How to Appeal a Self Assessment Penalty: Late Filing or Payment
HMRC sends a penalty notice when a return or payment is late. If you had a reasonable excuse, or the penalty is wrong, you can appeal. Here are HMRC's own rules for doing it.
Written and reviewed by James Whitfield · Last reviewed 3 November 2026 · Checked against 2026/27 HMRC rates · Editorial standards · Methodology
You usually have 30 days from the date your penalty was issued to appeal.1 Use HMRC's online tool to appeal online, or download form SA370 or SA371 to appeal by post; have ready the date of the penalty, the dates you filed and paid, and your reasonable excuse.2 Consider paying the penalty while you appeal: if the appeal fails you pay interest on it, and if it succeeds HMRC repays it with interest.2 If HMRC doesn't change its decision, you can ask for a review or go to the tax tribunal.1
- →Deadline: usually 30 days from the date the penalty was issued; later, and you need to give a reason.1
- →Reasonable excuses can include a bereavement, a hospital stay, serious illness, computer or HMRC online service failures, fire, flood or theft.3
- →Not accepted: not having the money, finding the system too difficult, no reminder, or a mistake on the return.3
- →Send the return or payment as soon as you are able to.3
- →Don't need to file at all? Ask HMRC to cancel the penalty instead.2
Related: Check the penalty with our calculator · Self Assessment deadlines · Can't pay your tax bill?
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Check the penalty is right first
For the 2025/26 return, a return filed online after 31 January 2027 gets £100, then £10 a day for up to 90 days from three months after the deadline, then 5% of the tax due or £300 at six and twelve months. Tax paid late gets 5% of the amount unpaid at 30 days, six months and twelve months.4 Our penalty calculator works out which of these apply to your dates. If HMRC has used the wrong dates or the wrong amount of tax, that is a reason to appeal in itself.1
If you registered after 5 October, HMRC should have given you a filing deadline 3 months from the date of its letter or email; a late filing penalty before that date would be wrong.5
What counts as a reasonable excuse
GOV.UK describes a reasonable excuse as something that stopped you meeting a tax obligation for a valid reason. Its examples include: your partner or another close relative died shortly before the deadline; an unexpected stay in hospital; a serious or life-threatening illness; your computer or software failed while you were preparing your online return; problems with HMRC's online services; a fire, flood or theft; postal delays you could not have predicted; delays related to a disability or mental illness; being unaware of or misunderstanding your legal obligation; or relying on someone else to send your return when they did not.3
These will not be accepted: your cheque bounced or payment failed because you did not have enough money; you found HMRC's online system too difficult; you did not get a reminder from HMRC; or you made a mistake on your return.3 Whatever the excuse, you must send the return or payment as soon as you are able to.3
How to appeal
HMRC's appeal page has a tool that checks how to appeal an individual or partnership Self Assessment penalty. From there you can appeal online, or download form SA370 or SA371 and appeal by post.2 You will need the date the penalty was issued, the date you filed your return and the date you paid, if you have, and the details of your reasonable excuse.2
If you could not file or pay because of computer problems, include the date you tried and the details of any error message.1 Be specific about dates: when the problem started, when it ended, and when you filed or paid afterwards.
Should you pay the penalty while you appeal?
HMRC suggests you consider it. If you do not pay and the appeal is rejected, you pay interest on the penalty from the date it was due to the date you pay it. If the appeal is accepted, HMRC repays what you paid, with interest from the date you paid it, as long as you have no other tax to pay.2 Paying first costs nothing if you win and saves interest if you lose.
If HMRC says no
If HMRC does not change its decision or you cannot agree, you will be offered a review by an officer who was not involved. You can also ask for a review at any time after you appeal, by writing to the same HMRC office.1 Reviews usually take 45 days.6 You can take your appeal to the tax tribunal instead; if you have already asked for a review, you wait for its outcome first.1
Frequently asked questions
How long do I have to appeal a Self Assessment penalty?+
Usually 30 days from the date the penalty was issued. If you miss that, you'll need to give HMRC a reason for the delay as well as for the penalty.
Is not having a reminder from HMRC a reasonable excuse?+
No. GOV.UK lists not getting a reminder, finding the online system too difficult, not having enough money and making a mistake on your return as excuses that will not be accepted.
Can I appeal a Self Assessment penalty online?+
Yes. HMRC's appeal tool for individual and partnership Self Assessment penalties lets you appeal online or download form SA370 or SA371 to appeal by post.
Should I pay the penalty before I appeal?+
HMRC suggests considering it. If you lose the appeal you pay interest on an unpaid penalty; if you win, HMRC repays it with interest from when you paid, provided you have no other tax outstanding.
I didn't need to send a tax return. Can the penalty be cancelled?+
Yes. HMRC says you can ask it to cancel a penalty if you do not need to send a Self Assessment return. Tell HMRC as early as possible when you no longer need to file.
What if HMRC rejects my appeal?+
You'll be offered a review by an HMRC officer who was not involved, which usually takes 45 days, or you can appeal to the tax tribunal.
Sources & references
The rates, thresholds and rules in this guide are drawn from the official HMRC and GOV.UK sources below, using the confirmed 2026/27 figures. Each link opens the relevant official page in a new tab.
- Disagree with a tax decision or penalty: penalties www.gov.uk/tax-appeals/penalty
- Appeal a Self Assessment penalty for late filing or late payment www.gov.uk/guidance/check-when-to-appeal-a-self-assessment-penalty-for-late-filing-or-late-payment
- Disagree with a tax decision or penalty: reasonable excuses www.gov.uk/tax-appeals/reasonable-excuses
- Self Assessment tax returns: penalties www.gov.uk/self-assessment-tax-returns/penalties
- Self Assessment tax returns: deadlines www.gov.uk/self-assessment-tax-returns/deadlines
- Disagree with a tax decision or penalty: get a review www.gov.uk/tax-appeals/review-of-a-tax-or-penalty-decision
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