CIS Tax Calculator
Under the Construction Industry Scheme, contractors deduct tax from subcontractors' labour and pay it to HMRC. Many subcontractors have more deducted than they owe and can claim a refund through Self Assessment.
Tax year 2026/27 · Estimates, not personal tax advice
Estimated refund
£1,908.20
| CIS deducted | £8,000.00 |
| Taxable profit | £36,000.00 |
| Income Tax due | £4,686.00 |
| Class 4 NI due | £1,405.80 |
| Refund | £1,908.20 |
Rates and rules used
Tax year 2026/27Default year 2026/27 (6 April to 5 April). 2025/26 and 2024/25 figures are kept for comparison where the calculator offers a year choice.
- Construction Industry Scheme deduction rates2026/27GOV.UK: What is the Construction Industry Scheme (opens in new tab)
- Income Tax bands, rates and Personal Allowance2026/27GOV.UK: Income Tax rates and allowances (opens in new tab)
- Class 2 and Class 4 National Insurance2026/27GOV.UK: Self-employed National Insurance rates (opens in new tab)
Independent site, not affiliated with HMRC. Always check GOV.UK for the latest figures.
How this calculation works
- 01Deduct CIS at your status rate from labour (not materials).
- 02Work out profit after expenses.
- 03Calculate Income Tax and Class 4 NI on that profit.
- 04Compare with CIS already deducted to estimate a refund or balance.
Real payroll can differ because tax and NI are worked out per pay period, and your tax code may include adjustments HMRC hasn't told you about. See our methodology.
Materials aren't taxed
Deductions apply to labour only. If your invoices separate out materials, the contractor should deduct CIS from the labour element alone.
Understanding your cis tax calculator result
CIS deductions are advance payments towards the subcontractor's eventual tax bill. The estimate compares tax withheld from labour with the liability after expenses and allowances.
Checking a possible CIS refund
Scenario: Enter labour income, materials separately, allowable expenses and CIS already deducted from payment statements.
How to use the result: If deductions exceed the estimated final liability, the difference indicates a possible refund. The actual claim depends on complete records and the Self Assessment return.
Details to check before relying on the estimate
- Do not include qualifying materials in the deduction base.
- Reconcile every contractor statement before filing.
- A 30% deduction can indicate that registration details need checking.
Putting the estimate into perspective
Keep the payment statements supporting deductions alongside your income and expense records. An estimated refund is a reconciliation aid, not evidence that a repayment has been agreed.
Frequently asked questions
Why am I due a CIS refund?
The 20% deduction ignores your Personal Allowance and business expenses. Once those are accounted for on your tax return, many subcontractors have overpaid.
Check it on GOV.UK: What is the Construction Industry Scheme (opens GOV.UK in a new tab)
What is the CIS deduction rate?
Contractors deduct tax from payments to subcontractors at a rate set by whether you are registered with HMRC under CIS. Registered rates are lower than unregistered rates; check GOV.UK for the current percentages.
Check it on GOV.UK: What is the Construction Industry Scheme (opens GOV.UK in a new tab)
Can I reclaim CIS deductions?
Yes. The tax deducted counts as a payment towards your Self Assessment bill, and any excess is refunded once HMRC has processed your return.
Check it on GOV.UK: What is the Construction Industry Scheme (opens GOV.UK in a new tab)
Related calculators
- Self Employed Tax Calculator — Estimate the underlying tax and Class 4 NI on profit.
- Self Assessment Calculator — Bring CIS credits into the full return position.
Related guides
- CIS Tax Explained — How the Construction Industry Scheme works for subcontractors, the 20% and 30% rates, gross payment status and claiming refunds.
- Self Assessment Explained — Who needs to file a Self Assessment tax return, what goes on it, the deadlines for 2026/27 and the penalties for missing them.