How to Appeal a Self Assessment Tax Penalty

Your step-by-step guide to challenging HMRC penalties and protecting your rights

Quick Answer

You can appeal an HMRC Self Assessment penalty by writing to HMRC within 30 days, explaining your reasonable excuse. Common reasons include illness, death in family, or reliance on professional advice. Appeal early—you have limited time, and HMRC must give valid reasons for any penalty.

What Is a Self Assessment Tax Penalty?

HMRC can impose penalties for late, incorrect, or unpaid Self Assessment returns. Penalties include fixed amounts (e.g., £100 for being 3 months late) or percentages of unpaid tax (5–100% depending on severity and behaviour). The amount depends on how late you are and whether the error was deliberate.

The good news: HMRC must issue a formal Notice of Assessment explaining the penalty. If you disagree, you have legal rights to appeal.

How to Appeal: Step-by-Step

Step 1: Gather your evidence. Collect documentation supporting your case (medical records, correspondence with accountants, proof of circumstances beyond your control). Your "reasonable excuse" must be clear and credible.

Step 2: Write to HMRC within 30 days. Address the Notice of Assessment to the HMRC office shown on the letter. Explain why the penalty is unfair, reference the specific legislation, and attach evidence. Keep a copy for your records.

Step 3: Wait for HMRC's review. HMRC has 30 days to respond. If they uphold the penalty, you have 30 days to request an independent review.

Step 4: Request an independent review or appeal to the tribunal. If HMRC declines your appeal, request a review by a different HMRC officer. If that fails, you can appeal to the Tax Tribunal—a formal hearing where both sides present evidence.

What the Law Says
Taxes Management Act 1970 (TMA 1970), sections 93–100
Covers appeals to HMRC and the tax tribunal. Section 93 grants you the right to appeal within 30 days. Section 98 allows appeals based on a reasonable excuse.
Finance Act 2009, Schedule 56
Defines "reasonable excuse" in detail. Illness, force of circumstance, and reasonable reliance on professional advice all qualify. Mere forgetfulness does not.
HMRC Factsheet CC/FS13
Official HMRC guidance on late payment penalties and appeals. Available on the HMRC website; clearly states deadlines and evidence requirements.
What counts as a "reasonable excuse"? +

Reasonable excuses include: serious illness (especially unexpected), death of a close family member, force of circumstance you couldn't foresee, and reasonable reliance on professional advice. HMRC guides against "I forgot" or general business pressure. Be specific and provide evidence.

What's the 30-day deadline? +

You must appeal within 30 days of the Notice of Assessment. This is strictly enforced. If you miss it, you lose the right to appeal (unless you can show a good reason for the delay). Mark the deadline on your calendar and submit early.

Can I appeal if my accountant made the mistake? +

Yes, if you can show you reasonably relied on their advice and had no reason to suspect it was wrong. However, if you ignored their warnings or knew there was an issue, reliance may not be reasonable. You may also have a claim against the accountant separately.

What happens if HMRC rejects my appeal? +

You can request an independent review (internal reconsideration) within 30 days. If that is also rejected, you have the right to appeal to the First-tier Tribunal (Tax Chamber)—an independent court. The tribunal will hear both sides and make a binding decision.

Do I need a tax advisor to appeal? +

Not legally required, but highly recommended if the penalty is large or the circumstances complex. An experienced tax advisor or tax lawyer can strengthen your case and represent you at tribunal. Many offer free initial consultations.

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