You appeal a Self Assessment late filing penalty by telling HMRC, usually within 30 days of the date the penalty was issued, why it should not be charged. Individuals can do this online or by post on form SA370 (partnerships use SA371), and the appeal succeeds only if HMRC accepts you had a reasonable excuse throughout the period of delay and filed without unreasonable delay once it ended.

Which penalties can be appealed this way?

The online route and forms SA370 and SA371 cover penalties for filing a Self Assessment return late and for paying Self Assessment tax late. HMRC describes its online checker as being for individual and partnership penalties. Other direct tax penalties, such as inaccuracy penalties, are appealed by following the instructions on the penalty letter or by writing to HMRC.

The late filing penalties themselves are set by Schedule 55 to the Finance Act 2009: £100 on the day after the deadline, daily penalties of £10 a day for up to 90 days once the return is 3 months late, and further penalties at 6 and 12 months of the greater of 5% of the tax due and £300. Our page on Self Assessment late filing penalties explains how each one arises. Each penalty is a separate decision, so if several have been charged the appeal should cover all of them.

How long do you have to appeal?

HMRC’s guidance says you usually have 30 days from the date the penalty was issued to contact HMRC or make an appeal. If you miss that deadline you need to give a reason for the delay as well as for the original failure. The rules on accepting a late appeal are covered in our guide to late appeals to HMRC.

An appeal against a Schedule 55 penalty is treated in the same way as an appeal against an assessment to the tax concerned (paragraph 21), which brings in the usual direct tax process of appeal to HMRC first, then an optional review, then the tribunal.

Should you appeal online or on form SA370?

HMRC’s guidance page leads to a checker that tells you how to appeal and lets you either make the appeal online or download form SA370 (individuals) or SA371 (partnerships) to appeal by post. Either route is acceptable. Whichever is used, keep a copy of the appeal and a note of the date it was sent, because the 30 day limit is measured from the penalty notice.

A few points on who can appeal:

  • an agent can appeal or request a review on behalf of a client (CH64540);
  • for a late partnership return, every partner is charged a penalty, but only the representative partner, or a successor, can appeal, and that appeal covers all the partners (CH64540);
  • trustees and personal representatives should follow the instructions on their own penalty notice.

What information does HMRC need?

HMRC’s guidance lists what to have ready before you start:

  • the date the penalty was issued;
  • the date you filed the return, if you have filed it;
  • the date you paid the tax, if you have paid it;
  • details of your reasonable excuse for filing late or paying late.

HMRC’s internal guidance at CH160900 says the burden is on the taxpayer to show a reasonable excuse, and that it is important to explain not just what the problem was, such as an illness, but how it stopped the return being filed. Officers are told to establish the facts from the date the obligation fell due to the date the return was filed. A good appeal therefore gives a dated timeline covering the whole period of lateness, with evidence such as hospital letters, death certificates, software error messages or correspondence with an agent.

What will HMRC accept as a reasonable excuse?

HMRC’s published examples include the death of a partner or close relative shortly before the deadline, an unexpected hospital stay, serious illness, computer or software failure while preparing an online return, problems with HMRC’s online services, fire, flood or theft, unforeseeable postal delays, and delays related to a disability or mental illness. HMRC does not accept that you found the online system too difficult, did not get a reminder, or could not pay because of a lack of money.

The law sets three limits in paragraph 23(2) of Schedule 55:

  • insufficiency of funds is not a reasonable excuse unless it is due to events outside your control;
  • relying on someone else is not a reasonable excuse unless you took reasonable care to avoid the failure;
  • once the excuse ends, you are treated as still having it only if you put the failure right without unreasonable delay.

HMRC applies the four stage approach from the Upper Tribunal case of Perrin (CH160900): establish the facts relied on, decide which are proven, decide whether those facts are an objectively reasonable excuse for this taxpayer and when it ended, and then decide whether the return was filed without unreasonable delay. For reliance on an accountant, HMRC expects you to have explained what was needed, set deadlines and checked progress (CH160700). Our page on reasonable excuse for a late tax return looks at which arguments tend to succeed.

If you were never required to file, the better route is usually to ask HMRC to cancel the return requirement rather than argue an excuse; see telling HMRC you no longer need to file.

Do you have to pay the penalty while the appeal is decided?

No. Paragraph 21(2) of Schedule 55 means you are not required to pay a penalty before an appeal against it is determined. HMRC nonetheless suggests considering paying it: if the appeal is rejected and you have not paid, interest runs on the penalty from the date it was due. If the appeal succeeds, HMRC repays what you paid with interest, provided you have no other tax outstanding.

What happens if HMRC rejects the appeal?

For direct tax penalties, if HMRC does not change its decision you will be offered a review by an officer not involved in the original decision, and you can ask for a review at any time after appealing. Reviews usually take 45 days. You can also appeal to the tax tribunal, normally within 30 days of the review conclusion letter.

On appeal against whether a penalty is due, the tribunal can affirm or cancel HMRC’s decision (paragraph 22). Separately, HMRC may reduce a penalty because of special circumstances, which cannot include ability to pay (paragraph 16).

How might an appeal look in practice?

Illustration only. Priya’s 2024 to 2025 return was due online by 31 January 2026. She was admitted to hospital on 20 January 2026, discharged on 3 March 2026 and filed on 12 March 2026. She received a £100 penalty notice in February.

Her appeal, made online within 30 days of the notice, gives the dates of admission and discharge, explains that she had planned to finish the return in the last week of January, attaches the discharge letter, and shows she filed nine days after leaving hospital. That covers each stage HMRC looks at: a proven event, an objectively reasonable excuse, and a prompt remedy once it ended.

What mistakes weaken an appeal?

  • Describing the excuse without dates, so HMRC cannot see it covered the whole period of lateness.
  • Explaining the problem but not how it stopped the return being filed.
  • Blaming an agent without showing what checks were made.
  • Waiting weeks after the excuse ended before filing.
  • Appealing only the £100 and ignoring the daily or 6 month penalties.
  • Confusing filing penalties with late payment penalties, which need their own grounds.

If HMRC opens a check into your return, tax investigation insurance pays your accountant’s fees. Solar Protect cover pays up to £100,000 with no excess; it never pays tax, interest or penalties. Read how our cover works or get a quote.

Related Accountapedia entries

Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 19 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.