Overlapping duties, the “3 Cs”, and building health & safety into contracts
When you engage a contractor, you don't hand over your health and safety duties — you share them. Under the HSWA, contractors and their workers count as your workers, and every business with an overlapping duty must consult, cooperate and coordinate. You cannot contract out of your duties.
Both of you. Under the HSWA, the contractors and subcontractors carrying out work for you — and their employees — are classed as your workers, so you keep a health and safety duty to them.
Engaging a contractor does not move your duty across to them. The contracting business (often called the client or principal) and the contractor each have duties, and where those duties cover the same work, they overlap. The contractor also has its own duties to its workers. The result is shared responsibility, not a clean handover.
When more than one business has a health and safety duty for the same matter, those duties overlap. Section 34 of the HSWA requires every business with overlapping duties to consult, cooperate and coordinate activities, so far as is reasonably practicable.
Overlapping duties happen in a shared workplace (such as a building site) and along a contracting chain (where contractors and subcontractors provide services to a head contractor or client). The point of the “3 Cs” is to make sure everyone has a shared understanding of the risks, who is affected, and how the risks will be controlled — so there are no gaps and no duplicated effort. The size of a business does not automatically determine its influence; every business in the chain must work together, regardless of size.
A business cannot transfer, contract out of, or push its health and safety duties onto someone else in the contracting chain.
You can agree who will do what — in fact, sensible agreements about who manages which risk are encouraged — but even then, each business remains legally responsible for meeting its own duties. A clause that simply says “the contractor is responsible for all health and safety” does not remove your duty as the contracting business. The law looks at who has influence and control over the work, not at what the paperwork tries to say.
Manage contractor health and safety across the whole life of the contract — not just at the signing.
| Stage | What you do |
|---|---|
| 1. Plan | Define the work and identify its health and safety risks before you go to market. |
| 2. Prequalify & select | Check the contractor has a working health and safety system and the competence for the job (often via SiteWise, PreQual or Totika). |
| 3. Contract | Set clear health and safety expectations and responsibilities in the agreement. |
| 4. Induct & coordinate | Induct contractors to your site and agree how overlapping duties will be managed (the 3 Cs). |
| 5. Monitor | Check that health and safety is actually being managed while the work happens. |
| 6. Review | Review performance after the work to improve how you manage the next contract. |
Based on WorkSafe New Zealand guidance on working with other businesses and managing risk through the contracting chain.
Prequalification is how contracting businesses verify a contractor's health and safety system before awarding work — and it is how contractors prove they are a safe pair of hands.
Schemes such as SiteWise, PreQual and Totika give a recognised, independent check of a contractor's health and safety capability. For the contracting business, prequalification is a practical way to meet the “select a competent contractor” part of your duties; for the contractor, a strong rating wins work. See our full guide to SiteWise, PreQual & Totika for how the schemes work and how to pass.
Get a system that handles contractor records, inductions and prequalification evidence. Book a demo and we'll show you how it works — free 30-day trial included.
Both the contracting business and the contractor. Under the HSWA, contractors and subcontractors carrying out work for you are classed as your workers, so you keep a duty to them. Where your duties and theirs cover the same work, they overlap and are shared.
Contractors do have their own duties, but you cannot contract out of, or transfer, your duties to them. You can agree who manages which risk, but each business remains legally responsible for meeting its own health and safety duties.
It is the duty under section 34 of the HSWA for businesses that share overlapping duties to work together, so far as is reasonably practicable — sharing information about the risks, agreeing who controls what, and avoiding gaps or duplication. It is often called the “3 Cs”.
Yes. Contractors, their subcontractors and their employees who carry out work for your business are classed as your workers under the HSWA, which is why you hold a health and safety duty towards them.
Prequalification is not a legal requirement by name, but checking that a contractor is competent and has a working health and safety system is part of meeting your duties — and many clients now require SiteWise, PreQual or Totika before they will award work.
