The Construction Industry Scheme (CIS) is designed to regulate how tax is deducted from payments made to subcontractors in the UK’s construction sector. If you’re a contractor, it’s your legal obligation to submit a CIS return every month to HMRC, even if you haven’t paid any subcontractors in that period. Missing a deadline or filing incorrectly can lead to costly penalties, so knowing exactly how to file is essential.
In this guide, we’ll walk you through how to submit a CIS return step-by-step, the information you’ll need, how to avoid mistakes, and what to do if you need to make corrections.
Understanding CIS and CIS Returns
The Construction Industry Scheme requires contractors to deduct money from a subcontractor’s payments and pass it to HMRC as advance tax towards their income tax and National Insurance.
A CIS return is a monthly report detailing:
- All payments made to subcontractors in the tax month
- The CIS deductions applied
- Verification status of each subcontractor
- Subcontractors with gross payment status (0% deduction)
Even if no payments were made, you must still file with HMRC to declare this.
Want to know more about CIS Returns? Read our detailed blog on What Is a CIS Return.
Monthly CIS Return Deadlines
The CIS monthly return must be submitted to HMRC by the 19th of each month, covering the previous tax month (which runs from the 6th to the 5th).
Example: If your tax month ends on 5th June, your return is due by 19th June.
Step-by-Step: How to File a CIS Return
1. Register for CIS
Before you can file monthly CIS returns, you must register for the Construction Industry Scheme with HMRC. This applies to all contractors, regardless of business size.
2. Verify Your Subcontractors
Before paying subcontractors, you must verify their details with HMRC to confirm the correct deduction rate:
- 20%: registered subcontractors
- 30%: unregistered subcontractors
- 0%: gross payment status
3. Keep Accurate Records
You must maintain detailed CIS records for each monthly return, including:
- Subcontractor’s full name and UTR
- Payment amounts
- Deduction amounts
- Verification reference number
4. Calculate CIS Deductions
Contractors must calculate CIS deductions accurately based on the subcontractor’s status. Use accounting software like CloudCo Books or HMRC’s online calculator for accuracy.
5. Submit Your CIS Monthly Return
You can submit CIS returns:
- Through HMRC’s online service
- Using commercial CIS software (e.g., CloudCo Books)
- Via your accountant or CIS return assistant
Information You’ll Need to File
To file a CIS return, you’ll need:
- Contractor’s UTR and Accounts Office reference
- Subcontractor’s UTR and verification status
- Details of payments and deductions for the month
- Statement confirming subcontractor’s employment status
Filing Methods
| Method | Advantages | Disadvantages |
| HMRC Online Service | Free, direct filing | Manual entry, no automation |
| Commercial CIS Software | Automates verification, filing, and record-keeping | Subscription cost |
| Accountant/CIS Return Assistant | Handles everything for you | Service fees |
Sending Statements to Subcontractors
Contractors must send statements to subcontractors within 14 days of the end of each tax month, showing:
- Total payments
- Total deductions
- Verification number
This helps subcontractors with their own self-assessment tax returns.
Penalties for Missing the Deadline
Failing to submit your return on time can result in:
| Time Late | Penalty |
| 1 day late | £100 |
| 2 months late | £200 |
| 6 months late | £300 or 5% of deductions |
| 12 months late | £300 or up to 100% of deductions |
Correcting or Changing a CIS Return
If you make an error after submission, you can correct or change your CIS return through HMRC’s online service or your CIS software. Always act quickly to avoid further penalties.
What If You Haven’t Paid Any Subcontractors?
If you’ve made no payments to subcontractors in a month, you must notify HMRC that no return is due. Failure to do so can still trigger penalties.
Staying Compliant Year-Round
To stay compliant:
- Keep monthly CIS records up to date
- Verify subcontractors before each payment
- Use software or professional services to avoid missed deadlines
- Review returns before submission
Why Choose CloudCo Books for CIS Return Submission?
Submitting a CIS monthly return to HMRC isn’t just about ticking a box; it’s about making sure every detail is accurate, every subcontractor is verified, and every deadline is met. That’s where CloudCo Books steps in.
We specialise in helping contractors navigate the Construction Industry Scheme with ease. From verifying subcontractors and calculating CIS deductions to filing your return with HMRC on time, we handle the entire process so you can focus on running your business.
Our team of experienced CIS return assistants understands the regulations inside out, meaning you can avoid costly penalties and maintain full compliance. We ensure your records are complete, your statements are sent promptly to subcontractors, and if you’ve overpaid, we help you claim your CIS refund without delays.
When you choose CloudCo Books, you’re not just outsourcing a task; you’re gaining a trusted partner who makes CIS return submission smooth, accurate, and stress-free.
Final Thoughts
Submitting a CIS return is a monthly responsibility for contractors under the Construction Industry Scheme. By keeping accurate records, verifying subcontractors, calculating deductions correctly, and filing returns on time with HMRC, you can avoid penalties and maintain a smooth operation.
Whether you use CloudCo Books, HMRC’s online service, or a CIS return assistant, the key is to stay organised and proactive, because the deadline comes around every month.