CIS subcontractor tax calculator 2026/27
Estimate sole-trader tax and National Insurance, compare CIS deductions already taken and see a possible refund or balance due.
How the CIS subcontractor estimate works
The CIS estimate removes VAT and qualifying materials from the entered deduction base, compares CIS already deducted with estimated sole-trader Income Tax and Class 4 NI, and shows a possible balance or refund.
Rules checked
Read the checking method
What the result includes
- 0%, 20% and 30% CIS deduction rates
- Taxable profit after materials and other allowable expenses
- CIS credits compared with estimated annual liability
What to have ready
- Payment and deduction statements from contractors
- Invoices split between labour, materials and VAT
- Receipts for other allowable business costs
Questions about CIS subcontractor
Is CIS the subcontractor’s final tax?
No. CIS deductions are credits toward the final position. Profit, other income, National Insurance and allowable expenses determine the eventual bill or refund.
Are materials deducted twice?
They should not be. Qualifying materials reduce the contractor’s CIS deduction base and also form part of the subcontractor’s business-cost calculation.
About this estimate
CIS deductions are payments on account, not the final tax bill. VAT, materials, employment status, losses and allowable expenses must be supported by your records.