CIS for contractors and subcontractors explained

What does CIS cover?

CIS applies to payments for construction operations within its scope. A business can be a contractor, a subcontractor, or both. For example, a building firm might receive payments from a principal contractor while paying another business for plastering. Each relationship needs its own assessment; receiving CIS deductions does not remove obligations when paying others.

Start by checking whether the work and the paying business fall within the scheme. Do not assume every invoice connected with a building project is covered. The GOV.UK CIS guide explains construction operations, exclusions and businesses outside construction that may nevertheless have contractor duties. Separate construction payments from employee wages in your records from the outset.

Why check employment status before applying CIS?

CIS registration does not establish self-employment. Before treating someone as a subcontractor, assess the actual working arrangement for tax purposes. A written agreement describing someone as self-employed is not decisive if the practical relationship points elsewhere.

Consider the engagement as a whole, including control, personal service, substitution and financial risk. Record the facts supporting the decision and revisit it when arrangements change. If the individual should be treated as an employee for tax purposes, operate PAYE rather than using CIS as an alternative.

The contractor's monthly return includes a declaration that the subcontractors listed are not employees. Resolve uncertainty before payment and filing, rather than relying on the subcontractor's preference. Keep the evidence with the engagement record, not just in a manager's inbox.

How are verification and deduction rates linked?

Obtain the subcontractor's correct legal or trading name, Unique Taxpayer Reference and other details required for their business type. Follow HMRC's verification rules before payment where verification is required, and retain the result and reference. Changed business details can mean an earlier result no longer fits the payee.

The rates are 20% for registered subcontractors, 30% where the subcontractor is unregistered or cannot be verified, and 0% where HMRC confirms gross payment status. Do not accept an invoice instruction as authority to change the rate. Apply HMRC's instructions and subsequent notifications. Gross payment status removes the deduction, not the reporting duty.

How do materials affect the calculation?

Start with the invoice total and remove VAT and permitted costs before applying the CIS percentage. GOV.UK identifies materials paid for directly by the subcontractor, consumable stores, qualifying plant hire, manufacturing or prefabrication costs, and fuel used other than for travelling.

The materials exclusion concerns direct cost, not an arbitrary materials percentage or a marked-up selling price. Ask for receipts or supporting evidence. Where evidence is unavailable, GOV.UK says to estimate the materials cost; retain a reasonable explanation of the estimate instead of accepting every invoice allocation without review.

Assume an invoice contains £1,000 labour and £200 directly purchased materials, with no VAT or other exclusions. At 20%, the deduction is £200 and the payment is £1,000. It is not a £240 deduction, because supported materials are excluded. If VAT applies, establish its treatment separately, including any domestic reverse charge question.

What belongs in the monthly return and statements?

Build the return from payments actually made in the relevant tax month, not simply invoices received. Reconcile subcontractor identities, payment totals, materials and deductions against the payment ledger. Include reportable gross-status payments even though no deduction was taken.

Submit through HMRC's CIS service or suitable software. If no subcontractors were paid, follow the nil-return or inactivity procedure rather than assuming silence closes the obligation. Check the current filing deadline using the linked guidance and record evidence of acceptance.

Where deductions are made, give each subcontractor a payment and deduction statement within the required timescale. It should agree with the payment record and return. Check official statement timing and pay deductions to HMRC under the applicable payment rules. Data filing and payment are separate actions.

Which checks prevent avoidable mistakes?

Subcontractors should compare statements with bank receipts and invoices, then resolve discrepancies promptly. Deductions generally count towards their eventual tax position; the method of claiming credit depends on business structure. Limited companies and sole traders do not necessarily recover deductions through the same process.

Outsourcing administration does not transfer legal obligations. Contractors remain responsible for CIS duties, and employers remain legally responsible for associated PAYE obligations. Agree who approves records, submits returns, issues statements and settles the liability. A rejected return needs action even if your payment spreadsheet was correct.

• Retain status decisions, verification results and materials evidence.
• Match deductions, statements, returns and payments to HMRC.
• Investigate changed legal identities before the next payment.
• Keep employee PAYE and subcontractor CIS records distinct.