Missing the Self Assessment deadline is proving expensive for UK taxpayers.
New figures released by HMRC show that £325 million was paid in penalties and interest last year by individuals who failed to file or pay their tax on time after the thirty one January deadline.
Analysis of HMRC’s published data indicates that around six hundred thousand taxpayers were penalised for late submission or payment.
For anyone with outstanding returns or unpaid tax, this serves as a clear reminder of how quickly costs can escalate.
Penalties for late tax returns and payments
HMRC automatically applies a £100 fixed penalty as soon as the filing deadline is missed, even where no tax is due. Further penalties and interest are added if delays continue.
Late filing penalties
| Date of filing | Penalty |
| One day late | £100 fixed penalty applies even if no tax is owed |
| Three months late | £10 per day penalty for up to ninety days, capped at £900 |
| Six months late | Further penalty of the higher of £300 or five per cent of the tax due |
| Twelve months late | Additional penalty of the higher of £300 or five per cent of the tax due |
| Twelve months late (serious cases) | Up to one hundred per cent of the tax due in very serious cases such as deliberate withholding of information |
Late payment penalties
| How late the payment is | Penalty |
| One day late | Interest charged on the overdue tax at the HMRC interest rate, currently 7.75 per cent |
| Thirty days late | Penalty of five per cent of the unpaid tax |
| Six months late | Additional five per cent penalty of the unpaid tax |
| Twelve months late | Further five per cent penalty of the unpaid tax |
The scale of unpaid tax
HMRC estimates that £8.7 billion of Self Assessment tax remained unpaid for the 2023/24 tax year. This represents 12.5 per cent of the £69.6 billion expected to be collected.
Looking beyond Self Assessment, the total amount of overdue tax across all regimes is now around £44 billion, with most of this already progressing through formal debt collection processes.
In many cases, late payment is not caused by avoidance or refusal to pay, but by poor planning.
Common issues include underestimating the size of a tax bill, weak record keeping and leaving preparation until the final weeks before the deadline. When penalties and interest begin to apply, liabilities can grow rapidly and become much harder to manage.
Getting ahead of future tax deadlines
Regularly setting aside funds during the year and reviewing your position well before the filing deadline can significantly reduce pressure. Early advice also allows time to explore payment options if cash flow is tight.
