UK Self Assessment Late Filing & Payment Penalty Calculator
See HMRC's full £100 → £10/day → 5% / £300 filing ladder plus the 30-day / 6-month / 12-month payment surcharges and late-payment interest, all in one calculation.
31 Jan online, 31 Oct paper.
BoE base rate + 4% since 6 Apr 2025. Check the current HMRC rate if unsure.
Late filing penalties — £830.00
Late payment surcharges — £250.00
HMRC late-payment interest
The four filing penalty stages (Sch 55)
- Day 1 late: £100 fixed, regardless of whether you owe tax.
- 3 months late: £10 per day for up to 90 days — another £900 maximum.
- 6 months late: greater of £300 or 5% of the tax due.
- 12 months late: another greater-of-£300-or-5%, up to 100% of the tax if deliberate and concealed.
Three payment surcharge stages (Sch 56)
- 30 days unpaid: 5% of the unpaid tax.
- 6 months unpaid: another 5%.
- 12 months unpaid: another 5%.
Interest on unpaid tax accrues daily from 1 February at the HMRC published rate (Bank of England base rate + 4% from 6 April 2025). It is separate from the surcharges above and continues until the bill is paid in full.
Filing penalty ladder — how a £5,000 return grows
The filing penalties below apply to the return itself, whether or not you owe tax. The cumulative column assumes £5,000 of tax is due (so the 6- and 12-month stages take the greater of £300 or 5% — here £300 each).
| How late | Penalty added | Cumulative filing penalty |
|---|---|---|
| 1 day late | £100 fixed penalty | £100 |
| 3 months late | £10/day for up to 90 days (+£900) | £1,000 |
| 6 months late | greater of £300 or 5% of tax (+£300) | £1,300 |
| 12 months late | another greater of £300 or 5% (+£300) | £1,600 |
Even a zero-tax return reaches £1,600 after 12 months (£100 + £900 daily + £300 + £300), because the tax-geared stages floor at £300.
Worked example — filed and paid 8 months late
You owe £5,000 on your 2025-26 return and file and pay it on 30 September 2027, eight months after the 31 January 2027 deadline. Using today's HMRC late-payment rate of 7.75%:
| Filing penalties (fixed + 90 days + 6-month) | £1,300.00 |
| Late-payment surcharges (5% at 30 days + 5% at 6 months) | £500.00 |
| Interest (7.75% on £5,000 for 242 days) | £256.92 |
| Total on top of the £5,000 tax | £2,056.92 |
Filing on time (even if you cannot pay) would remove the £1,300.00 filing block entirely — the single biggest saving available, and the reason to submit the return by 31 January regardless of whether you can settle the bill.
Frequently asked questions
How does HMRC calculate Self Assessment late filing penalties?
Four escalating stages under Finance Act 2009 Sch 55: (1) £100 fixed penalty the day after the deadline; (2) from 3 months late, £10 per day for up to 90 days — a further £900 maximum; (3) at 6 months late, the greater of £300 or 5% of the tax due; (4) at 12 months late, another greater-of-£300-or-5% layer, and up to 100% of the tax if HMRC find the failure deliberate and concealed.
How are late payment surcharges different from filing penalties?
Late payment penalties are on the unpaid balancing payment under Sch 56: 5% at 30 days unpaid, another 5% at 6 months, and another 5% at 12 months — 15% in total if the bill sits outstanding for a year. They stack on top of filing penalties and daily interest. Payments on account (31 July) attract interest but not these 5% surcharges.
What is the current HMRC late-payment interest rate?
From 6 April 2025 the HMRC late-payment interest rate is Bank of England base rate plus 4 percentage points (previously base + 2.5%). Interest runs from the day after the payment deadline until the tax is paid in full and is charged daily on the outstanding balance. Check the current gov.uk HMRC interest rates page for today's figure.
What counts as a reasonable excuse?
HMRC accept reasonable excuses such as a recent bereavement, a serious illness, an unexpected stay in hospital, a fire/flood/theft that destroyed records, postal delays outside your control, service issues with HMRC's own systems, or disability-related problems. Reasonable excuse waives filing penalties if the return is submitted without unreasonable delay once the excuse ends — it does not waive interest on unpaid tax.
Can I avoid penalties by filing but not paying?
Yes for the filing penalty ladder (£100 + daily + 5% + 5%), which is tied to the return not arriving. But you will still face the Sch 56 payment surcharges (5% / 5% / 5%) and daily interest on the unpaid tax. Setting up a Time to Pay arrangement with HMRC before the 30-day point usually prevents the first 5% surcharge.
Does the £100 fixed penalty apply if I owe no tax?
Yes. The £100 initial penalty and subsequent daily/tax-geared ladder apply to the return itself — it is triggered by being late, not by owing tax. The tax-geared stages (5% at 6 and 12 months) floor at £300 each, so even a zero-tax return can still accumulate £1,600 in filing penalties after 12 months (£100 + £900 daily + £300 + £300).
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