You missed the 31 January deadline. Or you just opened a letter from HMRC with a £100 fine on it. Either way, you are now in a race against a penalty system that compounds every single month you leave it unfiled.
This page tells you exactly what you already owe, exactly when the next charge kicks in, and exactly what stops it.
The clock is already running
HMRC's penalty system is automatic. There are no warnings before the fines. Every day your return remains unfiled, you are closer to the next threshold. The only thing that stops it is filing the return.
Day 1: The Automatic £100 Fixed Penalty
The moment your return is one day late, HMRC issues an automatic £100 fixed penalty. It does not matter whether you owe any tax. It does not matter if you have never been late before. It does not matter if you had a good reason — that is handled separately through an appeal, after the fine has been issued.
This penalty is applied to your HMRC account automatically, without any letter in advance. Many people discover it weeks later. By then, additional charges may already be accumulating.
3 Months: £10 Per Day — Up to £900 More
If your return is still outstanding three months after the filing deadline, HMRC begins charging £10 for every single day it remains unfiled. This continues for up to 90 days — adding a maximum of £900 on top of the initial £100.
These daily charges do not arrive as 90 separate letters. HMRC calculates the total and issues one notice. But the charges are real and enforceable from the date each day passed.
The daily charges stop the moment you file
If you file at month four, you owe 30 days × £10 = £300 in daily charges. If you file at month six, you owe 90 days × £10 = £900 (the maximum). Filing now — even if you cannot pay — stops the daily charge clock immediately.
6 Months: 5% of Your Tax Bill or £300
At six months overdue, a further penalty applies: 5% of the tax shown as due on your return, or £300 — whichever is higher. For the first time, the size of this penalty is linked to what you actually owe.
How the 6-month surcharge scales with your tax bill
| Tax owed | 5% calculation | Penalty charged (higher of 5% or £300) |
|---|---|---|
| £0 | £0 | £300 |
| £3,000 | £150 | £300 |
| £6,000 | £300 | £300 |
| £10,000 | £500 | £500 |
| £20,000 | £1,000 | £1,000 |
| £50,000 | £2,500 | £2,500 |
12 Months: A Second 5% Surcharge — Plus Enforcement Powers
At twelve months, the exact same 5%-or-£300 surcharge applies again. But at this stage something more serious also becomes available to HMRC: they can issue a determination.
A determination is HMRC's own estimate of what you owe — based on whatever information they have about your income. It is legally enforceable in the same way as an actual tax assessment. You can only challenge it by filing the actual return. Ignore it, and HMRC can pursue it through the courts, instruct debt collectors, or apply for a charging order on your property.
The 12-month point is where enforcement begins
Before 12 months, HMRC sends penalty notices. After 12 months, they begin enforcement action. If you are approaching or past this threshold, professional advice before you make contact with HMRC is strongly recommended.
What You Actually Owe — Full Worked Examples
Total penalty exposure by time overdue (assuming £8,000 tax owed)
| Time overdue | What was charged | Running total |
|---|---|---|
| Day 1 | £100 fixed penalty | £100 |
| 3 months | £900 daily charges (90 × £10) | £1,000 |
| 6 months | £400 surcharge (5% of £8,000) | £1,400 |
| 12 months | £400 second surcharge | £1,800 |
| Throughout | Interest on £8,000 from Jan 31 | £1,800 + interest |
Interest is charged separately on any unpaid tax from the original payment due date. It compounds daily at the Bank of England base rate plus 2.5 percentage points. On £8,000 of unpaid tax, that is roughly £1.50 per day at current rates — £550 per year — on top of everything above.
The One Thing That Stops All of This
Filing the return. That is it. Filing — even without paying the tax owed — immediately stops daily penalties from accumulating further. It removes the risk of a determination. It opens the door to a payment plan. It allows you to appeal penalties already issued.
You do not need complete records to file. HMRC accepts estimated figures, with a note that an amendment will follow. Filing on estimates stops the clock; perfecting the figures can happen over the following weeks.
Stop the daily fines — file within 48 hours
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