What a late tax return will cost you.

Enter your 2025/26 tax bill and the dates you sent the return and paid. We'll work out each HMRC penalty and the interest, to the day.

Uses 2026/27 HMRC rates
Checked 29 Oct 2026 against GOV.UK

1Your tax bill for 2025/26

Tax you owe for the year From your tax calculation, not counting next year's payment on account. Enter 0 if you owe nothing.

2Your tax return

Your deadline to send it

When you sent it, or will send it The date it reaches HMRC.

3Paying the tax

When you paid in full, or will pay The tax is due by 31 January 2027, whatever your filing deadline.

I've agreed a payment plan with HMRCAsked for by 2 March 2027 and kept to.

Penalty docket29 Oct 2026

Your figures print here.

Enter your tax bill and the two dates, then press Work out my penalties. You'll get each penalty, the interest and the next date it goes up.

Every penalty, and when it lands

Sending the return late and paying late are penalised separately. A late return is penalised even if you owe nothing or are due money back. Each date below is the first day the penalty applies if the return still hasn't been sent, or the tax still hasn't been paid.

If still not done on	What's late	Penalty
1 February 2027	Tax return	£100
3 March 2027	Tax	5% of the tax still unpaid
1 May 2027	Tax return	£10 a day for up to 90 days, so up to £900 by 29 July 2027
1 August 2027	Tax return	5% of the tax due or £300, whichever is more
3 August 2027	Tax	Another 5% of the tax still unpaid
1 February 2028	Tax return	Another 5% of the tax due or £300, whichever is more
3 February 2028	Tax	Another 5% of the tax still unpaid

Interest is charged on top, on any tax paid after 31 January 2027. It runs from the next day until you pay, at 7.75% a year since 9 January 2026. HMRC sets it at the Bank of England base rate plus 4%, so it moves when the base rate does.

How the sum works

Daily penalties are counted from the first day after the 3 months, including the day you send the return, and stop at £900. HMRC's letter gives the exact start date.
The 6 and 12-month penalties are 5% of the tax due on the return, or £300 if that's more.
Late payment penalties are 5% of whatever is still unpaid on each date. We assume you pay the whole amount in one go on the date you enter.
Not included: interest on the penalties themselves if you don't pay them within 30 days, and your first payment on account for next year, which picks up interest if it's late but no penalty.

Keeping the cost down

Send the return, even if you can't pay. The filing penalties keep growing until it's in, and you can't know the bill until it is.
Set up a payment plan early. If you ask HMRC for one before the first late payment penalty and keep to it, the late payment penalties don't apply. Interest still does. Our guide to what to do if you can't pay explains how.
Appeal if you had a reasonable excuse. Something that stopped you for a valid reason, such as an unexpected stay in hospital or a close relative dying just before the deadline, can cancel a penalty. You usually have 30 days from the penalty letter to appeal.

Who this fits

These are the penalties for a sole trader's 2025/26 self-assessment return. They apply to everyone sending that return, including people who joined Making Tax Digital in April 2026: the new points-based penalties only start from the tax year you join.

If HMRC has written to say the new penalties already apply to you, because you volunteered for MTD and agreed to them, this calculator doesn't fit. The same goes for partnership returns. From April 2027, the new penalties apply to everyone who sends a personal tax return. How Making Tax Digital works

Sources: Self Assessment tax returns: penalties, Penalties for Making Tax Digital for Income Tax, Disagree with a tax penalty and HMRC interest rates, GOV.UK; Finance Act 2009 schedule 55 and schedule 56, legislation.gov.uk. Checked 29 Oct 2026.