How much will HMRC fine you for
filing or paying late?
Estimate Self Assessment penalties, daily charges, and interest on unpaid tax — and learn how to appeal.
Total Penalty
£0
Estimated total extra charges
Late filing penalties
£0.00
Late payment penalties
£0.00
Estimated interest
£0.00
Total extra charges
£0.00
This is a planning estimate for UK Self Assessment. HMRC may apply additional rules for deliberate withholding, special circumstances, or changed interest rates.
- Self Assessment Penalties
- Fixed charges, daily penalties, and interest HMRC applies when a Self Assessment tax return is filed late, or when the resulting tax bill is paid late. Filing and payment penalties are calculated separately and can stack to substantial amounts.
Self Assessment penalty structure — how the charges escalate
HMRC's penalty regime for late Self Assessment filing is designed to escalate sharply the longer you delay. The penalties are automatic and apply regardless of whether you owe any tax. Understanding the structure is the first step to managing your exposure.
If you miss the 31 January online filing deadline, a £100 fixed penalty is charged immediately – even if you owe no tax or are due a refund. After three months without filing, HMRC adds £10 per day for up to 90 days, meaning a maximum daily penalty of £900. At the six-month mark, a further £300 or 5% of the tax due (whichever is higher) is applied. After twelve months, another £300 or 5% is charged, with HMRC reserving the right to levy up to 100% of the tax owed in cases of deliberate withholding.
| Time after deadline | Penalty | Cumulative maximum |
|---|---|---|
| 1 day late | £100 fixed penalty | £100 |
| 3 months late | £10/day for up to 90 days | £1,000 |
| 6 months late | 5% of tax due or £300 (higher) | £1,300+ |
| 12 months late | 5% of tax due or £300 (higher) | £1,600+ |
Late payment interest and surcharges
Separately from filing penalties, HMRC charges interest on any tax paid after the due date. The late payment interest rate is currently the Bank of England base rate plus 2.5%, making it above 7% in 2025/26. This interest accrues daily from the 31 January payment deadline until the tax is settled in full.
On top of interest, HMRC applies a 5% surcharge on unpaid tax at three separate milestones: 30 days after the payment deadline, six months late, and twelve months late. These surcharges stack – a taxpayer who pays twelve months late faces three separate 5% surcharges (totalling 15% of the unpaid tax) plus daily interest.
| Payment milestone | Surcharge | Interest |
|---|---|---|
| 30 days late | 5% of unpaid tax | BoE base + 2.5% (daily) |
| 6 months late | Further 5% of unpaid tax | Continues accruing |
| 12 months late | Further 5% of unpaid tax | Continues accruing |
Interest is charged from the date the payment was due until the date it is received. You will be charged a penalty if you do not pay on time.
How to appeal a penalty — reasonable excuse rules
You can appeal a late filing or late payment penalty within 30 days of the penalty notice by logging into your HMRC online account or writing to HMRC directly. A successful appeal requires demonstrating a "reasonable excuse" – an unforeseen or exceptional event outside your control that prevented you from filing or paying on time.
HMRC accepts: serious illness preventing you from filing, death of a close relative shortly before the deadline, computer or software failure while filing, HMRC website unavailability, or postal delays for paper returns. What does not count as a reasonable excuse: forgetting, being too busy, relying on an accountant who failed to file on your behalf, or not receiving reminder letters from HMRC.
If your appeal is rejected, you can escalate to a review by a different HMRC officer, or take your case to the First-tier Tribunal (Tax Chamber). The tribunal is independent of HMRC and can overturn penalty decisions. There is no fee to appeal to the tribunal for penalties under £20,000.
Common mistakes that make penalties worse
Many taxpayers turn manageable situations into costly ones through avoidable errors. The five mistakes below are the ones HMRC sees most frequently – and the ones that lead to the highest combined penalty and interest charges.
Filing late instead of not at all. Never skip filing even if you cannot pay – filing stops the penalty clock. The payment interest is a fraction of what filing penalties become.
Missing the appeal window. Penalty appeals must be made within 30 days of the notice. Many taxpayers wait, assume the deadline can be extended, or do not realise an appeal is possible until it is too late.
Assuming a Time to Pay arrangement prevents interest. TTP stops surcharges accumulating but does not eliminate interest on the original unpaid amount. Interest continues to accrue on the outstanding balance throughout the instalment period.
Not registering for Self Assessment on time. You must register for Self Assessment by 5 October following the end of the tax year (e.g., 5 October 2025 for 2024/25). Late registration can itself trigger penalties.
Overpaying to avoid penalties then not claiming a refund. Some taxpayers overpay to avoid surcharges but forget to claim the overpayment back via Self Assessment or by contacting HMRC. HMRC does not automatically issue refunds for excess payments.
Key HMRC deadlines — Self Assessment calendar
Knowing the deadlines is the simplest way to avoid penalties entirely. The Self Assessment calendar runs on a fixed annual cycle. Missing any of these dates triggers automatic consequences – HMRC does not send advance warnings for most of them.
| Date | Deadline |
|---|---|
| 5 October | Register for Self Assessment (new taxpayers) |
| 31 October | Paper tax return filing deadline |
| 31 January | Online filing deadline & tax payment due |
| 31 January | First Payment on Account for following year |
| 31 July | Second Payment on Account |
From April 2026, Making Tax Digital (MTD) for Income Tax adds four quarterly submission deadlines for sole traders and landlords with qualifying income above £50,000. Missing quarterly submissions will trigger a points-based penalty system separate from the annual filing penalties described above.
HMRC: Self Assessment penalties- A £100 penalty applies from day one after the 31 January deadline – even if you owe no tax
- Daily £10 charges begin after 3 months and can reach £900 before percentage-based penalties start
- Late payment surcharges of 5% stack at 30 days, 6 months, and 12 months on top of daily interest
- Always file your return even if you cannot pay – filing stops the penalty clock running
- Appeal within 30 days of a penalty notice if you have a genuine reasonable excuse
- A Time to Pay arrangement stops surcharges but does not stop interest accruing on the outstanding balance
- Register for Self Assessment by 5 October following your first year of self-employment to avoid registration penalties
- From April 2026, MTD quarterly submissions introduce an additional points-based penalty system
Related calculators
HMRC penalty structure
Penalty estimates based on current HMRC Self Assessment penalty rules for 2025/26
Filing + payment view
Estimates include both late filing charges and separate late payment interest and surcharges
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