How much CIS late filing costs
CIS penalties stack. They don't replace each other. Miss a return by 12 months and you're paying every tier, not just the last one.
| How late | Penalty | Running total |
|---|---|---|
| 1 day late | £100 | £100 |
| 2 months late | Another £200 | £300 |
| 6 months late | Another £200 or 5% of CIS deductions due (whichever is higher) | £500+ |
| 12 months late | Another £200 or more (up to 100% of deductions due in serious cases) | £700+ |
That's £700 minimum if you leave it a full year. And that's before HMRC adds interest on any deductions you owe. If you had significant CIS deductions due, the percentage-based penalties at 6 and 12 months push it much higher.
Nil returns get penalised too
Even if you had no deductions to report, the penalty still applies. The filing obligation exists regardless. A nil return filed late still costs you £100 on day one.
What to do right now
File the return. Even though it's late. The penalties are based on how late you are, so every day you wait makes it worse. Filing stops the clock.
Pay what you owe. If you've got CIS deductions outstanding, pay them. Interest is running on the amount due, and clearing the balance strengthens any appeal you might make.
Appeal if you have a reasonable excuse. HMRC uses those exact words. If something genuinely prevented you from filing on time, you can appeal the penalty within 30 days of receiving the notice. More on what qualifies below.
File first, appeal second
Don't wait until you've built your appeal case before filing. Get the return in now to stop further penalties stacking up. You can appeal afterwards. The appeal doesn't depend on the return being unfiled.
What counts as a "reasonable excuse"
HMRC is specific about this. A reasonable excuse is something unexpected that stopped you from meeting the deadline, where you filed as soon as you could once that reason was resolved.
Things HMRC accepts:
- Bereavement of a close family member
- Serious illness or hospitalisation
- Fire, flood, or natural disaster affecting your records or premises
- HMRC's own systems being down when you tried to file
- Postal delays that weren't your fault (if filing by post)
Things HMRC does not accept:
- "I forgot"
- "I didn't know I had to file"
- "My accountant didn't tell me" — you're still responsible, even if you pay someone else to handle it
- "I was too busy"
- "I didn't have the figures ready"
If you do have a genuine reasonable excuse, appeal online through your HMRC business tax account or by post. Include dates, evidence if you have it, and explain when the excuse ended and when you filed. Keep it factual.
How to stop this happening again
CIS returns are due monthly, by the 19th of each month (or the 22nd if you file online). That deadline doesn't move. Miss it once and you know how it feels. Here's how to make sure it doesn't happen twice.
- Set calendar reminders. Not for the 19th. For the 14th. Give yourself a few days' buffer so you're filing before the deadline, not on it.
- Use accounting software. Xero, QuickBooks, FreeAgent — they all handle CIS returns and will remind you when they're due. Some file directly to HMRC.
- Hand it to someone who does this for a living. An accountant or a back-office service that files your returns as part of the package. The cost of getting it handled is a fraction of a single penalty.
If CIS is just one of fifty admin tasks you're trying to juggle between jobs, the problem isn't the deadline. It's that you're running a business without a back office. That's fixable. For a proper breakdown of how CIS works, read the full CIS guide.