WSIB registration for small business in Ontario: who, when, and how much

The short answer

Most Ontario businesses that hire an employee — including a family member — must register with the Workplace Safety and Insurance Board (WSIB) within 10 calendar days of that hire. Construction is a special case: compulsory coverage there extends well beyond employees to most sole proprietors, partners, and independent operators in the industry. Outside construction, business owners without employees aren't automatically covered but can opt in.

WSIB is Ontario's no-fault workplace insurance system: employers pay premiums, and in exchange injured workers get compensation without suing the employer. It runs parallel to payroll, not through it — which is exactly why it's easy to miss when you're focused on CRA remittances and forget there's a second regulator watching your first hire.

Who has to register, and when

The trigger is hiring your first employee — full-time, part-time, or a family member on payroll. Sub-contractors can also count, which is where a lot of businesses get caught out (more on that below). Once you're covered, registration is due within 10 calendar days of that first hire.

Outside construction, business owners themselves — sole proprietors, partners, executive officers — aren't automatically required to carry WSIB coverage on their own labour. If you want that protection anyway, WSIB offers optional insurance you can apply for.

Why construction is different

Construction carries expanded compulsory coverage that generally reaches sole proprietors, partners, and independent operators in the industry — not just people on someone else's payroll. If your business does any construction-related work, don't assume the "no employees, no registration" rule from other industries applies to you; it usually doesn't. This is one of the more common gaps we see in trades bookkeeping, and it's worth confirming your status directly with WSIB rather than guessing from what a similar business down the street does.

How premiums work

Once registered, WSIB premiums follow a simple formula: premium = insurable earnings × premium rate / 100. The rate is set per $100 of insurable earnings and depends on your business classification — the NAICS code and rate group WSIB assigns you, which reflects the shared risk of other businesses doing similar work.

There's also a ceiling: for 2026, the maximum insurable earnings per individual is $121,700. Earnings above that amount for any one person aren't subject to WSIB premiums, even though the rest of their pay is. That ceiling moves each year, so it's worth checking current figures on WSIB's site rather than assuming last year's number still applies.

Sub-contractors: the definitional trap

"I only use sub-contractors, so I don't need WSIB" is a common assumption, and it's often wrong. WSIB registration obligations can reach sub-contractors depending on the industry and the actual nature of the working relationship — not just whichever label appears on an invoice. Two businesses that both call their workers "sub-contractors" can land on opposite sides of a registration requirement depending on how the work is actually structured.

We're not going to tell you here whether a specific arrangement counts — that's a status question that depends on facts we don't have and shouldn't guess at in a general guide. What we will say: if you're building a crew out of sub-contractors and haven't had someone confirm your WSIB status, that's worth doing before it becomes a surprise assessment rather than a routine registration.

Where WSIB meets your bookkeeping

WSIB doesn't run through CRA payroll remittances, but it draws on the same underlying numbers — gross payroll by employee, by classification, for the year. If your books are already tracking clean payroll data, pulling insurable earnings for a WSIB premium statement or annual reconciliation is a non-event. If they aren't, it's another reason catch-up bookkeeping tends to snowball: one missing system touches more than just your tax return.

This is the kind of cross-system detail that's easy to lose track of once you've got payroll, HST, and year-end all running at once — which is exactly what our monthly bookkeeping is built to keep in one place, starting at $200/month.

Getting registration right the first time

Register within the 10-day window from your first hire, confirm early whether construction rules apply to your business, and don't take a sub-contractor's self-description as the final word on your obligations. None of this is complicated in isolation — it's the kind of thing that's easy to do correctly on day one and expensive to untangle two years in, once payroll history has to be reconstructed to satisfy an assessment.