Late Filing Penalty
How to Appeal a £100 Late Filing Penalty
The £100 late filing penalty is the most common HMRC penalty, affecting over 1 million taxpayers every year. If you had a genuine reason for filing late, you can appeal — and many appeals succeed.
The penalty structure
| How late | Penalty |
|---|---|
| 1 day late | £100 |
| 3 months late | £10/day for 90 days (up to £900) |
| 6 months late | £300 or 5% of tax due |
| 12 months late | £300 or 5% of tax due |
The £100 penalty applies even if you owe no tax. It is triggered automatically by HMRC's systems on 1 February if your Self Assessment return for the previous tax year has not been received by 31 January.
When to appeal
You should appeal if you had a genuine reason for filing late that was beyond your control. Common successful appeals include:
- Illness or hospital stay around the 31 January deadline
- HMRC's online system crashed on or near the deadline (this happens)
- Bereavement of a close family member
- Fire, flood, or theft that destroyed your records
- You didn't know you needed to file — but only if you had a genuine reason, e.g. HMRC failed to notify you
How to appeal
Within 30 days of your penalty notice, submit an appeal online via Government Gateway, by post using form SA370, or by formal letter. Include:
- Your UTR and penalty reference number
- The tax year the penalty relates to
- A clear explanation of your reasonable excuse
- Evidence where possible (medical letters, screenshots, etc.)
- When the excuse ended and when you took action
Success tips
- Be specific about dates and events — vague excuses get rejected
- Explain what you did as soon as the excuse ended
- Cite the legislation: Finance Act 2009 Schedule 55
- Reference Perrin v HMRC [2018] UKUT 156 to show you meet the legal test
- Attach supporting evidence wherever possible
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