Calculate exactly what you owe HMRC in late filing penalties, late payment surcharges and daily interest. Know your liability before contacting HMRC or appealing a penalty notice.
HMRC Late Filing & Payment Penalty Calculator
Enter your tax return details to calculate penalties and interest under the self-assessment rules. Select your filing and payment dates — if not yet filed or paid, use today's date.
Filing Penalties
Days filed late—
£100 fixed penalty (1+ day late)—
Daily penalties (£10/day, days 91–180)—
6-month penalty (5% of tax or £300)—
12-month penalty (further 5% or £300)—
Total filing penalties—
Late Payment Penalties
Days paid late—
30-day surcharge (5% of unpaid tax)—
6-month surcharge (additional 5%)—
12-month surcharge (further 5%)—
Total payment penalties—
HMRC Interest on Unpaid Tax
Interest rate (BoE base + 2.5%)~7.75% p.a.
Interest accrued—
Total Liability Summary
Original tax bill—
Total penalties (filing + payment)—
Total interest—
Total amount owed to HMRC—
Extra cost as % of original bill—
This calculator uses self-assessment penalty rules as published by HMRC. Interest rate shown is approximate (7.75% p.a.) — check the current HMRC rate as it changes with the Bank of England base rate. Does not account for appeals, reasonable excuse, or Time to Pay arrangements. Not legal advice.
Self-Assessment Late Filing Penalties
If you miss the self-assessment filing deadline (31 January for online returns), HMRC applies automatic penalties. These are structured in escalating tiers:
How Late
Penalty
1 day late
£100 fixed penalty (regardless of tax due)
3 months late (91+ days)
£10 per day for up to 90 days (max £900 additional)
6 months late (181+ days)
5% of tax due OR £300 — whichever is greater
12 months late (366+ days)
Further 5% of tax due OR £300 — whichever is greater
Example: Tax due of £4,000. Filed 400 days late. Penalties: £100 (day 1) + £900 (days 91–180, 90 × £10) + £300 (6-month: max of £200 or £300) + £300 (12-month: max of £200 or £300) = £1,600 in filing penalties alone.
Self-Assessment Late Payment Penalties
Separate to filing penalties, late payment penalties apply from the day after the tax payment due date:
How Late
Penalty
30 days late
5% of unpaid tax
6 months late (181 days)
Additional 5% of unpaid tax
12 months late (366 days)
Further 5% of unpaid tax
HMRC Interest on Unpaid Tax
In addition to all penalties, HMRC charges late payment interest from the day after the tax due date until the date of payment. The interest rate is set at the Bank of England base rate plus 2.5%. With the current base rate at 5.25%, the rate is approximately 7.75% per annum.
Interest compounds: Interest applies to the outstanding tax amount daily. A £10,000 tax bill unpaid for 2 years would accrue approximately £1,550 in interest at 7.75% per annum — on top of all penalties.
How to Appeal an HMRC Penalty
You have the right to appeal an HMRC penalty if you have a reasonable excuse for the late filing or payment. Submit your appeal in writing within 30 days of receiving the penalty notice. Include:
Your UTR (Unique Taxpayer Reference)
The penalty reference number
A clear explanation of your reasonable excuse
Supporting evidence (medical certificate, death certificate, correspondence)
If HMRC rejects your appeal, you can escalate to the independent Tax Tribunal.
Time to Pay Arrangements
If you cannot pay your tax bill by the deadline, contact HMRC before the payment becomes overdue. A Time to Pay arrangement lets you pay in instalments. You can set one up online for SA debts up to £30,000 without speaking to anyone. Interest continues during the arrangement but penalties may be suspended if you contact HMRC before the penalty date.
Frequently Asked Questions
For self-assessment, if you miss the 31 January deadline: £100 fixed penalty immediately. After 3 months (91+ days late): £10 per day for up to 90 days (maximum £900 additional). After 6 months: an additional 5% of the tax due or £300. After 12 months: a further 5% or £300.
For self-assessment: 30 days late — 5% of unpaid tax. 6 months late — additional 5%. 12 months late — further 5%. HMRC also charges interest at approximately 7.75% per annum on unpaid tax from the due date.
Yes. HMRC charges interest on unpaid tax from the due date until payment. The interest rate is the Bank of England base rate plus 2.5%. Interest accrues daily on the outstanding tax amount, not on penalties themselves.
Yes. You can appeal if you have a reasonable excuse for late filing or payment. Reasonable excuses include serious illness, bereavement, postal failure by HMRC, or serious technical problems with HMRC's own systems. You must appeal within 30 days of the penalty notice.
HMRC considers: serious illness or hospitalisation; death of a close relative; unexpected postal delays; HMRC's own online systems being unavailable; and events genuinely outside your control. Personal financial difficulties or forgetting are generally not accepted.
Contact HMRC before the deadline to arrange a Time to Pay arrangement. If agreed before the payment deadline, late payment penalties may be suspended. HMRC will not waive interest on a Time to Pay arrangement, but penalties can be avoided if you contact them proactively.
Yes. The £100 fixed filing penalty applies even if you owe no tax — the obligation is to file the return. The later percentage-based penalties (5% surcharges) are based on tax owed, so if your tax bill is nil, those particular penalties may be £0.
For the 2024/25 tax year, the balancing payment is due by 31 January 2026. Payments on Account are due 31 January and 31 July. Missing the 31 January payment date triggers late payment penalties after 30 days.
A Time to Pay (TTP) arrangement lets you pay tax in instalments over typically up to 12 months. You can set up a TTP online for SA debts up to £30,000. Interest continues to accrue but penalties can be avoided if TTP is agreed before the penalty date.
Yes. For deliberate errors or evasion, HMRC can charge penalties of up to 200% of the tax due (offshore) or up to 100% for domestic issues. These replace standard penalties and can also lead to criminal prosecution.
HMRC's current interest rate is approximately 7.75% per annum (Bank of England base rate 5.25% plus 2.5%). This equates to approximately 0.0212% per day. Interest accrues from the day after the payment deadline.
Read the notice carefully and check dates and amounts. If you believe the penalty is wrong, appeal in writing within 30 days. If you have a reasonable excuse, state it clearly with supporting evidence. If correct, pay promptly to stop further interest accruing.