Self-Assessment late-filing penalty
Map late-filing penalty trigger dates for a Self-Assessment tax return: £100 immediate, £10/day after 3 months, 5% / £300 at 6 months, another at 12 months.
Fill in your details and press Calculate.
How this is calculated
The calculator maps the late-filing penalty milestones for a Self-Assessment return (see the Schedule 55 penalty regime linked below). It takes the tax year you select, fixes the online filing deadline at 31 January following the end of that tax year, and then plots four trigger dates:
- Day 1 after the deadline: an immediate fixed £100 penalty — charged even if you owe no tax or are due a refund.
- 3 months late: daily £10 penalties begin, running for up to 90 days (maximum £900). The estimate counts the days between the 3-month point and your expected filing date, capped at 90.
- 6 months late: a further £300 or 5% of the tax due, whichever is greater.
- 12 months late: another £300 or 5% — rising to up to 100% of the tax in cases of deliberate withholding of information.
Enter your expected filing date and the tool adds up which bands you would fall into. Because it does not know your tax bill, the 6- and 12-month figures assume the £300 minimum — if 5% of your tax due is more than £300, the real penalty is higher than shown. All five dates come with an .ics download so the milestones sit in your calendar.
What this tool does not cover: the 31 October paper filing deadline (it assumes you file online), late-payment penalties (5% of unpaid tax at 30 days, 6 months and 12 months — a separate regime from late filing), and daily late-payment interest, which HMRC adds on top of everything. You can appeal a penalty if you have a "reasonable excuse" — serious illness, bereavement, or an HMRC systems failure, for example — but ignorance of the deadline is not accepted. If you no longer need to file at all, ask HMRC to withdraw the return notice: a withdrawn notice cancels the penalties with it.