If you work in construction as a subcontractor, HMRC's Construction Industry Scheme (CIS) probably takes 20% or 30% of your pay before you even see it. The good news? Most of that money comes back to you as a tax refund — if you know how to claim it. This guide explains everything from how CIS works to maximising your refund.
🏗️ Estimate Your CIS Tax Refund
Enter your gross CIS payments, deduction rate and expenses to see how much HMRC owes you back.
Estimate My Refund →What Is the Construction Industry Scheme?
The Construction Industry Scheme (CIS) is a set of HMRC rules that applies to construction work in the UK. Under CIS, contractors deduct money from payments to subcontractors and pass it directly to HMRC as advance tax payments.
CIS applies to most construction work including building, civil engineering, demolition, plastering, plumbing, electrical work, roofing, bricklaying, painting and decorating. It does not apply to architecture, surveying, carpet fitting, or delivery of materials only.
20% vs 30%: Registered vs Unregistered
The rate at which tax is deducted from your payments depends on whether you're registered with HMRC under CIS:
| Status | Deduction Rate | Net Payment |
|---|---|---|
| Registered CIS subcontractor | 20% | 80% of gross pay |
| Unregistered | 30% | 70% of gross pay |
| Gross status (rare) | 0% | 100% of gross pay |
If you're on 30% deductions, register for CIS immediately. It's free, takes minutes online, and instantly increases your take-home pay by 10 percentage points. On £40,000/year gross, that's an extra £4,000 in your pocket throughout the year.
How CIS Tax Refunds Work
At the end of the tax year, you file a Self Assessment tax return. HMRC calculates your actual tax liability based on:
- Your total CIS gross payments
- Minus your allowable business expenses
- Minus your Personal Allowance (£12,570)
- Income Tax at 20% on the remaining profit
- Plus Class 2 NIC (£3.45/week = £179.40/year if profit > £6,725)
- Plus Class 4 NIC (6% on profit between £12,570-£50,270; 2% above)
If the CIS deductions already taken (20% or 30% of gross) exceed your actual tax liability, HMRC refunds the difference. Most CIS subcontractors receive a refund because the flat deduction rate is higher than the effective tax rate after expenses.
Expenses You Can Claim
Claiming all allowable expenses is the single biggest factor in maximising your CIS refund. Common deductions include:
- Tools and equipment — drills, saws, ladders, scaffolding (purchased or hired)
- Protective clothing (PPE) — hard hats, boots, hi-vis vests, gloves
- Vehicle costs — Mileage at 45p/mile for first 10,000 miles, then 25p. Or actual fuel, insurance, servicing, MOT proportioned for business use
- Accommodation — Hotel/B&B costs when working away from home
- Phone — Business proportion of mobile phone bills
- Trade subscriptions — Membership fees for professional bodies
- Public liability insurance
- Accountancy fees
- Training — Courses directly related to your trade (CSCS cards, NVQs, etc.)
Keep all receipts. HMRC can request proof of any expense for up to 5 years after the tax return deadline.
How to Calculate Your Refund
Here's a worked example for a CIS bricklayer:
| Item | Amount |
|---|---|
| CIS gross payments | £45,000 |
| Less: Tools, PPE, mileage | -£4,500 |
| Less: Phone, insurance, subscriptions | -£1,200 |
| Net taxable profit | £39,300 |
| Less: Personal Allowance | -£12,570 |
| Taxable income | £26,730 |
| Income Tax @ 20% | £5,346 |
| Class 2 NIC | £179 |
| Class 4 NIC (6% of £26,730) | £1,604 |
| Total tax liability | £7,129 |
| CIS already deducted (20% of £45k) | £9,000 |
| ESTIMATED REFUND | £1,871 |
📊 Calculate Your Personal CIS Refund
Use our free calculator to estimate your exact refund based on your CIS payments and expenses.
Calculate My Refund →How to File Your Self Assessment
To claim your CIS refund, you must file a Self Assessment tax return:
- Register for Self Assessment by 5 October following the tax year end at gov.uk
- Gather your records — CIS statements from contractors, all expense receipts, bank statements
- File online by 31 January — go to HMRC's Self Assessment portal
- Complete the CIS section — enter total CIS deductions from your statements
- Claim expenses — enter all allowable business expenses
- Submit and wait — HMRC typically processes refunds within 4-8 weeks
When Will You Get Your Refund?
Online Self Assessment submissions are processed faster than paper returns:
| When you file | Typical refund timeline |
|---|---|
| April-June (early) | 4-6 weeks |
| July-December | 6-8 weeks |
| January (deadline rush) | 8-12 weeks |
Ensure your bank details are up to date with HMRC. You can check your refund status through your HMRC Personal Tax Account.
Frequently Asked Questions
What is the Construction Industry Scheme (CIS)?
How is my CIS tax refund calculated?
What records do I need to keep for my CIS tax return?
What happens if I don't file a Self Assessment as a CIS subcontractor?
Do I need to register for CIS?
🏗️ Ready to See Your Refund?
Our CIS Tax Refund Estimator calculates your exact refund in seconds. No signup required.
Estimate My CIS Refund →