How to Appeal a Self Assessment Penalty: SA370, Reasonable Excuse and the Tribunal (2026/27)

This guide is general information, not advice.

This is for anyone who has received a Self Assessment penalty notice for filing late or paying late and thinks it should not stand: a genuine reason, a wrong penalty, or no need to be in Self Assessment at all.

By the end you will know the deadline, the route (online or form SA370), what GOV.UK says will and will not count as a reasonable excuse, how the review and the tribunal fit together, and whether to pay in the meantime.

Before you start

HMRC’s appeal guidance lists what you need:

• the date the penalty was issued;
• the date you filed the return, if you have;
• the date you paid the tax, if you have;
• details of your reasonable excuse for filing late or not paying on time.

Form SA370 also asks for the tax reference shown on the penalty notice, your National Insurance number if known, the tax year, and for each penalty its amount and the date of the notice, which it says is at the top of the front page of your SA326D or SA370 notice of penalty assessment. Online, you need your Government Gateway sign-in.

For computer problems, GOV.UK’s Disagree with a penalty page says to include the date you tried to file or pay online and any system error message.

Step-by-step

1. Check whether you needed to file at all. HMRC’s guidance says you can ask it to cancel a penalty if you do not need to send a Self Assessment tax return. That is a different request from an appeal.

2. File the return and pay the tax now, if you have not. Form SA370’s own instruction: “If you have not already done so, send us your tax return and pay any tax you owe now, to avoid further penalties.” GOV.UK’s reasonable excuses page adds that you must send your return or payment as soon as you are able to.

3. Use HMRC’s appeal tool to pick the route. From the appeal guidance select Start now. It asks whether you are an individual or in a partnership, then either lets you appeal online or gives you form SA370 (SA371 for a partnership) to post.

4. Give the reason, with dates. The GOV.UK penalty page says to explain why the return or payment was late, including dates, with your name and reference number such as your UTR. On SA370 you tick one of: ill health, postal issues, fire, flood or other natural disasters, did not receive the return, theft or crime, bereavement or death of a close relative, information technology difficulties, or “other acceptable excuse” with an explanation, providing evidence where possible.

5. Send it within 30 days. GOV.UK: “You usually have 30 days from the date your penalty was issued to contact HMRC or make an appeal. If you miss the deadline, you’ll need to give a reason.” The form goes to Self Assessment, HM Revenue and Customs, BX9 1AS “within 30 days of the date shown on the front of your penalty notice”; “late appeals may be accepted if you explain the reason for the extra delay”. Sign and date it, stating the capacity if you sign for someone else.

6. If HMRC refuses, take the review or go to the tribunal. See below for how the two fit together.

Deadlines and what happens next

What HMRC accepts. GOV.UK’s reasonable excuses page defines one as “something that stopped you meeting a tax obligation for a valid reason” and gives this list of what may count:

• your partner or another close relative died shortly before the tax return or payment deadline
• you had an unexpected stay in hospital that prevented you from dealing with your tax affairs
• you had a serious or life-threatening illness
• your computer or software failed while you were preparing your online return
• issues with HMRC online services
• a fire, flood or theft prevented you from completing your tax 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

And what will not be accepted:

• your cheque bounced or 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 tax return

After you appeal. Per Disagree with a tax decision, the case worker looks at the case again and aims to reach agreement; “most disagreements are resolved this way”. If not, you are offered a review. For reply times HMRC points to its reply-times tool, updated weekly; it publishes no fixed figure.

Review or tribunal. You get 30 days from the date of the offer to accept the review or appeal to the tribunal. You can also ask for a review at any time after appealing, by writing to the same HMRC office. GOV.UK’s Get a review page says reviews “usually take 45 days”, are done by a review officer in a different team, and end with the decision upheld, varied or cancelled. If you have asked for a review you must wait for the outcome before going to the tribunal; after it you have 30 days from the date on the review result letter.

The tribunal. Per Appeal to the tribunal, you appeal to the First-tier Tribunal (Tax) online, with a scan or photo of the notice or review conclusion letter and your reasons, or by post on form T240. The deadline is usually 30 days from the date on the decision letter; a late appeal needs an explanation and a judge decides whether to accept it. Not every case has a hearing, but you can ask for one, with at least 14 days’ notice.

Paying in the meantime. GOV.UK’s Delay payment page: “If you’ve appealed against a penalty, you will not have to pay until your appeal has been settled”, and the same applies during a review or tribunal appeal. HMRC’s SA370 guidance still says to consider paying: if the appeal is rejected you pay interest on the penalty from the date it was due; if it succeeds HMRC repays with interest from the date you paid. Outside an appeal, a penalty is due within 30 days of the date on the notice.

The penalties you are appealing. Per the GOV.UK penalties page, late filing brings an initial £100, then after 3 months £10 a day up to £900, after 6 months a further 5% of the tax due or £300 (whichever is greater), and after 12 months another 5% or £300. Late payment brings 5% of the tax unpaid at 30 days, 6 months and 12 months, plus interest. Form SA370 has a box for each stage, so appeal each notice you hold.

Making Tax Digital. From the tax year you are required to use Making Tax Digital for Income Tax, a separate regime applies: penalty points with a 4-point threshold and a £200 penalty, and late payment penalties scaled by delay. HMRC says the penalty letter will tell you how to appeal. Our MTD penalty points guide covers it.

Common mistakes

• Appealing on affordability. Not having enough money is on GOV.UK’s list of excuses that will not be accepted. If the problem is paying, the answer is a Time to Pay arrangement, not an appeal.
• Appealing before filing. The excuse has to explain a delay that has ended. Send the return, then appeal.
• Missing the 30 days and not explaining why. A late appeal is possible, but only with a reason for the extra delay.
• Going to the tribunal first. GOV.UK says you must appeal direct tax decisions to HMRC before you can appeal to the tribunal.
• Appealing one notice when you hold three. Each penalty stage carries its own notice and date.

Worked example

A sole trader’s 2025/26 return was due on 31 January 2027. A notice of the £100 late filing penalty is dated 17 February 2027.

• 30 days from the date of issue runs to 19 March 2027: the appeal needs to be in by then, or a reason given for the delay.
• She files the return on 20 February 2027, then appeals citing an unexpected hospital stay from 25 January to 12 February, with the discharge letter.
• HMRC refuses and offers a review; she accepts within the 30 days. The review “usually” takes 45 days.
• If the review upholds the penalty, she has 30 days from the date on the review result letter to appeal to the tribunal, attaching the review conclusion letter.
• Throughout, she is not required to pay the £100. If she loses, interest runs on it from the original due date; if she pays now and wins, HMRC repays it with interest.

Related reading

• HMRC penalties guide - the full penalty regimes for Self Assessment, VAT, PAYE and Corporation Tax, with the statutory background.
• MTD penalty points 2026/27 - the points-based regime that replaces these penalties once you are in Making Tax Digital for Income Tax.
• How to set up a Time to Pay arrangement with HMRC - if the real problem is paying rather than the penalty.