Most Ontario employers must register with the Workplace Safety and Insurance Board (WSIB) within 10 calendar days of hiring their first employee, pay premiums calculated as insurable earnings times a risk-based premium rate per $100 of payroll, and report qualifying workplace injuries within three business days. WSIB is a separate program from the Ontario Employer Health Tax (EHT) — this guide covers who must register, how premiums are calculated for 2026, the employer's injury-reporting obligations, and exactly how WSIB differs from EHT so the two are not confused when budgeting payroll costs.
Who must register for WSIB coverage
By law, most Ontario businesses must register with WSIB within 10 calendar days of hiring their first employee. Coverage is mandatory for most industries; some business activities fall outside compulsory coverage, though many of those employers can still register voluntarily for optional insurance. Construction is the notable exception in the other direction — coverage there is broader and can capture independent operators, sole proprietors and partners who would not need coverage in other industries.
Registering is free. In most cases a business gets its WSIB account number immediately after submitting its registration online, followed by a welcome email, a letter confirming the premium rate for its classified business activity, and a safety poster that must be displayed in the workplace. A business is also responsible for insuring anyone it employs — full-time, part-time, seasonal or temporary staff, certain domestic employees, and (in construction) unregistered individuals doing construction work.
Registering late, or not registering at all when coverage is mandatory, is not a minor paperwork gap. WSIB can respond with penalties, an investigation, provincial offences charges, or a bill for retroactive premiums covering the period the business should have been registered.
How WSIB premiums are calculated for 2026
WSIB premiums use a simple formula, applied per business activity:
Premium = insurable earnings × premium rate ÷ 100
Two variables drive that formula:
- Insurable earnings — the gross earnings (wages, salary, bonuses, most taxable benefits) the employer pays to covered workers during the reporting period, up to an annual maximum of $121,700 per worker for 2026. Earnings above that maximum are not included, and non-insurable amounts (such as EI top-ups) are excluded.
- Premium rate — set by the employer's classification, or rate group, which is based mainly on the business's NAICS activity code and reflects that group's shared claims-cost risk. A business with more than one NAICS code calculates and reports premiums separately for each one.
| Element | 2026 detail |
|---|---|
| Registration deadline | Within 10 calendar days of hiring the first employee |
| Premium formula | Insurable earnings × premium rate ÷ 100 |
| Annual insurable earnings maximum | $121,700 per worker |
| Average premium rate (all rate groups) | $1.23 per $100 of insurable payroll — the lowest average rate in more than 50 years |
| Injury reporting deadline | Within 3 business days of the reporting obligation starting |
The $1.23 per $100 figure is the average across all Ontario rate groups for 2026, not a flat rate every employer pays — a business's actual rate depends on its specific classification, since higher-risk industries carry higher rates and lower-risk industries carry lower ones. WSIB has cut the average rate by more than half over the past decade, and the 2026 reduction alone is projected to save Ontario businesses roughly $60 million compared with 2025.
Because premiums are risk-rated by classification rather than charged as a flat payroll percentage, two employers with identical payroll but different business activities — say, an office-based professional-services firm and a manufacturing operation — can owe very different WSIB premiums for the same insurable earnings.
Reporting a workplace injury or illness: the Form 7 obligation
An employer's reporting duty to WSIB is separate from, and faster than, the registration and premium cycle. An employer must report an injury or illness to WSIB within three business days of its reporting obligation starting. That obligation starts if the affected worker:
- needs treatment from a health professional beyond first aid, or
- is absent from work because of the injury or illness, or
- is paid less than their regular wage (fewer hours, reduced pay), or
- is on modified work at regular pay for more than seven calendar days following the incident.
If only first aid was needed, no time was missed, pay was unaffected, and modified work (if any) did not exceed seven calendar days, no report to WSIB is required. When the obligation does apply, the employer submits the Employer's Report of Injury/Illness (Form 7) and must give the affected worker a copy of it. Where the only trigger is modified work extending past seven calendar days at regular pay, Form 7 is due within three business days of the eighth calendar day of that modified work. Employers must also pay the worker a full day's wage on the day of the incident, and workplace fatalities or catastrophic accidents must be reported to WSIB by phone immediately, 24/7.
