How to Appeal a £100 Self Assessment Late Filing Penalty

To appeal a £100 Self Assessment late filing penalty, you must file your outstanding tax return immediately to stop further penalties. Next, you must submit an appeal to HM Revenue and Customs (HMRC) within 30 days of the penalty notice online or by post using Form SA370. You must prove that a reasonable excuse prevented you from filing your return on time.

How do I appeal the £100 penalty? Key Takeaways

You can appeal the £100 penalty if you have a valid reason, but you must follow HMRC rules precisely. You must submit your outstanding tax return first to prevent daily penalties from escalating, and file your appeal within 30 days.

• File your outstanding tax return first to stop daily penalties.
• Submit your appeal within 30 days of the date on the penalty notice.
• Provide a valid reasonable excuse that covers the entire delay period.
• Choose between submitting online via GOV.UK or sending Form SA370 by post.
• Request a statutory review or appeal to the First-tier Tribunal if rejected.

Step 1: Check if you must file your tax return first

You must file your outstanding tax return before HMRC will process an appeal.

Step 2: How do I appeal my late filing penalty to HMRC?

You must appeal within 30 days of the date printed on your penalty notice. You can choose to appeal online or send a physical form by post.

1. Submit your outstanding Self Assessment tax return online or on paper.
2. Access the official HMRC online appeal tool on GOV.UK to submit digital details.
3. Alternatively, download and complete Form SA370 from the GOV.UK website.
4. Write a cover letter with your Form SA370 containing your excuse, dates, and evidence.
5. Send your postal appeal to: Self Assessment, HM Revenue and Customs, BX9 1AS.

If you miss the 30-day window, write your appeal as soon as possible. HMRC possesses discretionary powers to accept late appeals if you present a genuine reason for your delay.

What is a reasonable excuse for late filing?

Under the Finance Act 2009, Schedule 55, paragraph 23, a reasonable excuse is an unexpected or unusual event that genuinely prevented you from meeting your tax obligation. This event must be outside of your control, such as a major life disruption or serious accident.

Under UK law, your reasonable excuse must cover the entire period of your delay. Once the excuse ends, you must submit your tax return without any unreasonable delay to remain compliant.

What counts as a reasonable excuse under HMRC rules?

HMRC assesses every appeal case by case using strict definitions. Some situations are universally accepted, whereas administrative errors or general disorganisation are routinely standard grounds for rejection.

Step 3: What if HMRC rejects my penalty appeal?

If HMRC rejects your initial appeal, you can continue to dispute the decision.

1. Request a statutory review under the Taxes Management Act 1970, sections 49B to 49I, which assigns an independent HMRC officer to re-evaluate your case.
2. Submit any new or missing supporting evidence to the independent officer during this statutory review.
3. Appeal directly to the First-tier Tribunal (Tax Chamber) if the statutory review still goes against you.

How to write a successful penalty appeal: key tips

For a successful appeal, you must provide the precise dates when your excuse began and ended. Attach physical evidence such as medical certificates, official death certificates, police crime reference numbers, or dated digital screenshots of HMRC system errors.

Under the Finance Act 2009, Schedule 55, paragraph 18(2)(a), you do not have to pay the £100 penalty while your formal appeal is pending. However, HMRC recommends paying the penalty to prevent interest charges from accumulating if they reject your appeal.