Ontario Employer Health Tax (EHT): The Payroll Cost You May Be Calculating Wrong

Most Ontario employers under a million dollars in annual payroll pay no Employer Health Tax, file no return, and reasonably conclude that EHT is somebody else's problem. That conclusion is the source of the risk. The mechanics of Ontario's EHT do not punish the employer who has carefully planned for it; they punish the employer who has not noticed they are about to need to. The exemption sounds generous. The rate looks low. Both are true. What follows is what is also true: a $5-million growth cliff at which the marginal effective rate on payroll jumps from 1.95% to roughly 11.7% for the dollars that cross it; an associated-employer rule that applies to the founder running two incorporated entities under common control; and a set of 2025 reforms that quietly retired the monthly instalment regime entirely. None of that is difficult to calculate. All of it has to be known.

What the EHT actually is

Ontario's Employer Health Tax is a provincial payroll tax on total Ontario remuneration paid by an employer. It funds the Ontario Health Insurance Plan. The taxable entity is the employer, not the employee; EHT does not appear on a T4 slip and is not deducted from wages, which is the structural difference that distinguishes it from CPP and EI source deductions. In OECD terms it is an employer-side contribution comparable to the United Kingdom's Employer National Insurance or France's cotisations patronales. Ontario simply collects it as a dedicated line through the Ministry of Finance rather than bundling it with public-pension contributions, which is the older Canadian convention. The Act dates to 1990 and was framed at the time as a transfer of collection from the individual (the previous OHIP premium) to the employer — a familiar principal-agent move, because the employer is a more reliable remitter than the household.

The rate schedule

The applicable rate is set by total Ontario remuneration — that is, payroll before the exemption is taken into account — not by the taxable amount that remains after the exemption is applied. Once the rate is determined from this table, it applies as a single flat rate to the taxable remuneration; the lower bands are not summed marginally.

The practical consequence of the lookup-by-total-payroll structure is that the lower bands rarely apply to private-sector EHT-paying employers. The $1 million exemption already shelters every private employer whose total Ontario remuneration is below $1 million — comfortably above the $400,000 threshold at which the 1.95% top rate kicks in. By the time an employer is paying EHT at all, they are almost always paying it at 1.95%. The lower bands matter chiefly for employers who do not have access to the exemption: public-sector bodies, or members of an associated group whose combined remuneration has crossed $5 million and triggered the eligibility cliff.

A worked example. An employer with $1.4 million in Ontario payroll, claiming the full $1 million exemption, has $400,000 of taxable remuneration. Total payroll exceeds $400,000, so the applicable rate is 1.95%. Applied to the taxable base: $400,000 × 1.95% = $7,800 in EHT. There is no graduated blending. At $2 million total payroll the same logic produces 1.95% × $1 million = $19,500. The arithmetic is, in the end, simpler than that of most provincial payroll taxes; the structural complications all live in the exemption rules and the cliff, not in the rate schedule.

The exemption, and how it can be lost

The $1 million annual exemption is available to private-sector Ontario employers. It is not available to public bodies (municipalities, hospitals, school boards, universities, colleges) and it is pro-rated for short tax years and new employers. There are two ways an employer who would otherwise qualify loses access to it.

The first is the $5-million cliff. An employer whose annual Ontario remuneration exceeds $5 million is no longer eligible for any exemption, and EHT is owed on the full payroll. The cliff is sharper than it looks. An employer at $4.9 million pays EHT on $3.9 million of taxable remuneration; at $5.1 million, the employer pays EHT on the full $5.1 million. The marginal $200,000 of payroll growth carries roughly $23,000 of additional tax — an effective marginal rate around 11.7% on the dollar that crossed the threshold. There is a real-world incentive in this number to manage payroll growth carefully when an employer is approaching $5 million, particularly through year-end timing of bonuses or new hires that could otherwise be January business.

The second is the associated-employer rule, which is the section most generic guides handle badly.

