As a CIS subcontractor you are self-employed, so you are taxed on your profit — income after materials and expenses — plus Class 4 National Insurance. Your contractor deducts 20% (or 30% if unregistered) from your labour payments as an advance against that tax.
Because your personal allowance and expenses usually bring your real tax below the flat 20%, most subcontractors have had too much deducted and are owed a refund. This calculator estimates that refund from your figures.
From April 2026, CIS subcontractors over the income threshold keep digital records and file quarterly under Making Tax Digital, with deductions reconciled at the year-end Final Declaration.
Often yes. The 20% deducted by your contractor is usually more than your actual tax once your personal allowance and expenses are applied, so the difference comes back to you.
No. CIS deductions apply only to the labour element of your invoices; the cost of materials is excluded from the deduction.
From April 2026, CIS subcontractors over the threshold keep digital records, file quarterly, and confirm their CIS deductions at the year-end Final Declaration, where they're offset against the tax bill.
Loading the calculator…