Self Assessment Penalties: How to Avoid Them and What to Do If You Get One

Self Assessment penalties can add up quickly if you are not careful. Understanding what triggers them, how much they cost, and how to appeal is essential for every sole trader.

Late Filing Penalties

If you miss the 31 January online filing deadline:

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

Maximum penalty for being 12+ months late: £100 + £900 + 5% + 5% of tax due, plus any late payment penalties on top.

Late Payment Penalties

If you do not pay your tax by 31 January:

| Time late | Penalty | |-----------|---------| | 30 days late | 5% of tax unpaid | | 6 months late | Additional 5% of tax still unpaid | | 12 months late | Additional 5% of tax still unpaid |

Interest is also charged from the due date at the Bank of England base rate plus 2.5%.

Inaccuracy Penalties

If your return contains inaccurate figures:

• Careless error: 0–30% of the additional tax due
• Deliberate error: 20–70% of the additional tax due
• Deliberate and concealed: 30–100% of the additional tax due

Penalties are reduced if you tell HMRC about errors voluntarily rather than waiting for them to discover the mistake.

How to Avoid Penalties

File early. Do not wait until January. If your records are up to date, you can file as early as 6 April after the tax year ends.

Set reminders. Mark key dates in your calendar with alerts well in advance.

Use software. Accounted tracks your records throughout the year and reminds you when it is time to file.

Pay on time. Set up a budget payment plan with HMRC to spread the cost throughout the year, or use your software's tax estimate to set money aside monthly.

Check your figures. Review your return carefully before submitting. Common errors include wrong UTR, missing income, and miscategorised expenses.

What to Do If You Get a Penalty

1. Check the Penalty Is Correct

Verify the dates, the amount, and whether you actually filed or paid late. Mistakes do happen.

2. Appeal If You Have a Reasonable Excuse

Reasonable excuses include:

• Serious illness or hospitalisation
• Death of a close family member
• Fire, flood, or theft affecting your records
• HMRC service issues preventing you from filing
• Unexpected hospital stay

You have 30 days from the penalty notice to appeal. You can appeal online through your Government Gateway account or by post.

3. Pay the Penalty (Even If Appealing)

HMRC recommends paying the penalty while your appeal is being considered. If your appeal is successful, you will receive a refund. If you do not pay and your appeal fails, interest will have accrued.

4. Ask for a Time to Pay Arrangement

If you cannot afford the penalty or your tax bill, contact HMRC's Self Assessment helpline to discuss a Time to Pay arrangement. They may let you spread payments over several months.

Prevention Is Always Better

The easiest way to avoid penalties is to stay on top of your records throughout the year. If your bookkeeping is up to date, filing your return is quick and stress-free — no last-minute panic, no missed deadlines.

Stop dreading your Self Assessment. Accounted tracks everything throughout the year so January is just a click, not a crisis. Try it free.