WSIB vs. the Ontario Employer Health Tax: two separate obligations
WSIB and the Ontario Employer Health Tax (EHT) are both employer costs tied to Ontario payroll, but they are unrelated programs and should never be treated as one line item:
| WSIB | Ontario EHT | |
|---|---|---|
| What it funds | Wage-loss and medical benefits for injured/ill workers | Ontario's health system generally |
| How the rate is set | By industry classification (rate group) and claims risk | By total Ontario payroll, with a $1,000,000 exemption for eligible employers |
| Basis of charge | Insurable earnings per worker, capped at $121,700 (2026) | Total Ontario remuneration, no per-worker cap |
| Registration/exemption trigger | Hiring the first employee (most industries) | Payroll crossing the $1,000,000 exemption, or exceeding $5,000,000 |
A business can owe WSIB premiums without owing any EHT (for example, a small employer under the EHT exemption but in a WSIB-covered industry), owe EHT without a meaningful WSIB rate exposure, or owe both. Model the EHT side specifically with the Ontario Employer Health Tax calculator, and see the Ontario EHT guide for the exemption and graduated-rate mechanics in full — that guide does not cover WSIB, and this one does not restate EHT's exemption math beyond the comparison above.
How RN Canada helps
RN Canada is an accounting and advisory firm headquartered in Edmonton, with a Vancouver office, serving Ontario and Toronto-area employers remotely from our head office. We help new Ontario employers confirm whether WSIB registration is mandatory for their classification, calculate insurable earnings and premiums correctly across NAICS codes, and keep EHT and WSIB obligations straight so neither is missed or double-counted when budgeting payroll. Our founder, Ozgur Duymaz, holds the CPA (Canada), ACCA (UK) and CMA (US) designations. Explore our bookkeeping & payroll service, model total payroll cost with the employer payroll cost calculator, and see how we serve businesses in Ontario and Toronto.
Frequently asked questions
Most do. By law, an Ontario business must register with the Workplace Safety and Insurance Board (WSIB) within 10 calendar days of hiring its first employee, unless its specific industry is exempt from mandatory coverage. Construction has its own, broader compulsory-coverage rules that can apply even to owners with no employees. Registering late, or not at all, can bring penalties, an investigation, provincial offences charges, or a bill for retroactive premiums.
Premium equals insurable earnings multiplied by the employer's premium rate, divided by 100. The rate is set by the employer's classification (rate group), based mainly on its NAICS business activity, and reflects that group's shared claims risk. For 2026, the average premium rate across all Ontario employers is $1.23 per $100 of insurable payroll, and insurable earnings per worker are capped at a $121,700 annual maximum.
Within three business days of the reporting obligation starting. That obligation begins if a worker needs treatment beyond first aid, is absent from work, is paid less than their regular wage, or is on modified work at regular pay for more than seven calendar days. The employer submits the Employer's Report of Injury/Illness (Form 7) and must give the worker a copy.
No. WSIB and the Ontario Employer Health Tax (EHT) are two entirely separate obligations that happen to both fall on employer payroll. WSIB is workplace-injury insurance: risk-rated premiums, set by industry classification, that fund wage-loss and medical benefits for injured workers. EHT is a payroll tax that funds Ontario's health system generally and has nothing to do with a specific employer's claims history. An employer can owe both, either, or neither, depending on its industry and payroll size.
Some business activities are not subject to compulsory WSIB coverage, though many of those employers can still opt in through optional insurance. Construction is treated differently: coverage there is broadly mandatory, including for many independent operators and sole proprietors who would be exempt in other industries. Employers unsure of their status should confirm their classification with WSIB directly rather than assume they are exempt.
Registering more than 10 calendar days after hiring the first employee can expose the business to penalties, a WSIB investigation, provincial offences charges, and retroactive premiums covering the unregistered period. WSIB treats registration as mandatory rather than optional for covered industries, so voluntary late registration does not erase the exposure for the gap before it — it only stops the gap from growing.