhappy about how you were treated. If no plan is agreed, HMRC will ask you to pay the full amount.

Where to get help

• HMRC, Payment problems: enquiries, Self Assessment payment: 0300 200 3820, Monday to Friday 8am to 6pm, closed bank holidays (as of November 2026). Contact page. If you are having problems paying, you can also ask HMRC's digital assistant.
• Tax tribunal: Appeal to the tax tribunal.
• Free debt advice: Citizens Advice; in England and Wales MoneyHelper, in Scotland Scotland Debt Solutions, in Northern Ireland Advice NI.
• Not sure a message about a penalty is genuine: our guide to scams in the UK explains how to spot a scam and where to report it.