Self Assessment penalty calculator for the 2025/26 return

File your 2025/26 return online after 31 January 2027 and HMRC charges £100. From 1 May 2027 it can add £10 a day for up to 90 days (£900). Still not filed by 1 August 2027? A further 5% of the tax due or £300, whichever is greater, and the same again from 1 February 2028. Paying late is separate: 5% of the tax still unpaid at 30 days, 6 months and 12 months, plus interest at 7.75% a year (the rate on GOV.UK when we checked on 3 November 2026).

Written and reviewed by James Whitfield · Last reviewed 3 November 2026 · An estimate, not HMRC's figure or advice. HMRC has its own penalty estimator.

The penalty dates for the 2025/26 return

Late filing (online return)	Penalty
Filed on or after 1 February 2027	£100
Still not filed on 1 May 2027	£10 a day, up to 90 days (£900)
Still not filed on 1 August 2027	5% of the tax due or £300, whichever is greater
Still not filed on 1 February 2028	Another 5% or £300, whichever is greater

For a paper return the same steps run from the paper deadline: £100 from 1 November 2026, daily penalties from 1 February 2027, then 1 May 2027 and 1 November 2027. Missed the paper deadline? You can still file online by 31 January 2027 without a penalty.

Late payment (tax due 31 January 2027)	Penalty
Still unpaid on 3 March 2027 (after 30 days)	5% of the unpaid tax
Still unpaid on 3 August 2027 (6 months)	5% of what is still unpaid
Still unpaid on 3 February 2028 (12 months)	5% of what is still unpaid
Any amount paid after 31 January 2027	Interest from the day after, 7.75% a year from 9 January 2026

Dates from Finance Act 2009 Schedules 55 and 56: each period runs from the day after the deadline (for late payment, from the day after the 30 days). The daily penalties start on the date in HMRC's notice, which can't be earlier than 1 May 2027; we assume that date.

Worked examples

Filed 1 September 2027 with £2,000 of tax, paid on time. £100, plus 90 days of £10 (£900), plus £300 at 6 months because 5% of £2,000 is only £100: £1,300.00.
Filed 1 March 2028 with £10,000 of tax, paid on time. £100 + £900 + 5% of £10,000 at 6 months (£500) + another £500 at 12 months: £2,000.00.
Filed on time, £4,000 paid on 1 April 2027. 5% late payment penalty of £200.00, plus 60 days' interest at 7.75% (£50.96): £250.96.

What this calculator leaves out

Deliberately withheld returns. If HMRC decides information was deliberately withheld, the 12-month penalty can be higher than 5%.
Interest on penalties paid late, and part payments made at different dates. Enter the date the last of the tax was paid for a cautious figure.
Payment plans. HMRC's manual says no late payment penalty is charged if you agree a Time to Pay arrangement within 30 days of the due date and keep to it. See can't pay your Self Assessment bill.
A late notice to file. If you registered after 5 October 2026, HMRC gives you a filing deadline 3 months from the date of its letter or email, so the filing dates above don't apply. The tax is still due on 31 January 2027. See missed the 5 October deadline.
Making Tax Digital. GOV.UK says the current penalties apply to the 2025/26 return, even if you joined MTD from 6 April 2026.

Got a penalty you think is wrong, or you had a reasonable excuse? You usually have 30 days to appeal: see how to appeal a Self Assessment penalty.

Frequently asked questions

What is the penalty for filing my 2025/26 tax return late?

£100 if the online return arrives after 31 January 2027. From 1 May 2027 HMRC can add £10 a day for up to 90 days (£900). If it is still not filed by 1 August 2027 there is a further 5% of the tax due or £300, whichever is greater, and the same again from 1 February 2028.

Do I get a penalty if I owe no tax?

Yes. The £100 late filing penalty and the daily penalties apply even if there is no tax to pay. The 6-month and 12-month penalties are then £300 each, because £300 is greater than 5% of nothing.

When do late payment penalties start for the 31 January 2027 bill?

Tax for 2025/26 still unpaid 30 days after 31 January 2027 gets a 5% penalty, and 5% more of anything still unpaid 6 months and 12 months after the deadline. Interest is charged on top from the day after the deadline.

Are there penalties for paying a payment on account late?

No 5% penalties, but interest is charged on a late payment on account. If it is still unpaid, it becomes part of the next balancing payment, which does attract penalties.

Can a late payment penalty be avoided if I can't pay?

File on time and ask HMRC for a payment plan (Time to Pay). HMRC's manual says no late payment penalty is charged if you make proposals that lead to an acceptable arrangement within 30 days of the due date, and you keep to it. Interest still runs.

Do the new Making Tax Digital penalties apply to my 2025/26 return?

No. GOV.UK says the current penalties apply to the 2025/26 return due 31 January 2027, even if you joined Making Tax Digital from 6 April 2026.