The Self Assessment late filing penalty explained

Would you rather someone else handled this? Our Self Assessment service means we prepare, check and file your tax return with HMRC on a fixed fee.

How the penalty builds up

1. The day after 31 January. An automatic £100, regardless of whether tax is owed.
2. After 3 months. £10 a day for up to 90 days, adding up to £900.
3. After 6 months. The greater of 5% of the tax due or £300.
4. After 12 months. Another 5% or £300, and more in serious cases where information is withheld.

How to limit the damage

File as soon as you can, because the daily penalties stop once the return is in. If you have a reasonable excuse, such as serious illness or bereavement, you can appeal within 30 days. And filing early next year removes the risk entirely.

The full scale, in order

For anyone still filing an ordinary Self Assessment return, the penalties stack rather than replace each other.

• £100 the moment you miss the deadline. This applies even if you owe no tax at all, and even if you are due a refund.
• 3 months late: daily penalties of £10 a day for up to 90 days, so a maximum of £900 on top of the £100.
• 6 months late: a further penalty of 5% of the tax due or £300, whichever is greater.
• 12 months late: another 5% or £300, whichever is greater.

A return that is a year late with no tax owing therefore costs £1,600 in filing penalties alone. That is the figure that shocks people, and it is entirely avoidable by filing an estimated return on time and amending it later.

If you are in Making Tax Digital, the rules are different

Anyone mandated into Making Tax Digital for Income Tax leaves the £100 regime behind for the tax years they are in it, and moves to a points system.

You get one point per missed deadline. At 4 points you get a £200 penalty, and a further £200 for every subsequent late submission while you sit at the threshold. Points fall away automatically 24 months after the missed deadline, or clear completely once you have filed on time for a set period and everything due in the previous 24 months is in.

Two things worth knowing for 2026/27. There are no penalties for missing a quarterly update deadline this tax year, which is a genuine easing for the first cohort and ends from 2027/28. The annual return deadline does still attract a point.

Reasonable excuse, and what actually works

You can appeal a penalty if you have a reasonable excuse. HMRC accepts things that were genuinely outside your control and that you dealt with promptly once they passed: a serious illness, a bereavement, a fire or flood, an unexpected hospital stay, a service failure at HMRC's end, or software that failed at the point of filing.

What does not work: not knowing the deadline, finding the system too difficult, relying on someone else who let you down, or not having the money. The last one is important. Not being able to pay is not a reasonable excuse for not filing, and the two things are treated completely separately.

Appeal within 30 days of the penalty notice. If you file the outstanding return at the same time, the appeal is far more likely to succeed.

The deadlines themselves

For the 2025/26 tax year, which ended on 5 April 2026: paper returns are due by 31 October 2026 and online returns by 31 January 2027. If you want tax under £3,000 collected through your PAYE code instead of paid in one go, you have to file online by 30 December 2026.

If you have only just started and need to register, the deadline for that is 5 October following the end of the tax year, and the reference you need to file arrives by post about 15 days after you register.

What to do if you are already late

File. Today, not once you have found everything. The daily penalties only start at three months, so there is usually a window where acting quickly caps the damage at £100. Use estimated figures if you must, tick the box to say they are provisional, and amend the return once you have the real numbers. An estimated return filed on time beats a perfect return filed in April.

Frequently asked questions