What counts as a reasonable excuse for a late tax return?

HMRC accepts excuses like serious illness, bereavement of a close relative, unexpected hospital stay, postal strikes or delays, HMRC online service outages, fire/flood/theft affecting records, and being unaware of a tax obligation where HMRC failed to notify you. The excuse must have prevented you from filing on time and you must have filed as soon as reasonably possible afterwards.

How long do I have to appeal a self-assessment penalty?

You normally have 30 days from the date on the penalty notice to appeal. You can appeal online through your Government Gateway account, by post using form SA370, or by phone. If you miss the 30-day window, you can still appeal but must explain why the appeal is late.

Can I appeal a late tax return penalty if I forgot?

Simply forgetting is not a reasonable excuse in HMRC's view. However, if there were underlying circumstances that caused you to forget — such as a mental health condition, serious personal crisis, or you had a reasonable belief that you did not need to file — you may still have grounds for appeal.

What happens if HMRC rejects my appeal?

If HMRC rejects your appeal, you can ask for a review by a different HMRC officer. If you disagree with the review outcome, you can escalate to the First-tier Tribunal (Tax Chamber) within 30 days. The tribunal is independent of HMRC.

Do I still need to pay the penalty while appealing?

If you appeal within 30 days, HMRC will normally pause collection of the penalty until the appeal is decided. If you appeal late, you may need to pay first and claim a refund if successful.

Reasonable Excuse for Late Tax Return: HMRC Guide + Appeal Steps (2025/26)

If you've received a penalty for filing your self-assessment tax return late, you might be able to get it cancelled — but only if you have what HMRC considers a reasonable excuse.

This guide covers exactly what qualifies, what doesn't, how to appeal step by step, and includes template wording you can adapt.

What is a reasonable excuse?

A reasonable excuse is something unexpected and outside your control that stopped you meeting a tax obligation on time. HMRC looks at whether a prudent person in your position would have been unable to file.

Both conditions must be met. If you recovered from illness in November but didn't file until February, HMRC will likely reject your appeal.

Excuses HMRC is likely to accept

✅ Generally accepted reasonable excuses:

Serious illness or disability — yours or an immediate family member's, particularly if it required hospital treatment or significantly impaired your ability to manage affairs
Bereavement — death of a partner, close family member, or someone you cared for
Unexpected hospital stay — emergency admission that prevented you from filing
HMRC online service outage — if the service was down close to the deadline and you can demonstrate you tried to file
Postal strikes or delays — for paper returns, if Royal Mail disruptions prevented delivery
Fire, flood, or theft — if your records were destroyed and you needed time to reconstruct them
Reasonable reliance on a third party — if your accountant failed to file despite having everything they needed (but you must have given them adequate time)
Mental health condition — depression, anxiety, or other condition that prevented you managing your tax affairs
HMRC failure to notify — if HMRC did not send a notice to file and you had a reasonable belief you didn't need to

Excuses HMRC will almost certainly reject

❌ Not reasonable excuses:

"I forgot" or "I didn't know the deadline"
"I was too busy with work"
"My computer broke" (unless very close to deadline and you had no alternative)
"I didn't have the money to pay" (you can still file without paying)
"I didn't have all my figures" (you can estimate and amend later)
"My accountant was too busy" (you are responsible for choosing a reliable agent)
"I didn't receive a reminder" (HMRC is not obliged to send reminders)
"I found the process confusing" (help is available)

Self-assessment penalty amounts

How late	Penalty
1 day late	£100 (even if no tax owed)
3 months late	£10/day for up to 90 days (max £900)
6 months late	£300 or 5% of tax due (whichever is greater)
12 months late	£300 or 5% of tax due (in serious cases, up to 100% of tax due)

For the 2024/25 tax year, the filing deadline was 31 January 2026. If you missed it, the £100 penalty was automatic.

How to appeal: step by step

Step 1: Gather your evidence

Step 2: Choose your appeal method

Step 3: Submit within 30 days

You have 30 days from the penalty notice date to appeal. If you miss this window, you can still appeal but must explain the delay.

Step 4: Wait for HMRC's decision

HMRC typically responds within 40 days. During this time, penalty collection is normally paused.

Appeal template wording

Dear HMRC, I am writing to appeal against the late filing penalty for self-assessment tax return [YOUR UTR NUMBER] for the tax year 2024/25. My reasonable excuse: [Describe what happened — be specific about dates, what prevented you from filing, and why you could not have filed sooner.] When the excuse applied: From [DATE] to [DATE]. Action taken once the excuse ended: I filed my return on [DATE], which was [X days] after I was able to do so. Supporting evidence enclosed: [List documents — e.g., "GP letter dated 15 December 2025 confirming diagnosis and treatment period"] I believe this constitutes a reasonable excuse under paragraph 23(1) of Schedule 55 to the Finance Act 2009. I respectfully request that the penalty be cancelled. Yours faithfully, [YOUR NAME] [YOUR UTR] [YOUR ADDRESS]

⚠️ Important: File your tax return as soon as possible, even before the appeal is decided. The longer you wait, the more penalties accumulate — and HMRC is less likely to accept your excuse if you delay further after the obstacle has passed.

What if HMRC rejects your appeal?

Statistics show that a significant proportion of tribunal appeals succeed, particularly where the taxpayer has clear evidence and HMRC's original decision was borderline.

Tips to strengthen your appeal

Related guides

📦 Self-Assessment Sorted: The Getting-Paid Toolkit

Templates, letter wording, checklists, and step-by-step guides for handling HMRC penalties, chasing invoices, and keeping your freelance finances on track.

Get the toolkit — £19 →

Landolio helps UK freelancers and small businesses get paid and stay compliant. Home · Blog · Free tools

Reasonable Excuse for Late Tax Return: HMRC Guide + How to Appeal (2025/26)