How cis deduction works
Before paying a subcontractor, a contractor verifies their status with HMRC to confirm the correct deduction rate applies before the very first payment even goes out. The deduction is calculated on the labour element of the invoice only, materials are usually excluded entirely from the calculation, and the net amount left over is what the subcontractor actually receives into their bank account.
Each month, the contractor reports all CIS payments and deductions to HMRC and pays over the amounts withheld from every subcontractor paid that particular month. Subcontractors use their deduction statements as evidence of tax already paid when they complete their own self assessment return later, so accurate monthly records matter considerably to both sides of the working arrangement.
Example
A building contractor pays a registered subcontractor £2,000 for labour plus £500 for materials on a single invoice. Materials are excluded from the deduction, so CIS applies only to the £2,000 labour portion at the registered rate of 20 per cent, £400. The subcontractor receives £2,100 net (£2,000 minus £400, plus the £500 materials), and the contractor pays the £400 over to HMRC as part of that month's CIS return.
CIS Deduction in QuickBooks Online vs Xero
QuickBooks Online has a CIS feature that calculates deductions automatically once a subcontractor is marked as CIS-registered and produces monthly CIS returns ready for submission to HMRC. Xero includes CIS contractor tracking that applies the correct rate to labour and materials separately and generates the figures needed for the monthly return each time.
Common mistakes
- A subcontractor's verification status is not checked before the first payment, so the wrong deduction rate gets applied by mistake.
- Materials are not separated from labour on an invoice, so CIS is deducted from the full amount instead of only the labour portion as required.
- Monthly CIS returns are filed late or with incomplete deduction statements, leaving subcontractors without the records they need for their own self assessment return.
Why it matters
CIS deductions affect how much cash a subcontractor actually receives and what a contractor must report and pay to HMRC each month without exception. Getting the rate or the labour-materials split wrong either shortchanges the subcontractor or underpays HMRC, both of which create disputes and compliance risk. For contractors and subcontractors in UK construction, accurate CIS handling protects cash flow on both sides of the payment and keeps monthly HMRC filings correct.
Related terms
How LedgerBPO handles cis deduction
We verify subcontractor status, apply the correct CIS rate to each invoice and keep monthly CIS records reconciled and ready for submission. You or your accountant reviews and files the monthly return and issues deduction statements to subcontractors on time.