CIS300 penalties and nil returns
A late monthly return costs £100 the day after the deadline, and more the longer it stays late.
The deadline
Each tax month runs from the 6th to the 5th of the next month. The CIS300 for that month must reach HMRC by the 19th.
Example: the return for 6 May to 5 June must reach HMRC by 19 June.
What a late return costs
| How late | Penalty |
|---|---|
| 1 day | £100 |
| 2 months | £200 |
| 6 months | £300 or 5% of the CIS deductions on the return, whichever is higher |
| 12 months | £300 or 5% of the CIS deductions on the return, whichever is higher |
| More than 12 months | You may get a further penalty of up to £3,000 or 100% of the CIS deductions on the return |
Nil returns: the rule changed on 6 April 2026
If you have paid subbies before, you must now send a return even in a month when you paid nobody. That is a nil return. The law says so from 6 April 2026.
You do not need one if you tell HMRC in advance that you will make no payments that month. GOV.UK calls this telling HMRC you have temporarily stopped using subcontractors.
How to appeal a penalty
- Appeal within 30 days of the date on the penalty notice.
- Online, through HMRC's CIS online service.
- Or by post: write to HMRC and quote your UTR and the payment reference on the notice.
- You cannot appeal over the phone.
Got something wrong on a return?
Use HMRC's CIS online service to correct it. If any entry comes to less than 0, put 0.
Paying the penalty
GOV.UK has a page for paying a CIS late filing penalty. It is listed under Sources.
See every return and payment date on the CIS deadlines calendar.
We checked this against the sources below on 31 Oct 2026. Rules change. You stay responsible for your own tax, so check anything unusual with your accountant or on gov.uk.
Sources
- GOV.UK, "What you must do as a CIS contractor: file your monthly returns" (gov.uk/what-you-must-do-as-a-cis-contractor/file-your-monthly-returns)
- The Income Tax (Construction Industry Scheme) (Amendment) Regulations 2026, SI 2026/289 (legislation.gov.uk/uksi/2026/289/made)
- GOV.UK, "Pay a Construction Industry Scheme (CIS) late filing penalty" (gov.uk/pay-construction-industry-scheme-cis-late-filing-penalty)
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