How to Vet a Subcontractor in Ontario Before You Hire

Hiring the wrong sub can cost you tens of thousands of dollars, blow up your timeline, and leave you holding the bag for someone else's mistakes. In Ontario's construction industry, the stakes are even higher — you can inherit liability for injuries, face WSIB penalties, and end up on the hook for rework that eats your margin alive.

The good news: most of this is avoidable. A solid vetting process takes maybe 30 minutes per sub, and it can save you from the kind of problems that sink projects and reputations.

Here's exactly how to do it.

Why Vetting Matters More Than You Think

A lot of GCs and contractors treat subcontractor vetting like a formality. They get a quote, it looks reasonable, they shake hands, and work starts. This is how problems begin.

Liability Transfers to You

In Ontario, if your sub doesn't have WSIB coverage and one of their workers gets hurt on your job site, you become the liable employer. That means you're on the hook for their injury costs, lost wages, and any WSIB penalties. This isn't a theoretical risk — it happens constantly.

The same principle applies to insurance. If your sub causes property damage or a third-party injury and they have no liability coverage, guess who the property owner or injured party comes after? You, the GC who hired them.

Quality and Rework Costs

An unvetted sub is a gamble on quality. If their work doesn't meet code or the client rejects it, you're paying for rework — often at a higher cost than the original scope, because now you're fixing problems under time pressure with a different crew.

Project Delays

Subs who disappear mid-project, can't pass inspections, or don't have the right licensing will stall your entire schedule. Every day of delay costs money — in carrying costs, in lost opportunity on your next job, and in damage to your reputation with the client.

The Vetting Checklist

Print this out. Save it. Use it every single time you bring on a new sub.

1. WSIB Clearance Certificate

This is non-negotiable. Before any work starts, get a current WSIB clearance certificate from every subcontractor.

A clearance certificate confirms two things:

The sub has an active WSIB account in good standing
They're current on their premium payments

Why it matters: Without this, you can be held liable as the "deemed employer" for any workplace injuries involving their workers. WSIB can — and will — come after you for unpaid premiums and injury costs.

How to verify: You can check a sub's WSIB status online through the WSIB's clearance certificate system at wsib.ca. You'll need their WSIB account number or legal business name. The system will tell you if they have an active account and if their premiums are up to date.

You can also request an Independent Operator Status letter if the sub claims they're an IO. This confirms they're registered as an independent operator and not being classified as your worker.

For a deeper breakdown of how WSIB works in construction, read our complete WSIB guide for Ontario trades.

2. Liability Insurance — $2M Minimum CGL

Ask for a Certificate of Insurance showing Commercial General Liability (CGL) coverage with a minimum of $2 million per occurrence. This is the industry standard in Ontario, and most serious GCs won't accept anything less.

What to look for on the certificate:

Named insured matches the business name on the contract
Policy is current — check the effective and expiry dates
Coverage amount is at least $2M per occurrence
Additional insured — request to be added as an additional insured on their policy for the duration of the project

Some trades carry higher limits — $5M is common for larger commercial projects. Match the insurance requirements to the project scope and the client's requirements.

Pro tip: Call the insurance company listed on the certificate to confirm the policy is active. Fake certificates exist. A two-minute phone call can save you from finding out at the worst possible time.

3. References and Past Work

Ask for at least three references from recent projects — within the last 12 months. Then actually call them. Most people skip this step, which is exactly why bad subs keep getting work.

Questions to ask references:

Did the sub complete the work on time?
Was the quality of work acceptable? Any callbacks or deficiencies?
Were there any safety incidents on site?
Did the sub communicate well and handle issues professionally?
Would you hire them again?

If a sub can't or won't provide references, that tells you everything you need to know.

Also look at their past work directly if possible. Photos are fine. A site visit to a completed project is better. You're checking for quality of finish, attention to detail, and whether their work looks like it was done by someone who takes pride in it.

4. Licensing and Certifications (Where Required)

Not every trade in Ontario requires a licence, but some absolutely do. If a sub is working in a licensed trade without proper credentials, you have a serious compliance problem.

Trades that require licensing or certification in Ontario:

Electrical: Must hold a valid licence from the Electrical Safety Authority (ESA). All electrical work must have an ESA permit and inspection.
Plumbing: Requires a plumber's licence. Journeyperson or master plumber certification is required to perform plumbing work.
Gas fitting: Must be licensed by the Technical Standards and Safety Authority (TSSA). Gas work without a TSSA-certified technician is illegal and dangerous.
HVAC (refrigeration): Requires an Ozone Depletion Prevention (ODP) certificate for handling refrigerants.

How to verify: Each licensing body maintains a public registry. You can search the ESA, TSSA, and other databases online to confirm a sub's credentials are current.

Don't assume the sub is licensed just because they say so. Verify it yourself.

5. HST Registration

If a subcontractor's annual revenue exceeds $30,000, they are required to register for and charge HST in Ontario. If a sub is doing significant volume but not charging HST, that's a problem — for them and potentially for you.

