How to Appeal a Self Assessment Tax Return Penalty

To appeal a Self Assessment tax return penalty, write to HMRC within 30 days of the date on the penalty notice, explain the reasonable excuse that stopped you from filing or paying on time, and attach evidence backing up your account.¹ You can appeal online through HMRC’s tool or by post using form SA370 for individuals or SA371 for partnerships. If HMRC turns you down, you can ask for a statutory review by a different officer or take the case to the First-tier Tribunal.

The 30-Day Deadline

The clock starts on the date printed on the penalty notice, not the date it arrived. You have 30 days to get your appeal to HMRC.¹ Miss the window and you can still appeal, but you will need to explain in the same letter why the appeal itself is late, and HMRC does not have to accept the late submission.

Penalties you can challenge range from the automatic £100 charge for filing a day late through daily £10 charges after three months, further tax-based percentages at six and twelve months, and separate late payment penalties calculated as a percentage of the unpaid tax.² The appeal process is the same for each. Interest on unpaid tax keeps running whether or not you have an appeal in progress.

What Counts as a Reasonable Excuse

The legal test is that something unexpected and beyond your control stopped you from meeting the deadline, and that you put things right without unreasonable delay once the obstacle passed.³ That second part matters. If a hospital stay ended in March and you did not file until September with no further explanation, the excuse only covers the time you were in hospital.⁴

HMRC guidance says the following circumstances may qualify:

The death of a partner or close relative shortly before the deadline.
An unexpected stay in hospital or a serious illness that stopped you dealing with your tax affairs.
A computer or software failure while you were preparing your return.
Problems with HMRC’s own online services.
Fire, flood, or theft that destroyed records or prevented you from filing.
Unpredictable postal delays where you sent the return in time.
A disability or mental health condition that caused unavoidable delay.

Relying on someone else, such as an accountant, to file on your behalf can also count, but only where you took reasonable care to avoid the failure.⁵

HMRC will not accept:

A payment that bounced because you did not have enough money in your account.
Finding HMRC’s online system too difficult to use.
Not receiving a reminder from HMRC.
A mistake on your tax return.

Lack of funds on its own is not a reasonable excuse unless it was caused by events outside your control.³

What to Have Ready

Pull these together before you start:

Your Unique Taxpayer Reference, the 10-digit number found on previous tax returns, your Self Assessment registration letter, or your HMRC online account.⁶
The penalty reference number, printed on the notice.
The date the penalty was issued, which sets the 30-day clock.
The date you filed your return, if you have, and the date you paid the tax, if you have.⁷
Supporting evidence: doctor’s notes for illness, a death certificate for bereavement, screenshots of error messages for IT failures, or correspondence showing postal disruption.

Write a clear, chronological account of what happened and why it stopped you meeting the deadline. Stick to dates and facts. HMRC officers work through thousands of appeals, and a short, well-evidenced narrative reads better than a long complaint about the penalty itself.

How to Submit the Appeal

Online

HMRC’s online tool walks through the steps: you pick the type of penalty, choose the reason, and type your explanation. Save the confirmation the system produces as proof of submission.⁷

By Post

Download form SA370 for individual penalties or SA371 for partnership penalties, complete it, and post it to the address on the form. Use tracked delivery and keep a photocopy of the signed form with the tracking receipt.⁸

If You Should Not Be in Self Assessment

If you received a penalty but should never have been in Self Assessment, the route is different. Ask HMRC to withdraw the notice to file and cancel the penalty; the online tool covers this scenario.⁷

Should You Pay the Penalty While You Appeal?

HMRC advises paying the penalty even while the appeal is pending. If you leave it unpaid and the appeal fails, interest runs from the original due date to the date you finally pay.⁷ If the appeal succeeds, HMRC repays what you paid plus interest from the date of your payment, provided you have no other outstanding tax debts.

Asking for a Special Reduction

Even without a reasonable excuse, HMRC has the power to grant a “special reduction” where applying the penalty strictly would produce a result that is disproportionate or contrary to the purpose of the penalty. HMRC should consider this separately, after deciding whether a reasonable excuse applies.⁹ Special reductions are not commonly granted, but it is worth raising in your appeal if the penalty feels wildly out of proportion to the failure, because HMRC is required to consider it before finalising the amount.

If HMRC Rejects Your Appeal

An HMRC officer reviews your appeal and either cancels the penalty or writes back explaining why they will not. If the answer is no, you have two further routes.

Statutory Review

A statutory review means a different HMRC officer, one who was not part of the original decision, looks at your case again. You have 30 days from the date on the decision letter to accept HMRC’s offer of a review. The reviewing officer can uphold, vary, or cancel the penalty.¹⁰ Reviews are free and do not involve a hearing. You are not required to have one before going to the tribunal, but it is often worth trying first.

First-tier Tribunal (Tax Chamber)

If the review upholds the penalty, or you choose to skip the review, you can appeal to the First-tier Tribunal (Tax Chamber), an independent judicial body separate from HMRC. You normally have 30 days from the review conclusion letter to lodge the appeal.¹¹ File online or by completing form T240, and include the original penalty notice or review letter along with your reasons. A judge decides the case, and their decision is binding. Most straightforward penalty appeals are handled on paper, though you can ask for an in-person hearing if you want to present the case yourself.

1
GOV.UK. Disagree with a Tax Decision or Penalty
2
GOV.UK. Self Assessment Tax Returns: Penalties
3
legislation.gov.uk. Finance Act 2009, Schedule 55
4
legislation.gov.uk. Taxes Management Act 1970 – Section 118
5
GOV.UK. Disagree with a Tax Decision or Penalty: Reasonable Excuses
6
GOV.UK. Find Your UTR Number
7
GOV.UK. Appeal a Self Assessment Penalty for Late Filing or Late Payment
8
HM Revenue and Customs. Self Assessment: Appeal Against Penalties for Late Filing and Late Payment
9
GOV.UK. CH170100 – Special Reduction: Overview
10
GOV.UK. Disagree with a Tax Decision or Penalty: Get a Review
11
GOV.UK. Appeal to the Tax Tribunal