HMRC Penalty Calculator
Ellie SleightholmUse this HMRC penalty calculator to work out exactly what a late Self Assessment return or late tax payment will cost you, including late filing penalties, late payment penalties, and daily interest at the current 7.75% rate. It covers multiple tax years at once and includes a voluntary disclosure mode for income you have never told HMRC about.
If you are worried
If you have arrived here worried, one thing before the numbers. HMRC's penalty system looks frightening on paper, but penalties are routinely reduced, suspended, or cancelled entirely, especially when you come forward before HMRC comes to you. This page shows you what you are facing and, just as importantly, what people actually do about it.
Step by step
How to Use This Calculator
- 1
Pick your situation
Filed late, paid late, did both, or never told HMRC about the income at all. Each is charged differently.
- 2
Enter the tax due for each year
If you are catching up on several years, add each one, and the calculator stacks them, penalties and interest included.
- 3
Say how late you are
Enter your filing and payment dates, and the calculator applies the exact penalty stages you have crossed and counts the days of interest.
- 4
For undeclared income, describe the situation honestly
Whether the failure was a genuine mistake or deliberate, and whether you are coming forward or HMRC contacted you first. The penalty ranges differ enormously.
Filing late
Late Filing Penalties for Self-Assessment
Miss the 31 January online filing deadline, and the charges build in four stages:
Stage 1 · How late
1 day
£100 fixed, even if you owe no tax at all
Stage 2 · How late
3 months
£10 a day for up to 90 days (maximum £900)
Stage 3 · How late
6 months
5% of the tax due, or £300 if that is higher
Stage 4 · How late
12 months
Another 5% or £300, whichever is higher
Two things surprise people here
First: the ladder runs on the return, not the tax
Filed a year late, zero tax bill
- Fixed penalty
- £100
- Daily penalties
- £900
- 6-month charge
- £300
- 12-month charge
- £300
Second
Paying on time does not stop filing penalties
The return and the payment are treated as completely separate obligations.
Paying late
Late Payment Penalties
Pay your tax bill late, and a second, separate set of charges applies to the unpaid amount:
| How late | Penalty |
|---|---|
| 30 days | 5% of the tax still unpaid |
| 6 months | A further 5% |
| 12 months | A further 5% |
One genuinely useful escape route
Set up a Time to Pay arrangement with HMRC before a penalty date and stick to it, and the late payment penalties stop accruing.
Interest continues, but a payment plan agreed before day 30 avoids the first 5% entirely. You can set one up online for most self-assessment debts without speaking to anyone.
Interest
Interest: The Charge You Cannot Appeal
On top of penalties, HMRC charges interest on unpaid tax from the day after the deadline until the day you pay. The rate is the Bank of England base rate plus 4%, which makes it 7.75% from 9 January 2026. It is simple interest, calculated daily, and it also runs on unpaid penalties themselves.
- From 9 January 2026 (base rate + 4%)
- 7.75%
- A day on a £5,000 bill
- £1.06
Over a full year on £5,000
≈ £388
Penalties
Behavioural charges that can be appealed, reduced, or suspended.
Interest
Just the cost of holding money that HMRC regards as theirs, and it is essentially never waived, even with a perfect excuse.
Treat interest differently from penalties in your head.
Real numbers
Worked Example: One Return, One Year Late
You owe £5,000 for a return and payment that are both 12 months late:
£5,000 tax · 12 months late
What the lateness costs
- Filing penalties: 100 + 900 daily + 300 + 300
- £1,600
- Payment penalties: 5% three times on £5,000
- £750
- Interest across the year at 7.75%
- ≈ £388
The 5% tax-geared charge is £250, so the £300 minimum applies at both stages.
Making Tax Digital
New Penalty Rules From April 2026
If you have joined Making Tax Digital for Income Tax, which became mandatory in April 2026 for self-employed people and landlords earning over £50,000, a different regime applies to you.
Late submissions
Penalty points, not instant fines
Late submissions earn penalty points rather than instant fines, with a £200 penalty when you reach four points, and HMRC is running a soft landing for the first year: no points for the first four missed quarterly updates.
