CIS Contractors: How to Complete Your 2024/25 Self-Assessment Return
If you’re a self-employed worker in the construction industry and paid under the Construction Industry Scheme (CIS), then you’re probably familiar with the CIS self-assessment process. But with the 2024/25 tax year now behind us (ending on 5 April 2025), it’s time to make sure you file your return accurately—and take advantage of any tax reliefs you may be owed.
Whether you’re new to self-assessment or just need a refresher, here’s everything CIS contractors need to know for the 2024/25 return.
Why CIS Contractors Must File a Self-Assessment Return
Under CIS rules, contractors deduct 20% from your pay before you receive it. This is not the final amount of tax you owe—just a payment on account to HMRC. You’re still responsible for completing a CIS self-assessment return to declare your full income and claim any allowable expenses.
This is especially important because many CIS workers are due a tax refund. If your actual tax bill is lower than what’s already been deducted, HMRC will repay the difference once your return is processed.
Key Self-Assessment Dates for 2024/25
- 5 April 2025: End of the 2024/25 tax year
- 6 April 2025: First day you can file your return
- 31 October 2025: Deadline for paper returns
- 31 January 2026: Deadline for online filing and any tax payment due
Miss the deadline, and you could face penalties and interest charges—even if you’re owed a refund.
What You’ll Need to Complete the Return
Filing your return is much easier if you have the right information ready. You’ll typically need:
- Your Unique Taxpayer Reference (UTR) number
- Details of your income from CIS payment and deduction statements
- Records of any additional income (e.g. from other self-employed work)
- A list of allowable expenses (see below)
- Bank statements and receipts, especially for large purchases
- Any benefits or pension contributions relevant to the year
Using an accountant isn’t essential, but it can save time and help ensure accuracy—particularly if you’re claiming a lot of expenses.
What Expenses Can CIS Contractors Claim?
The more you can legitimately deduct as business expenses, the lower your taxable profit. HMRC allows you to claim for things like:
- Tools, equipment and protective clothing
- Travel and vehicle costs (excluding commuting to a regular site)
- Public liability insurance
- Mobile phone use (if it’s work-related)
- Accountancy or bookkeeping fees
- Training courses that improve existing skills
It’s important to keep receipts and records to back up your claims. HMRC may ask for evidence if your return is selected for review.
Common Mistakes to Avoid
CIS contractors can fall into several traps when filing their return:
- Forgetting to include all income, especially from smaller or one-off jobs
- Not claiming all allowable expenses, leading to overpaid tax
- Filing with incorrect UTR or personal details, delaying your refund
- Missing the deadline and triggering automatic penalties
- Failing to check if you’re due a refund and letting HMRC keep your money
Accuracy is key—if you’re not confident, speak to a qualified accountant or tax adviser familiar with the construction industry and CIS self-assessment.
How Long Does a CIS Tax Refund Take?
HMRC typically processes refunds within 7 to 21 working days, though it can be quicker if you file early. The sooner you submit your return after 6 April, the sooner your refund will arrive—especially if you file online.
Need Help with Your Return?
Self-assessment might feel like a hassle—but for many CIS contractors, it’s a chance to reclaim overpaid tax and stay in HMRC’s good books. The key is to stay organised, understand your entitlements, and act early.
If you’d like professional support with your 2024/25 CIS self-assessment, we recommend speaking to a tax specialist
Book a consultation with a tax specialist and make sure your return is accurate, compliant, and maximises your refund.
