How to Appeal an HMRC Penalty

Self Assessment Penalties

If your tax return is late, the first penalty is £100. After 3 months, HMRC can charge £10 a day, up to £900. After 6 months, you pay a further 5% of the tax due or £300, whichever is more, and the same again after 12 months.

If you pay late, you pay 5% of the tax unpaid at 30 days, at 6 months and at 12 months. HMRC also charges interest on the amount you owe.

For the 2025 to 2026 tax year, paper returns are due by 31 October 2026. Online returns, and the tax you owe, are due by 31 January 2027.

Your Right to Appeal

The law gives you the right to appeal against a decision that a penalty is payable, and against the amount. Your appeal must be in writing, within 30 days, and must say why you are appealing.

GOV.UK says you usually have 30 days from the date your penalty was issued. Form SA370 says within 30 days of the date shown on the front of your penalty notice.

You can appeal if you had a reasonable excuse, or if you think the penalty is wrong.

How to Appeal

GOV.UK offers an online appeal and form SA370 by post. The law says your appeal must be in writing and give your reasons, so a letter works too.

Explain why your return or payment was late, with dates. Include your name, your Unique Taxpayer Reference (UTR), the date the penalty was issued, and the date you sent your return or paid, if you have. If computer problems stopped you, give the date you tried to file or pay online and details of any error message.

If you have not sent your return or paid yet, form SA370 says to do it now to avoid further penalties.

Reasonable Excuses

GOV.UK says a reasonable excuse is something that stopped you meeting a tax obligation for a valid reason.

HMRC's examples include your partner or another close relative dying shortly before the deadline, an unexpected stay in hospital, a serious or life-threatening illness, your computer or software failing while you prepared your online return, problems with HMRC's online services, a fire, flood or theft, postal delays you could not have predicted, and delays related to a disability or mental illness.

If you relied on someone else, such as an accountant, to send your return and they did not, the law only accepts this if you took reasonable care.

HMRC will not accept that you did not have enough money, that you found the online system too hard, that you did not get a reminder, or that you made a mistake on your return. The law says a lack of money is not a reasonable excuse unless it was caused by events outside your control.

Once the problem ends, you must send your return or payment as soon as you are able to.

If You Are Late Appealing

GOV.UK says that if you miss the 30 days, you need to give a reason.

The law says HMRC must accept a late appeal if you ask in writing, you had a reasonable excuse for not appealing in time, and you asked without unreasonable delay after that excuse ended. If HMRC says no, you can ask the tax tribunal for permission.

What Happens Next

If HMRC does not change its decision, it offers you a review by someone in a different team who was not involved in the original decision. You can also ask for a review at any time after you appeal, by writing to the same HMRC office. Reviews usually take 45 days.

If you still disagree, you can appeal to the tax tribunal, usually within 30 days of the date on the review result letter. You can appeal online or on form T240.

If you have appealed against a penalty, you do not have to pay it until your appeal has been settled. You can still be charged interest on any tax in dispute.

Why Send It by Post

Your appeal must be in writing and within 30 days. A tracked letter gives you a dated record of when it reached HMRC, and your copy shows exactly what you said.

If you need a signed copy, print it, sign it and send it with Upload a PDF.

Making Tax Digital

From the tax year you join Making Tax Digital for Income Tax, new penalties replace the late filing and late payment penalties on this page. Your 2025 to 2026 tax return, due by 31 January 2027, is still under the current rules.