NAICS Codes and WSIB Classification: What Ontario Employers Need to Know

Every Ontario employer registered with WSIB is assigned a NAICS (North American Industry Classification System) code that determines their premium rate. This page explains how the classification system works, why it matters for your bottom line, and how to make sure you are in the right rate group.

What NAICS codes are and how WSIB uses them

The North American Industry Classification System is maintained by Statistics Canada, the U.S. Census Bureau, and Mexico's INEGI. It assigns every business a 6-digit code based on its primary economic activity. A residential framing contractor gets 238130. An electrician gets 238210. A trucking company gets 484110. WSIB uses these codes to group employers into rate groups — clusters of businesses with similar risk profiles and claims histories. Each rate group has a base premium rate expressed as dollars per $100 of insurable payroll. In 2025, rates range from as low as $0.28 per $100 (physicians) to as high as $6.78 per $100 (forestry and logging). The rate reflects the actual cost of injuries in that industry over the past several years — it is not arbitrary. Industries with frequent, severe injuries pay more because the claims cost more. The system is designed to be self-funding: premiums from all employers in a rate group collectively cover the cost of claims in that group.

Why your NAICS code matters for your WSIB premium

Your NAICS code is the starting point for your entire WSIB cost. Get classified in the wrong group and you could be overpaying by thousands of dollars a year — or underpaying and facing a retroactive adjustment when WSIB audits your account. Here is a concrete example: a contractor who does mostly finish carpentry (trim, cabinetry, millwork) should be in NAICS 238350 at $3.87 per $100. If WSIB classified them as a framing contractor (238130) at $5.21 per $100, they would overpay by $1.34 per $100 of payroll. On $400,000 of insurable payroll, that is $5,360 per year in unnecessary premiums. The reverse is also true — if a roofing contractor is misclassified as a siding contractor, they are underpaying, and WSIB can retroactively reassess premiums with interest. When you register with WSIB, describe your business activities honestly and specifically. Do not say "construction" — say "residential renovation, primarily kitchen and bathroom remodels, 70% finish carpentry and 30% tile work." WSIB assigns the code based on your primary activity. If your business changes over time, request a reclassification review.

Experience rating: how your claims history adjusts the base rate

The base rate from your rate group is not your final premium. WSIB applies experience rating adjustments that reward employers with fewer claims and penalize those with more. For larger employers (premiums over $25,000), the MAP (Merit Adjusted Premium) program compares your claims costs against the rate group average. If your claims are lower, you get a discount — potentially up to 50% off the base rate. If your claims are higher, you pay a surcharge. For smaller employers, the SCIP (Safety Check Insurance Plan) offers a simpler binary assessment: meet basic safety requirements and get a rebate. The practical effect is significant. Two framing contractors in the same rate group with the same payroll can have premiums that differ by tens of thousands of dollars based purely on their claims history. This is why workplace safety is not just a legal obligation — it is a direct financial advantage. Every lost-time injury increases your experience rating surcharge for years. A single serious fall claim on a small contractor's account can increase premiums by 30% or more for 3 to 5 years.

Mandatory vs optional coverage

Most industries in Ontario require mandatory WSIB registration. All of construction (NAICS 23), manufacturing (31-33), mining (21), transportation (48-49), retail (44-45), food service (72), and healthcare facilities (62) are mandatory. If you operate in these sectors and have employees, you must register with WSIB, report payroll, and pay premiums. Operating without coverage when it is mandatory is an offence under the Workplace Safety and Insurance Act — WSIB can retroactively assess premiums plus penalties. Some industries have optional coverage, primarily professional services (architects, engineers, consultants, lawyers, accountants) and certain financial services. Even in optional sectors, many employers choose to register because WSIB provides no-fault insurance: workers receive benefits without litigation, and employers are protected from negligence lawsuits. Independent operators — sole proprietors with no employees — can opt into WSIB coverage voluntarily. This is common in construction, where general contractors and principals require all subcontractors to provide WSIB clearance certificates regardless of the sub's employment status. Without coverage, the principal contractor inherits the liability for any workplace injury.

Construction trades: a closer look at the rates

Construction has the widest spread of premium rates of any sector because the risk varies enormously by trade. At the high end, roofing contractors (238160) pay $6.24 per $100 — working at height on sloped surfaces with hot materials produces frequent and severe injuries. Structural steel and ironworkers (238120) pay $5.87 per $100 for similar reasons: falls from structural steel are among the deadliest workplace incidents in Ontario. Concrete foundation contractors (238110) pay $5.34 per $100 — formwork collapses, reinforcing steel injuries, and concrete pump accidents drive the claims. At the lower end of construction, electricians (238210) pay $2.78 per $100. Electrical work is hazardous in its own way (electrocution, arc flash), but the injury frequency is lower than trades involving heavy physical labour at height. Plumbers and HVAC contractors (238220) pay $2.95 per $100. Painters (238320) pay $3.21 per $100. These rates reflect real data: the trades with lower rates genuinely have fewer and less costly claims on average. That said, every trade carries risk, and the rates do not mean one trade is "safe" — they mean the aggregate cost of injuries across all employers in that code is lower per dollar of payroll.

