Missed the tax deadline? Here's what happens next

If your return is late

• The day after the deadline: an automatic £100 penalty — even if you owe no tax, or have already paid it.
• 3 months late: £10 a day on top, for up to 90 days — a maximum of £900.
• 6 months late: a further £300, or 5% of the tax due if that's higher.
• 12 months late: another £300 or 5%, whichever is higher.

Left a full year, that's over £1,600 in filing penalties alone before any tax — which is why catching it early matters so much.

If your payment is late

Separately, on the tax you owe:

• 30 days late: 5% of the unpaid tax.
• 6 months late: another 5%.
• 12 months late: another 5%.

On top of that, interest is charged daily on anything unpaid from the due date until it's cleared.

Got a good reason?

If something genuinely got in the way — illness, a bereavement, a technical failure — you can appeal the penalty on the grounds of a "reasonable excuse." It's worth doing if your circumstances fit; HMRC does cancel penalties where the reason stacks up.

The quickest way to stop the clock

The daily and percentage penalties keep building until the return is filed and the tax is paid. So the single most useful thing you can do is get it done. That's exactly the kind of catch-up job we handle all the time — send us what you've got and we'll get you straight.