If you work in construction as a subcontractor, the contractor paying you must deduct CIS tax from the labour part of each invoice before it reaches you: 20% if you are registered for CIS, 30% if you are not, and 0% if you hold gross payment status. Materials you paid for are excluded from the deduction. Enter a typical monthly invoice below to see what lands in your account each month, what gets deducted over the year, and roughly how much of it comes back as a refund when your Self Assessment is filed.
The direct cost of materials you bought for the job. CIS is only deducted from the labour element, so materials come off before the rate is applied.
Your self-employed income minus all allowable expenses (tools, travel, materials, insurance). This drives the year-end tax comparison, not the CIS deduction itself.
CIS deductions are taken from turnover, but your actual tax is charged on profit after expenses. Because expenses are ignored at the point of deduction, most subcontractors overpay during the year and reclaim the difference through Self Assessment. This is an estimate: payments on account, other income, and Class 2 NIC are not modelled.