How to use this tool

Type your trade, job description, or NAICS code number into the search bar. The tool instantly filters all entries and shows matching NAICS codes with their WSIB rate group, base premium rate per $100, mandatory or optional coverage status, and common trade names that fall under each code. You can also browse by NAICS section using the filter pills — useful if you are not sure which code applies and want to scan all construction codes, for example. The rates shown are 2025 base rates before experience rating adjustments. Your actual premium will differ based on your MAP/SCIP adjustment, claims history, and insurable earnings. Use the print button to generate a PDF of your search results for your records or to share with your accountant. For your specific rate, contact WSIB at 1-800-387-0750 or log into your account at wsib.ca.

About NAICS Code Lookup

Free NAICS code lookup for Ontario employers. Search by trade or job description to find your WSIB rate group, premium rate per $100, and whether coverage is mandatory — construction, manufacturing, retail, trucking, and more.

How to use

  1. [object Object]
  2. [object Object]
  3. [object Object]
  4. [object Object]
  5. [object Object]
  6. [object Object]
  7. [object Object]

Examples

Residential roofing contractor
Search 'roofing' → match: NAICS 23816 / WSIB rate group construction trades, rate ~8.45 per $100. Mandatory Schedule 1 coverage. With $400,000 insurable payroll: premium = 400,000 × 8.45 ÷ 100 = $33,800 base, before NEER/MAP adjustments.
Bookkeeping office, 4 employees
Search 'professional services' → match: NAICS 54 / WSIB rate ~0.36 per $100. Schedule 1 but exempt unless opted in for some configurations. With $250,000 insurable payroll opted-in: premium = 250,000 × 0.36 ÷ 100 = $900 base.

Frequently asked questions

What is a NAICS class and how does it affect WSIB premiums?
NAICS — North American Industry Classification System — is the standard taxonomy Statistics Canada and WSIB use to group employers by predominant business activity. WSIB assigns each Schedule 1 employer to a single class based on the work the majority of its workers perform; the class determines the published premium rate per $100 of insurable earnings. Higher-injury industries (roofing 8.45, framing 9.12) pay much more than lower-risk classes (professional services 0.36). Classification also feeds the experience-rating programs (NEER for large employers, MAP for small) that adjust the base rate based on the employer's actual claim costs.
What's the difference between Schedule 1 and Schedule 2?
Schedule 1 employers — most Ontario private-sector industries — pay annual premiums into the WSIB collective pool, and the WSIB pays claims out of that pool. Schedule 2 employers (federal government, municipalities, public utilities, and some federally regulated industries like railways and airlines) self-insure: they reimburse WSIB the full cost of every claim filed by their workers, plus an administration fee. Schedule 2 employers do not pay premium rates — they pay actual claim costs. Most small business owners are Schedule 1 unless explicitly excluded.
What if my business does multiple activities?
WSIB classifies based on the predominant activity — the work that occupies more than 50% of payroll. A general contractor who also does some roofing falls under construction's general-contractor class, not roofing's higher rate. But if the secondary activity has materially different risk and a separately operated workforce, WSIB may assign multiple classes through the multi-rate program. Misclassification (declaring office payroll while workers are on roofs) is one of the WSIB's top audit triggers and can trigger retroactive reassessment plus penalties under WSIA s. 152.
How do I appeal my WSIB rate group classification?
An employer who disagrees with their assigned class can request a reassessment through the WSIB Employer Account Services. The request must include a description of business activities, payroll allocation by activity, work locations, and supporting documents (corporate structure, lease agreements, equipment lists). If the initial decision is unfavourable, the employer can appeal to the WSIB Appeals Services Division and then to the Workplace Safety and Insurance Appeals Tribunal (WSIAT). Reassessment can result in a lower (or higher) rate; the employer is responsible for ensuring records support the declared classification at every audit.
Is WSIB coverage mandatory for every Ontario employer?
Mandatory for most. WSIA s. 11 makes coverage compulsory for any employer in a Schedule 1 industry that employs at least one worker. Construction is universally mandatory under WSIA s. 12.2 — even sole proprietors and partners with no employees must register and pay premiums on their own labour earnings. Some industries are excluded from mandatory coverage (banks, insurance, financial services, professional services in some forms) but can opt in. Working without coverage when required carries fines up to $25,000 plus retroactive premium assessment with 12% compound interest under WSIA s. 158.
How are premium rates set each year?
WSIB's Rate Framework, in force since 2020, sets each class's annual rate based on the cumulative claim costs from that class's experience over the past 6 years, divided by total insurable payroll, with smoothing to limit year-over-year volatility. Within each class, individual employers' rates are adjusted up or down through experience-rating: NEER (the experience program for large employers, $25,000+ premium) and MAP (Merit Adjustment Premium, for smaller employers). Both can swing an employer's actual rate ±60% from the class average based on three-year claim history.
What's the difference between insurable earnings and gross payroll?
Insurable earnings under WSIA s. 25 are the gross wages paid to workers up to the annual maximum (2025: $112,500 per worker), excluding certain payments (severance, pension contributions, employer share of CPP/EI, certain bonuses). Gross payroll is the total — insurable earnings is the WSIB-relevant subset. Premium = insurable earnings × class rate ÷ 100. An employer paying $200,000 to a single worker in a 5.66 rate class pays premium on $112,500 (the cap), not $200,000 — capped premium = $6,367.50.

Part of ToolFluency’s library of free online tools for WSIB & OHSA. No account needed, no data leaves your device.

You might also need

💰WSIB Premium Calculator 🏗️Worker Classification Test 🚨Critical Injury Reporting 🩹First Aid Requirements