Ask for their HST number (also called a Business Number with an RT suffix). You can verify it through the CRA's GST/HST Registry online.

Why this matters to you: If the CRA determines your sub should have been charging HST and wasn't, there can be downstream complications with your own input tax credits. More practically, a sub who isn't registered when they should be is cutting corners on compliance — and if they're cutting corners there, where else are they doing it?

6. Written Contract and Scope of Work

Never start work on a handshake. Every subcontractor engagement should have a written contract that includes:

Detailed scope of work — what's included, what's not
Price — fixed price, unit price, or time and materials, clearly defined
Payment terms — milestones, holdback, timing
Timeline — start date, completion date, key milestones
Insurance and WSIB requirements — stated as conditions of the contract
Warranty — what the sub guarantees and for how long
Termination clause — how either party can end the agreement

A written contract protects both sides. If a sub pushes back on putting things in writing, that's a red flag.

Red Flags That Should Stop You Cold

Over the years, experienced GCs learn to spot warning signs early. Here are the ones that matter most:

No Insurance or Expired Coverage

If a sub says they "don't need insurance" or their certificate is expired and they promise to renew it "next week," walk away. Operating without insurance in construction is reckless, and it makes you liable by association.

Cash-Only Operations

A sub who wants to be paid entirely in cash, doesn't provide invoices, or doesn't have a business bank account is likely operating under the table. This creates problems for you with the CRA, makes it nearly impossible to enforce warranty claims, and suggests they're not running a legitimate operation.

Won't Provide References

Everyone starts somewhere, but an established sub who can't name a single past client they'd recommend you call is hiding something. New subs should at least be able to point to apprenticeship work, employer references, or portfolio evidence.

No Written Quote

A sub who gives you a verbal price and doesn't want to put anything on paper is setting up a situation where the scope and cost will shift once work is underway. Always get a detailed written quote that breaks down labour, materials, and any allowances.

Pressure to Skip Permits

If a sub suggests skipping permits or inspections to "save time" or "save money," this is a dealbreaker. Unpermitted work can result in stop-work orders, fines, forced demolition, and insurance claim denials. It can also make a property unsellable.

Unrealistically Low Pricing

If a quote comes in dramatically lower than everyone else's, ask yourself why. Sometimes it's because the sub is efficient and hungry for work. More often, it's because they're cutting corners on materials, not carrying proper insurance, or planning to hit you with change orders once work starts.

The Real Cost of Not Vetting

Skipping the vetting process isn't saving time — it's borrowing trouble. Here's what actually happens when it goes wrong:

WSIB Liability Transfer

If your unregistered sub's worker falls off a ladder on your site, WSIB will classify you as the employer. You'll be assessed for their premiums, the injury costs, and potential penalties. This can easily run $50,000 to $100,000+ depending on the severity of the injury. Your own WSIB premium rate will also increase, costing you more on every future project.

Rework and Deficiency Costs

Poor quality work that fails inspection or doesn't meet the client's expectations means tearing it out and doing it again. The rework typically costs 1.5 to 3 times the original price, because you're now paying for demolition, disposal, new materials, and a new crew — all while managing the schedule impact.

Project Delays and Liquidated Damages

On commercial projects, delays can trigger liquidated damages clauses — often $500 to $2,000+ per day. Even on residential projects, delays mean extended carrying costs, damaged client relationships, and lost opportunities on your next job.

Legal Costs

If things go really sideways — injury without insurance, significant property damage, contract disputes — you're looking at legal fees that start at $5,000 and can climb well into six figures. Most small contractors can't absorb this.

Reputation Damage

In Ontario's trades community, reputation is everything. One bad project caused by a bad sub can follow you for years. Clients talk. Other trades talk. Reputation is hard to build and easy to destroy.

How TradeBench Helps With Vetting

Building a reliable crew of subcontractors takes years of trial, error, and word-of-mouth. TradeBench accelerates that process through trust paths — a system that shows you how a potential sub connects back to people you already know and trust.

Instead of hiring blind, you can see that the electrician you're considering was referred by a plumber you've worked with for five years, who was brought in by a GC you trust completely. That chain of trust gives you confidence that a new sub is worth bringing onto your project.

It's not a replacement for the vetting checklist above — you should still verify insurance, WSIB, and licensing every time. But it's a powerful first filter that dramatically reduces the odds of hiring someone who'll cause problems.

If you're a GC or contractor in Ontario looking to build a more reliable network, sign up for TradeBench and start seeing who your trusted contacts can connect you to.

The Bottom Line

Vetting subcontractors isn't glamorous work. It's paperwork, phone calls, and due diligence. But it's the difference between a project that runs smoothly and one that blows up in your face.

Build the habit. Use the checklist. Verify everything. The 30 minutes you spend vetting a sub today can save you months of headaches and tens of thousands of dollars tomorrow.

This article is for informational purposes only and does not constitute legal, financial, or professional advice. Regulations and requirements change — always verify current rules with the relevant Ontario authorities, including the WSIB, ESA, TSSA, and CRA. Consult a licensed professional or legal advisor for advice specific to your situation.