April 4, 2026 · Mainforce Team

CNESST and WSIB Coverage for Temporary Workers: What Clients Need to Verify

When a temporary worker is injured at your facility, two questions determine who pays: who is the worker's employer of record, and does that employer have active workers' compensation coverage?

If the answers are "the staffing agency" and "yes," the claim is processed through the agency's account. If the answer to either question is unclear or negative, you, the client company, may be held liable for the full cost of the claim. In Ontario, a single lost-time injury in a warehouse environment can easily run into the tens of thousands of dollars in WSIB claim costs, and severe injuries (crush injuries, falls from height) can cost far more.

This is not a theoretical risk. It is a recurring problem.

How Workers' Compensation Works With Temporary Staffing

Ontario (WSIB)

The Workplace Safety and Insurance Act, 1997, establishes that the "employer" is the entity that pays the worker's wages and controls the employment relationship. For temporary staffing, the staffing agency is the employer of record and must carry WSIB coverage.

In practice, responsibility is split. Workers' compensation obligations sit with the agency, while workplace safety obligations under Ontario's Occupational Health and Safety Act also apply to the client that controls the workplace:

The agency is responsible for: WSIB registration, premium payment, reporting obligations, and return-to-work obligations.
The client is responsible for: workplace safety, hazard identification, providing a safe work environment, and ensuring the agency worker receives the same safety training and protection as permanent employees.

If the agency stops paying its WSIB premiums, the Act allows the WSIB in some cases to hold the company that contracted the work liable for amounts the agency failed to pay. The rationale is straightforward: someone must pay, and you controlled the workplace where the work was done.

Quebec (CNESST)

The Act Respecting Industrial Accidents and Occupational Diseases operates on similar principles but with some key differences:

In Quebec, the "establishment" where the worker performs duties can be held jointly responsible for claims if the staffing agency's CNESST registration is not current.
Quebec has a more aggressive joint liability framework: the CNESST can and does pursue client companies when agencies default on premiums.
Quebec also requires that temporary workers receive workplace-specific health and safety training before starting work, and the client is responsible for providing it.

Other Provinces

British Columbia (WorkSafeBC), Alberta (WCB Alberta), Manitoba (WCB Manitoba), and other provinces follow similar frameworks with provincial variations. The common principle is: the staffing agency carries the coverage, but the client facility shares responsibility for workplace safety and may become liable if the agency's coverage is deficient.

The Verification Protocol

Before You Sign a Staffing Contract

Request and verify the following from any staffing agency before they place workers at your facility:

1. WSIB/CNESST Account Number

Get the actual account number. Do not accept "we have coverage" as an answer. Then verify it independently:

Ontario: Use WSIB's online employer clearance certificate system. You can verify whether the account is active and in good standing.
Quebec: Request a CNESST attestation of compliance (attestation de conformité). This document confirms the employer is registered and current on premiums.
BC: Request a WorkSafeBC clearance letter.

2. Clearance Certificate

A WSIB clearance certificate confirms the employer has no outstanding balances and their account is active. In Ontario, you can request that the staffing agency provide a clearance certificate or you can look it up online using their legal business name and WSIB account number.

This is not a one-time check. Clearance certificates have expiration dates (typically 90 days in Ontario). Request updated certificates quarterly.

3. Classification Verification

Since 2023, WSIB premiums have been set through a NAICS-based classification system combined with each employer's own claims history, replacing the older rate groups. Ask the agency how its business is classified and how that classification accounts for the warehouse or industrial work its employees perform at client sites.

Some agencies attempt to reduce premiums by reporting their operations under a lower-risk classification. If WSIB discovers this during an audit, the agency is reassessed, and while the reassessment is being processed, their coverage status may become uncertain. Verify that the agency's classification matches the type of work their employees perform at your site.

4. Insurance Certificate

In addition to WSIB/CNESST, request:

Commercial general liability insurance ($2M minimum, $5M recommended)
Certificate naming your company as additional insured
Confirmation the policy includes coverage for temporary workers placed at client sites

What Happens When Coverage Lapses

Here is a scenario that plays out more often than it should:

A staffing agency falls behind on WSIB premiums. WSIB issues a notice. The agency does not respond within the cure period. Coverage is suspended. The agency continues placing workers at client sites during the suspension period because stopping placements means stopping revenue.

A worker at Client X's warehouse is injured during the coverage lapse. The worker files a WSIB claim. WSIB discovers the agency's account was suspended. WSIB processes the claim (the worker is covered regardless; this is a fundamental principle of the system) and then works to recover what the agency owes, which can include looking to the client company that contracted the work.

For Client X, the result can be an unexpected bill, management time spent disputing it and legal fees, all for a worker who was never on its payroll.

This entire scenario is prevented by quarterly verification of the agency's clearance certificate.

Your Contractual Protections

Your staffing agreement should include:

Warranty of coverage: The agency warrants that it maintains active WSIB/CNESST coverage for all workers placed at your site, at all times.
Indemnification: The agency indemnifies you for any costs arising from a lapse in their workers' compensation coverage.
Notification obligation: The agency must notify you immediately if their coverage status changes for any reason.
Right to verify: You have the right to verify the agency's coverage status at any time, and the agency will cooperate with verification requests within 48 hours.
Termination trigger: A lapse in coverage constitutes grounds for immediate termination of the staffing agreement.

These contractual provisions do not replace verification: an indemnification clause is worthless if the agency goes bankrupt after a coverage lapse. But they establish the legal framework for recovery if a problem occurs.

The Daily Safety Obligation

Regardless of who carries the WSIB/CNESST coverage, you are responsible for providing a safe workplace. This means temporary workers must receive:

Site-specific safety orientation before starting work
Hazard-specific training for their assigned tasks
The same PPE and safety equipment as permanent workers
Inclusion in your joint health and safety committee processes
The right to refuse unsafe work without reprisal

Treating temporary workers as second-class citizens in your safety program is not only ethically wrong, it increases your liability exposure. A health and safety investigation into a temporary worker injury will examine whether the worker received adequate training and safety orientation. If they did not, your company can face orders, charges or fines under provincial health and safety law, regardless of the agency's coverage status.

Frequently asked questions

Who pays the WSIB claim if a temp worker is injured at my site?

Normally the staffing agency, as employer of record, carries the WSIB coverage and the claim goes through its account. If the agency's coverage has lapsed, the injured worker is still covered, but the client company can in some cases be held liable for amounts the agency failed to pay. That is why clients need to verify agency coverage regularly.

How do I check that a staffing agency's WSIB coverage is active?

Get the agency's actual WSIB account number and look up its clearance certificate through WSIB's online clearance certificate system, using the legal business name. Clearance certificates expire, so request an updated one every quarter instead of checking once at signing.

What document proves a Quebec staffing agency is current with CNESST?

Ask for a CNESST attestation of compliance (attestation de conformité), which confirms the agency is registered and up to date on its premiums. In Quebec, the client also has to make sure temporary workers get workplace-specific health and safety training before they start.

What should a staffing contract include to protect against coverage lapses?

Include a warranty of active WSIB or CNESST coverage, indemnification for costs from any lapse, an obligation to notify you right away of status changes, a right to verify coverage at any time, and a lapse as grounds for immediate termination. Those clauses help with recovery, but they do not replace regular verification.

If you are unsure about your current staffing agency's compliance status, or if you want to verify that your coverage is airtight, contact our team. Ask any agency, including us, for current WSIB and CNESST clearance certificates before work starts.

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