Self Assessment · late filing & payment penalties

How much is the penalty for a late tax return?

Missed the 31 January deadline — or about to? This works out the HMRC penalty on your Self Assessment: the automatic £100, the £10-a-day charges, the 5% late-payment penalties, and the interest on top. Enter two things and see exactly where you stand.

Work out your penalty

Which tax return is late? The tax year the return covers. Online returns and the tax itself are due the following 31 January.

When did you (or will you) file and pay? Defaults to today. The penalty grows in steps at 3, 6 and 12 months late, so the date matters.

The tax you owe for that year Your Self Assessment bill — Income Tax plus Class 4 National Insurance. Leave as 0 if you owe nothing or are due a refund; the £100 late-filing penalty still applies. Not sure? Estimate it with our free tax calculator first.

I paid the tax on time — only the return is late. (Uncheck if the tax is late too — that's the usual case when you haven't filed yet.)

The penalties, in plain terms

There are two separate sets of charges, and you can get both at once: one for sending the return late, and one for paying the tax late.

Filing late (the return itself)

£100 the moment you miss the deadline — even if you owe no tax, or are owed a refund
After 3 months: £10 a day, for up to 90 days — a maximum of £900
After 6 months: a further 5% of the tax due, or £300 — whichever is greater
After 12 months: another 5% or £300, whichever is greater

Paying late (the tax)

5% of the tax still unpaid at 30 days late
Another 5% at 6 months
Another 5% at 12 months

Interest runs on top — every day

HMRC also charges interest on tax paid late, from the due date until the day you pay. The rate is 7.75% (Bank of England base rate plus 4%), set on 9 January 2026 — check the current HMRC rate, as it moves with the base rate. Interest applies to unpaid penalties too, so clearing the balance quickly is what stops the number climbing.

Got a reasonable excuse?

Penalties can be cancelled if you had a genuine reasonable excuse — a serious illness, a bereavement, a fire or flood, or HMRC service failures, for example. You still need to file and pay as soon as the excuse ends, then appeal the penalty on GOV.UK. The single best way to shrink an unavoidable penalty is to file now: the daily charges and the 6- and 12-month percentages stop growing the day HMRC has your return and payment.

More free tools

What do I actually owe? →Estimate your Income Tax and Class 4 NIC so the penalty maths uses a real figure. Payments on account →The 31 July instalment and how to reduce it without getting caught by interest. Every Self Assessment deadline →Filing and payment dates you can add to your calendar so this never happens again.

Common questions

How much is the fine for a late tax return?

You get an automatic £100 penalty the moment you miss the 31 January online deadline. If the return is more than 3 months late, HMRC adds £10 a day for up to 90 days (a maximum of £900). After 6 months there's a further 5% of the tax due or £300, whichever is greater, and the same again after 12 months.

Is there a penalty if I owe no tax or am due a refund?

Yes. The £100 late-filing penalty applies even if you owe nothing or HMRC owes you money. It's a penalty for the late return, not the late tax. File as soon as you can to stop further charges building up.

What's the penalty for paying my tax late?

On top of any late-filing penalty, HMRC charges 5% of the tax still unpaid at 30 days late, another 5% at 6 months, and another 5% at 12 months. Interest at the current 7.75% rate also runs daily from the due date until you pay.

How much interest does HMRC charge on late tax?

The late-payment interest rate is 7.75% from 9 January 2026 — the Bank of England base rate plus 4%. It's charged daily on the unpaid tax, and on unpaid penalties, from the due date until the balance is cleared.

Can I appeal a Self Assessment penalty?

Yes, if you had a reasonable excuse such as a serious illness, a bereavement, or an HMRC system failure. File and pay as soon as the excuse ends, then appeal the penalty through your online account or with form SA370 on GOV.UK.

When is the Self Assessment deadline?

Online returns and the tax owed are both due by 31 January following the end of the tax year (which runs to 5 April). Paper returns are due earlier, by 31 October. See our free deadlines page for every date.

The cheapest penalty is the one you never get

Every one of these charges starts with not knowing the number in time. Our tax estimator works out your current-year liability — and what to set aside — so 31 January is a payment, not a penalty.

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