The UK tax return deadline is 31 January for online returns (31 October for paper returns). HMRC operates a stepped penalty system that becomes increasingly punitive the longer you delay filing your self-assessment return. Here is the full penalty schedule:
Day 1 After Deadline (1 February)
An automatic fixed penalty of £100 applies immediately — even if you owe no tax, have already paid all your tax, or your return shows a refund is due. There is no discretion on this initial penalty.
After 3 Months (30 April / 1 May)
Daily penalties of £10 per day begin, capped at 90 days maximum. This adds up to £900 maximum over the 3-month period. HMRC must notify you before daily penalties begin.
After 6 Months (31 July)
A further penalty of whichever is greater: £300, or 5% of the tax due on the return. For tax bills above £6,000, the 5% surcharge exceeds the £300 minimum.
After 12 Months (31 January following year)
A second penalty of whichever is greater: £300 or 5% of the tax due. In cases of deliberate concealment, this can rise to 70–100% of the tax due.
Maximum Fixed Penalties (excl. interest) if 12+ Months Late
£100 + up to £900 daily + £300/5% at 6 months + £300/5% at 12 months, before interest charges
Plus: Interest on Unpaid Tax
On top of fixed penalties, HMRC charges interest on any tax not paid by 31 January. The current rate is the Bank of England base rate + 2.5% (approximately 7% per annum as of February 2026). Interest accrues daily from the payment due date until settlement.
HMRC Penalty Calculator
Estimate your total late filing and payment penalties. Enter your tax owed and how many months late your return is.
Estimated HMRC Penalty Breakdown
You have the right to appeal against an HMRC self-assessment penalty if you have a reasonable excuse for filing or paying late. You must appeal within 30 days of the penalty notice date.
How to Submit Your Appeal
- Online: Log in to your HMRC online account (Personal Tax Account or Business Tax Account) and navigate to 'Appeal a penalty'
- By post: Write to the Self Assessment address on your penalty notice, including your UTR number, the penalty reference, and your grounds for appeal
- SA370 form: Use this specific HMRC form to appeal self-assessment penalties
Valid Reasonable Excuses
- Serious illness or hospitalisation (you or partner)
- Bereavement of a close relative near the deadline
- HMRC system failures (document the error)
- Natural disaster or flood affecting your home/business
- Unexpected postal delays (Royal Mail strike etc.)
- Software failure that could not be anticipated
- HMRC delay in providing information you needed
Not Accepted as Excuses
- Forgot the deadline
- Thought your accountant had filed it
- Found the online system too difficult
- Too busy with work
- Didn't realise you needed to file
- Couldn't afford to pay (still must file)
- Relied on someone else who let you down
Key Appeal Rule: File First, Appeal Later
HMRC expects you to file your return as soon as possible, even if late. Penalties continue to accumulate while a return is outstanding — even during an appeal. File immediately, pay what you can, then appeal the penalty separately.
Special Relief for Unrepresented Taxpayers
HMRC also has a discretionary "special circumstances" power to reduce penalties where the penalty would be disproportionate or where exceptional circumstances exist that do not meet the strict "reasonable excuse" test. This is harder to obtain but worth requesting if your case is unusual.
First-Offender Leniency
HMRC introduced a Time-to-Pay arrangement to help taxpayers who can't afford to pay their full tax bill. Agreeing a TTP arrangement before the deadline can prevent surcharges from applying, though interest on the outstanding balance continues. Contact HMRC's Payment Support Service on 0300 200 3835 before the deadline if you cannot pay in full.
It is crucial to understand that late filing and late payment attract separate penalty regimes. You can receive both types simultaneously if you file late AND have unpaid tax.
Late Payment Surcharges
If you filed your return on time but did not pay the tax owed by 31 January, HMRC charges:
- 5% surcharge if unpaid after 30 days (by 2 March)
- Further 5% surcharge if unpaid after 6 months (by 31 July)
- Further 5% surcharge if unpaid after 12 months (by 31 January the following year)
- Interest at Bank of England base rate + 2.5% from 1 February onwards
Example: £5,000 Tax Bill Filed and Paid 9 Months Late
- Late filing penalty: £100
- Daily penalties (90 days × £10): £900
- 6-month surcharge (5% of £5,000): £250
- Late payment surcharge (5% at 30 days): £250
- Interest (9 months at ~7%): £262
- Total additional cost: approximately £1,762 on a £5,000 tax bill
Payment on Account Penalties
If you miss a payment on account deadline (31 January or 31 July), HMRC does not immediately issue penalties — but interest does accrue from the due date. A 5% surcharge applies if amounts remain outstanding 28 days after the payment deadline.
Correcting Errors on Your Return
If you submitted your return but made an error, you have 12 months from the original filing deadline to amend it — so until 31 January 2027 for a 2024-25 return. Amending a return is different from filing late and does not trigger additional late filing penalties.