Missed the Self Assessment deadline? What to do, step by step
If you've missed 31 January, don't panic, but don't wait. Penalties and interest grow over time, so the quicker you act, the less it costs.
Checked against GOV.UK on 23 October 2026. General information for sole traders in England, Wales and Northern Ireland, not tax advice. Scottish Income Tax rates are different.
Five steps, in order
- File now. The £100 penalty has already applied, but daily penalties start after 3 months. If you're missing figures, use sensible estimates and correct them later.
- Pay what you can. Penalties and interest are worked out on what's unpaid. See how to pay.
- Set up a payment plan for the rest. Online, usually if you owe £30,000 or less, within 60 days of the deadline. See Time to Pay.
- Appeal if you had a reasonable excuse, usually within 30 days. See how to appeal.
- Never registered? Register now. See registering.
What it costs if you leave it
| Filed this late | Filing penalties |
|---|---|
| Up to 3 months | £100 |
| 3 to 6 months | £100 + £10 a day (up to £900) |
| 6 months | Plus 5% of tax due or £300, whichever is greater |
| 12 months | Plus another 5% or £300 |
Late payment penalties (5% at 30 days, 6 months and 12 months) and interest come on top. See late filing penalties.
If you're owed a refund
CIS subbies who are owed money still get the £100 penalty, but there's nothing to pay late. Filing quickly gets your refund moving. See CIS refunds.
Check what you owe with the January tax bill calculator.
This guide is part of our Self Assessment guides for the self-employed.
Free: The UK Contractor's Cheat Sheet 2026/27
CIS rates, overtime maths, tax dates, mileage, VAT and late payment, on 2 pages. Keep it on your phone or print it for the van.
Frequently asked questions
What happens if I miss the deadline?
A £100 penalty, then more the longer it's late, plus late payment penalties and interest on unpaid tax.
Should I file even if I can't pay?
Yes. Filing stops the filing penalties growing, and you need a filed return to set up a plan online.
Can I still get a CIS refund if I file late?
Yes, but you'll get the £100 penalty and the refund comes later.
Sources
- Self Assessment tax returns: penalties – GOV.UK
- Estimate your penalty for late Self Assessment tax returns and payments – GOV.UK
- If you cannot pay your tax bill on time – GOV.UK
- Disagree with a tax decision or penalty – GOV.UK
- Self Assessment tax returns: sending a return – GOV.UK
This guide is general information, not legal, tax or financial advice. Rules and rates change, so check the linked GOV.UK pages for the current position.