Late payment
Sharper for long delays
Day 15
3%
Day 30
+3%
Day 31+
10% a year
Late payment is charged at 3% on day 15, another 3% on day 30, then 10% a year from day 31, which is sharper than the old system for long delays.
Undeclared income
Never Told HMRC About the Income? Read This First
If you have income HMRC does not know about, perhaps a side business that crossed the £1,000 trading allowance years ago, you are in the failure to notify regime, and it works very differently. The penalty is a percentage of the unpaid tax, set by two things: your behaviour and who moved first.
| Behaviour | You came forward (unprompted) | HMRC contacted you (prompted) |
|---|---|---|
| Genuine mistake (non-deliberate) | 0% to 30% (minimum 10% if disclosed 12+ months after the tax was due) | 10% to 30% (minimum 20% if 12+ months) |
| Deliberate | 20% to 70% | 35% to 70% |
| Deliberate and concealed | 30% to 100% | 50% to 100% |
What actually works
How to Get Penalties Reduced or Cancelled
There is a well-worn path here, and it works far more often than people expect:
Step 1
Get the calculation first
Ask HMRC for the detailed breakdown, so you know what the penalty is, what the interest is, and what is simply tax or payments on account. People regularly discover the scary number is mostly the tax they have always owed.
Step 2
File any missing returns immediately
Estimated assessments and determinations often shrink once real figures replace HMRC's guesses, and filing freezes the filing penalty ladder.
Step 3
Contact HMRC and ask for help, not a fight
By phone or webchat, explain the situation plainly. Frontline staff can and do waive penalties for honest situations, and a Time to Pay plan stops late payment penalties accruing.
Step 4
Appeal within 30 days if you have a reasonable excuse
Serious illness, bereavement, HMRC system failures, and other events outside your control all qualify. Not knowing the rules generally does not, but first offences with honest explanations succeed surprisingly often.
Step 5
Get help if it is heavy
An accountant for complex cases, or TaxAid, a charity that helps people on lower incomes deal with tax problems, including negotiating penalties during hardship or mental health difficulties.
Questions
Frequently Asked Questions
Do I get the £100 fine if I owe no tax?
Yes. The late filing penalty is triggered by the return being late, not by owing money. A nil return filed 12 months late still accumulates £1,600 of filing penalties, which is why filing on time matters even in years you earned little.
Can I appeal an HMRC penalty?
Yes, within 30 days of the date on the penalty notice, online through your tax account or by post. You need a reasonable excuse that existed at the deadline and lasted until you filed or paid. Appeals with genuine grounds succeed regularly. Interest cannot be appealed.
Is there an official HMRC penalty calculator?
HMRC has an online tool for estimating self-assessment penalties, though users frequently report it failing to load or being hard to follow, which is exactly why this calculator exists. Ours runs instantly in your browser with no login and works on any phone, so there is no app to download.
Can I pay HMRC penalties in instalments?
Yes. Penalties and interest can be included in a Time to Pay arrangement alongside the tax. Most self-assessment debts under £30,000 can be set up as an online payment plan without calling anyone.
What if I have not filed for several years?
File the oldest years first and work forward, or use the Digital Disclosure Service if you were never registered. Register for self-assessment as soon as possible, since the registration deadline is 5 October after the end of your first tax year of trading.
If your side income sits alongside a normal job, our sole trader vs limited company calculator shows how that self-employment is taxed on top of your salary.
Are VAT penalties the same?
No, VAT has used a points-based system since 2023: late returns earn points, with a £200 penalty at the threshold and late payment charges of 3% at day 15 and day 30, then 10% a year. If you are behind on VAT as well as self-assessment, treat them as two separate problems with separate deadlines.
Will HMRC really be lenient if I come forward?
For honest mistakes, genuinely yes. Unprompted disclosure of a non-deliberate failure sits in the lowest penalty band, which starts at zero percent, and waivers are common when someone corrects the record before HMRC asks. The interest and the original tax always remain payable, but going to HMRC before they come to you is the single biggest factor you control.