Written by the TaxTune Editorial Team · Reviewed by our qualified accountants · Updated for 2026
The quick answer You can appeal an HMRC penalty within 30 days, usually online or on a form such as the SA370 for Self Assessment. If you have a reasonable excuse, such as serious illness, bereavement or a genuine HMRC error, the penalty can be cancelled. You normally need to have put right whatever caused it.

How to appeal, step by step

  1. Act within 30 days. You have 30 days from the date on the penalty notice to appeal.
  2. Put right the cause. File the outstanding return or pay the tax first, as an appeal usually expects this.
  3. Explain your reasonable excuse. Set out clearly what happened and why it stopped you meeting the deadline.
  4. Submit the appeal. Online through your account, or by the relevant form such as SA370, with any evidence.
  5. Escalate if refused. If HMRC rejects it, you can ask for a review or take it to the tax tribunal.

What counts as a reasonable excuse

HMRC accepts genuine, unavoidable reasons: serious illness, a death in the family, a fire or flood, a failure of HMRC systems, or postal delays outside your control. It does not accept simply forgetting, finding the system difficult, or relying on someone else without checking.

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Frequently asked questions

How do I appeal an HMRC penalty?

Appeal within 30 days of the penalty notice, usually online or by a form such as the SA370 for Self Assessment. Explain your reasonable excuse and include evidence, having first put right what caused the penalty.

What is a reasonable excuse?

A genuine, unavoidable reason such as serious illness, bereavement, fire or flood, an HMRC system failure, or postal delays outside your control. Simply forgetting is not accepted.

How long do I have to appeal?

Normally 30 days from the date on the penalty notice. Late appeals are only accepted with a good reason for the delay.

What if HMRC rejects my appeal?

You can ask for an independent review by HMRC, and if still unsuccessful, take the case to the First tier Tax Tribunal.

Do I have to pay the penalty while appealing?

You can usually ask for the penalty to be postponed while the appeal is considered, but interest may still accrue on any unpaid tax behind it.