SA370 Appeal Form: How to Cancel an HMRC Self Assessment Penalty (2026)

The SA370 is HMRC's official appeal form for Self Assessment penalties. It is short and looks straightforward. The form itself is rarely the problem. The problem is the grounds section, where most DIY appeals fail because the writing is too vague, too brief, or framed in a way that does not engage with the legal test HMRC actually applies. This guide walks through each part of the form and the content that gives the appeal its best chance.

Two Routes to Submit the SA370

You can submit online through your HMRC Government Gateway account or by paper. Both are equally valid. The online route creates an automatic audit trail and is faster; the paper route lets you attach physical documentation more easily and is the only option for those without a Government Gateway account.

Online Submission

Log into your HMRC account at gov.uk. Navigate to Self Assessment, then to your account summary. Look for "appeal a penalty" in the options for the year and penalty in question. The online form mirrors the paper SA370 exactly. You can save and resume; you can attach scanned PDFs or photographs of evidence.

Paper Submission

Download form SA370 from gov.uk. Complete it in black ink, attach copies (never originals) of supporting evidence, and post to the address on your penalty notice (which varies depending on the type of penalty and your geographic record). Keep a complete copy and send by tracked delivery.

Step 1: Penalty References and Identification

The first section asks for your Unique Taxpayer Reference (UTR), the tax year for which the penalty was issued, the penalty reference number from the notice, and your contact details. All of this is on the penalty notice itself. Get them exactly right; HMRC matches by reference number and a typo in the UTR can route the appeal to the wrong file.

Step 2: Select the Grounds Category

The form provides a list of standard categories: serious illness, bereavement, unexpected hospital admission, computer failure, HMRC error, fire/flood/theft, postal failure, and other. Pick the one closest to your situation. This selection does not determine the outcome on its own; the written grounds do that. But the category should match the substance of what you are about to write.

Step 3: Write the Grounds (The Critical Section)

The grounds section is a free-text field. It is also the part that determines outcomes. A two-sentence response gets rejected almost regardless of the underlying circumstances. A 300 to 500 word grounds section, structured around the three-part test, with specific dates and explicit references to evidence, is what successful appeals look like.

Structure the grounds in this order:

1. 1State the circumstance: what happened, when it happened, with calendar dates.
2. 2Connect it to the test: explain how it was beyond your control and how it actually prevented filing (not just made it harder).
3. 3Address the timeline: when did the circumstance resolve? When did you file? Why was the gap between resolution and filing what it was?
4. 4List the evidence: what is attached and what each piece confirms.
5. 5Acknowledge the procedure: confirm the return is filed, confirm the appeal is within 30 days of the notice (or explain the delay if not).

Avoid bullet points or fragments in the grounds itself; HMRC caseworkers respond to a structured narrative, not a checklist. Avoid emotional language ("I was devastated"); HMRC responds to factual evidence. Avoid generic claims ("I had health problems"); be specific to dates and circumstances.

Step 4: Attach Evidence

Reference each piece of evidence in the grounds text. Generic attachments without explicit reference are easily missed by a caseworker processing many appeals quickly.

Quality matters more than quantity. One specific GP letter with named dates beats five generic letters or three pages of personal narrative. HMRC is looking for documentation that ties directly to the test.

Step 5: Submit and Track

Submit online by clicking through to confirmation. Save the confirmation reference. For paper, send by tracked delivery and keep proof of posting and a complete copy of everything sent.

HMRC aims to respond within 45 days. Enforcement on the appealed penalty is paused during the review. If you have not heard within 45 days, you can chase via the contact number on the rejection letter or via your Government Gateway account.

After You Receive the Decision

HMRC will write back with one of three outcomes: appeal upheld (penalty cancelled), appeal partially upheld (some penalties cancelled and others not), or appeal rejected. If rejected, you have 30 days to request an internal HMRC review, then 30 days from the review outcome to escalate to the First-tier Tax Tribunal.

A rejection is not final. The escalation routes are real and many original rejections are overturned at review or tribunal stage.

Common Questions About the SA370

Can I submit the SA370 if I am outside the 30-day window?

Yes, but you have to first justify the delay before the substantive grounds are considered. Acceptable explanations for a late appeal include the same broad categories as for a late filing (illness, bereavement, postal failure of the original notice). The longer the delay, the higher the bar.

Is there a form for daily penalties or a separate form?

The same SA370 covers daily penalties. List both penalty references on the same form and address the full period in the grounds.

Can I get help with the SA370?

Yes. A tax agent or specialist appeal service can complete and submit it on your behalf. Many offer free initial assessments to identify whether the appeal has realistic prospects before charging for the work.