Corporate tax in Ontario: what the provincial layer adds

Ontario corporate tax is collected by the CRA on the same T2 your corporation already files. There is no Ontario corporate return, no provincial tax authority to file it with, and no second filing date. What Ontario adds is a rate layer inside that return, a sales tax that replaces the GST-plus-PST split with one harmonized filing, and two employer accounts the CRA never sees.

So Ontario is the simplest province to file a corporate return in and an easy one to under-budget for. Most of what the province charges an owner-managed corporation arrives from somewhere other than the CRA.

One return, one collector

Ontario’s corporate income tax is federally administered under a federal-provincial collection agreement. The CRA assesses it, collects it and audits it, and Ontario’s share is calculated on schedules inside the T2. You file once, pay once, and your corporate instalments cover both governments in the same payment. Alberta and Quebec do not work this way — Alberta’s AT1 goes to its own provincial administration and Quebec’s CO-17 to Revenu Québec.

One Ontario filing did move away from the T2. The annual return that keeps a corporation’s registered information current is a corporate-law filing rather than a tax one, and it goes through Ontario’s business registry, not the CRA. It used to travel with the T2 package; now it does not, and it is the filing most often missed.

Two rates on the same dollar

Federally, an eligible CCPC pays 9% on the first C$500,000 of active business income in 2026, and the general rate above that. Ontario applies its own small-business rate and its own general rate to the same income, with its own business limit setting where one ends and the other begins.

The combined rate owners quote each other is the sum of two separately legislated numbers, and either can move in a budget without the other. The federal limit is also ground down by passive investment income and shared across an associated group; Ontario’s treatment of both follows its own legislation.

HST is one tax, one return

Ontario is a harmonized province. The federal and provincial sales taxes are combined into a single 13% HST that you charge, report and remit on one GST/HST return, under one registration, to one government. There is no Ontario provincial sales tax account to open — the structural difference between here and British Columbia, Saskatchewan, Manitoba or Quebec, where the provincial tax is a separate registration with its own administration and return.

The difference shows up in what comes back. A registrant claims input tax credits on the full HST, provincial portion included. In a separate-PST province the provincial tax on what the business buys is generally a cost with no credit against it — the same equipment purchase, different economics, whatever the headline rates say.

The employer layer the CRA does not collect

Run payroll in Ontario and two provincial accounts open outside the CRA’s payroll system entirely. The first is the employer health tax (EHT), a levy on Ontario payroll charged above an exemption available to eligible private-sector employers and shared among associated employers. It has its own registration, its own return and its own instalment rules, and the province administers it — nothing about it passes through your source-deduction remittance.

Workplace Safety and Insurance Board coverage is the second. Registration is mandatory for employers in covered industries, premiums follow an industry classification, and they are charged on assessable earnings that are not the base you used for the CRA remittance. Coverage for an owner or an executive officer is a separate question from coverage for staff — worth settling before an injury, not after.

Both accounts follow payroll, not profit. An owner taking only dividends has no Ontario payroll and no exposure to either — one more input into the salary-or-dividends decision that has nothing to do with rates.

Credits are claimed on the T2, but not all of them start there

Ontario runs its own corporate credits, refundable and non-refundable, covering research and development, media and film production, and apprenticeship and training. They are claimed on Ontario schedules inside the T2, so the CRA processes them with the return — but several require a certificate from an Ontario agency first, applied for separately on that agency’s timetable. The CRA cannot allow a credit whose provincial precondition is unmet, so the failure arrives as a denied claim.

If you expand into or out of Ontario

A province taxes a corporation where it has a permanent establishment — generally a fixed place of business, and in some cases an employee or agent with authority to contract. With one in more than one province, the T2 allocates taxable income among them generally by a formula weighting the gross revenue and the salaries and wages attributable to each establishment, and each province applies its rates to its share. Still one return; more schedules.

The other layers duplicate rather than allocate. Payroll in a second province generally means that province’s workers’-compensation board and whatever payroll levy it runs, on top of Ontario’s. And a corporation incorporated elsewhere that carries on business in Ontario generally registers extra-provincially under Ontario corporate law — a registry step, not a tax filing, that no tax authority will remind you about.

The year at a glance for an Ontario corporation

Illustrative, on a December 31 year-end.

• The T2, six months after year-end — June 30 — carrying federal and Ontario tax together. The balance is generally due at two months, or three for many CCPCs claiming the small-business deduction; instalments cover both.
• The HST return — monthly, quarterly or annual depending on filer type — due one month after the period ends for monthly and quarterly filers.
• T4 and T5 slips by the last day of February, for the calendar year just ended.
• EHT and WSIB on their own provincial schedules, if the corporation runs payroll.
• The Ontario annual return through the business registry, on corporate-law timing rather than tax timing.

The deadline table has the federal dates; the deadlines guide has the reasoning behind them.

What Cadence does

We prepare the T2 with the Ontario schedules on it, calculate both rate layers in the same file, and set instalments covering the federal and provincial pieces together. Where there is payroll, the EHT and WSIB accounts go on the same calendar as the CRA remittances, so no provincial account sits unowned between year-ends. A second province adds allocation and registrations; we handle those too. Corporate tax work and the owner’s personal return are prepared in one relationship, which is how most consultants and agency owners reach us.