IR35 vs CIS Explained for UK Construction And Labour Supply Chains
Understand the difference between IR35 and CIS, when each applies, and why construction labour supply chains often need to assess both.
IR35 and CIS are not the same rule under different names. IR35 is about employment-status tax risk where someone works through an intermediary such as a personal service company. CIS is a construction tax deduction scheme that affects how contractors pay subcontractors for construction operations.
Comparison Table
IR35 and CIS cover different compliance questions.
| Question | IR35 | CIS |
|---|---|---|
| What is it for? | Tests whether off-payroll work should be taxed like employment. | Sets deduction rules for payments to subcontractors in construction. |
| Who does it affect? | Clients, agencies, fee-payers, and workers operating through intermediaries. | Construction contractors and subcontractors. |
| Typical worker model | A worker supplying services through a personal service company or other intermediary. | A subcontractor being paid for construction operations. |
| Main decision | Would the worker look like an employee if engaged directly? | Should the payer verify and deduct under CIS, or pay gross? |
| Main outcome | PAYE and NIC obligations may sit with the fee-payer. | Payments may be made gross, or with 20% or 30% deductions depending on status and verification. |
Who This Is For
Construction businesses engaging labour through agencies, umbrella chains, or personal service companies.
Procurement, finance, and compliance teams trying to separate worker-status risk from payment-process risk.
Labour suppliers and MSPs that need one operating view of off-payroll and subcontractor controls.
When This Applies
Use IR35 analysis when services are supplied through an intermediary and the working arrangement may resemble employment.
Use CIS analysis when a contractor is paying a subcontractor for construction operations covered by the scheme.
In construction supply chains, both issues can appear around the same programme even though they answer different questions.
Detailed Explanation
The easiest way to avoid confusion is to ask two separate questions. First: is this person really operating as an independent business, or would they look like an employee if they were engaged directly? That is the IR35 question. Second: if this payment is for construction operations, does the payer need to verify the subcontractor and apply the Construction Industry Scheme? That is the CIS question.
IR35 sits inside the off-payroll working rules. It focuses on the status of the engagement, especially where a worker supplies services through a personal service company or similar intermediary. The practical consequence is that the worker may need to be taxed in a way that resembles employment for income tax and National Insurance purposes.
CIS does not ask the same status question. Instead, it governs how contractors pay subcontractors for construction work. Contractors may need to verify subcontractors with HMRC and then apply the correct payment treatment, including deductions where required.
That distinction matters because businesses sometimes treat CIS as if it were a full substitute for employment-status analysis. It is not. A deduction process cannot by itself answer whether an arrangement is genuinely outside employment-style tax treatment.
For operations teams, the risk is usually not a single wrong decision but fragmented workflow. One team onboards a supplier, another approves a rate, another processes timesheets, and finance receives an invoice without a consistent record of status checks, determinations, verification, or supporting documents.
The strongest compliance model separates the decision points but connects the evidence. You want a clear record of who assessed status, what evidence they relied on, whether the party was verified under CIS, what payment route was used, and what exceptions remain unresolved.
Frequently Asked Questions
Can IR35 and CIS both matter to the same business?
Yes. A construction business can have subcontractor payments that fall within CIS and separate off-payroll arrangements that need IR35 review. They are different compliance regimes, so one does not automatically answer the other.
Does CIS mean a worker is definitely self-employed?
No. CIS is a payment and deduction scheme. It does not by itself settle employment-status questions for every arrangement.
What is the operational mistake teams make most often?
They collapse status checks, supplier onboarding, and payment processing into one assumption. In practice, each step needs its own evidence and audit trail.
Where should a business start if it is unsure?
Start by mapping the engagement model: who contracts with whom, whether services are supplied through an intermediary, whether the work is construction work under CIS, and who is currently making payment decisions.
Official Sources
This guide is general information, not tax or legal advice. Check the current HMRC and GOV.UK guidance before relying on it for a live engagement.