Contractual chain duty (WHS)

Contractual chain duty is the Safe Work Australia principle that a PCBU’s WHS duties cannot be transferred to a subcontractor by sub-letting the work. Each PCBU in the contractual chain owes its own duty to its workers and to others affected by its work. The principle sits in the model WHS Act 2011 (and in similar form in the Victorian OHS Act 2004) and is the reason a builder engaging a subbie still owes a duty to that subbie’s workers, AND why the duty stretches further the deeper the chain runs.

The concept:

WHS law makes the PCBU’s duty non-delegable. The builder remains responsible for ensuring the work environment is safe AND that the subbie has the competence, plant, and method to do the work safely. The builder cannot satisfy that duty just by including a “subbie warrants their own safety” clause in the contract.

The chain:

Builder (head PCBU)
  → Subbie A (PCBU)
    → Subbie A's worker
  → Subbie B (PCBU)
    → Subbie B's worker
      → Apprentice in turn

At each level:

Each PCBU owes a duty to its own workers.
Each PCBU owes a duty to other persons affected by its work (including the workers of other PCBUs at the same workplace).
The duties run UP and DOWN the chain: builder owes a duty to subbie A’s workers; subbie A owes a duty to builder’s workers and to subbie B’s workers; and so on.

Practical implications for builders:

Action	What the duty requires
Engaging a subbie	Verify licence, insurance, competence; document the verification
Briefing the subbie on site hazards	Site-specific induction (not generic)
Confirming the subbie’s SWMS	For HRCW: SWMS in place, reviewed, signed
Confirming the subbie’s plant compliance	Plant registered if required, operator competent
Monitoring the subbie’s work	Not micromanage but spot-check for compliance
Hazard escalation	If subbie creates a hazard for others, builder must address

The builder is NOT expected to literally supervise every move the subbie makes. But the builder IS expected to set up systems (induction, SWMS check, sign-on, monitoring, escalation) that satisfy the duty.

Why the duty stretches deeper:

If the subbie sub-lets to a deeper subbie, the head builder’s duty extends to that deeper worker too. The case law and Safe Work Australia guidance is clear: contractual chain doesn’t dilute the duty.

Common builder errors:

“Subbie warrants its own safety” clause as the only WHS measure: doesn’t satisfy the duty.
No induction for the subbie’s worker: assumed the subbie inducted them; head builder still owes a duty.
No SWMS check: subbie does HRCW with no SWMS in place; head builder shares liability.
“Not my worker, not my problem”: this is exactly the position WHS law rejects.

Consequences:

In an incident, prosecutors can pursue multiple PCBUs in the contractual chain. A single subbie’s failure to manage a fall hazard can lead to a Cat 1 or Cat 2 prosecution against the builder, the subbie, and any deeper subbies involved.

For builders:

Verify every subbie at engagement: licence, insurance, white card, SWMS for HRCW.
Site-induct every worker entering the site, including subbie workers and deeper-chain workers.
Monitor compliance with SWMS for HRCW activities; document the monitoring.
Have a written escalation procedure for hazards the subbie creates that affect others.
Keep records: induction sign-on, SWMS review, hazard reports, near-miss reports.

Also known as: non-delegable WHS duty, chain-of-duty, duty not transferred by sub-letting.

Category: WHS / duties / contractual chain.

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