The associated-employer trap

Under the Employer Health Tax Act (Ontario) and its regulations, "associated employers" — broadly, corporations controlled by the same person or group — share a single $1 million exemption. The association test is anchored, by reference, to the federal Income Tax Act section 256 association rules. This was a deliberate drafting choice in the original Act and it has the practical effect that any CRA association determination for small-business-deduction purposes also governs the EHT exemption.

The failure mode is the SMB founder running two or three incorporated entities — typically a holding company that pays salary to common ownership, plus one or two operating companies — and assuming each entity gets its own $1 million exemption. It does not. The combined Ontario remuneration is what counts.

The dollar exposure in this example is small. The structural exposure is not — the same arrangement at $4.5 million combined payroll grows the EHT bill into the tens of thousands, and at $5.1 million it loses the exemption entirely.

Associated employers must file an associated-employer agreement specifying how the $1 million exemption is allocated among them.

What the 2025 reforms changed

Three reforms took effect on 1 January 2025 and quietly reshaped the compliance burden. They are easy to miss because they did not change the rate schedule.

Instalments were removed. Under the previous regime, employers with annual Ontario remuneration above an instalment threshold (originally $600,000, raised to $1.2 million for the 2021–2024 period) were required to remit monthly instalments. As of 1 January 2025, the instalment regime has been retired in its entirety. Employers now file an annual EHT return only. Any older guide that warns about the "instalment trap" — including last week's competitor coverage, in places — is describing a compliance regime that no longer exists.

A new associated-employer exemption calculation. Each associated employer's exemption is now capped at the lesser of (a) its allocated share of the $1 million exemption under the associated-employer agreement, or (b) its own total Ontario remuneration. The practical consequence: an associated employer cannot use exemption capacity allocated to it that exceeds its actual remuneration. Where the old rule could in some structures over-shelter remuneration through allocation choices, the new rule pegs each entity's claim to its own payroll. The total exemption available across associated employers remains $1 million, but it cannot now be parked in a low-payroll affiliate to shelter payroll elsewhere.

An acquisition-year rule. In the year of an acquisition, only companies that are actually associated with each other during that year must combine payrolls to test the $5 million ineligibility threshold. The previous rule had effectively required full-year combination on the basis of association at any point in the year, which produced the awkward result of an acquirer losing the exemption mid-year because it had bought a target that, on combined annualised payroll, crossed $5 million. The 2025 amendment defers that combination until the first full year of association.

The annual return for the 2026 tax year is due 15 March 2027. Interest on outstanding balances is compounded daily at Ontario's prescribed rate, which the Ministry of Finance sets quarterly — currently 7% annualised for the 1 April to 30 June 2026 period. The penalty regime is mild relative to CRA's payroll source-deduction enforcement, but it is not nothing — the daily compounding compounds.

A note on Quebec

Quebec's Fonds des services de santé contribution is the closest provincial cousin and the natural comparator for any Hibiscus customer running Ontario and Quebec payrolls in parallel. Two things distinguish FSS from Ontario EHT. The FSS rate is set by sector (the payroll-services sector pays 4.26%; manufacturing pays less), where Ontario applies a single graduated schedule regardless of industry. And FSS uses an income-based exemption mechanism rather than a payroll threshold, with no equivalent of Ontario's clean $1 million exemption. The structural similarity is that both provinces collect through the employer; the practical similarity ends there. The Ontario rate structure will feel more predictable to a Quebec employer expanding west than the FSS will feel to an Ontario employer expanding east.

Federally regulated employers — banks, telecoms, interprovincial transport — pay Ontario EHT on their Ontario employees regardless of federal labour-code oversight. Federal jurisdiction does not displace provincial payroll taxes.

What we do at Hibiscus

Hibiscus HR tracks total Ontario remuneration across an associated-employer group, applies the post-2025 exemption calculation, and flags when combined payroll is approaching the $5 million ineligibility threshold. The annual return generates from payroll data already in the system. The associated-employer agreement is held against the tenant and surfaces in the EHT report. None of that is the most interesting feature in our payroll module, and it is not why most customers buy Hibiscus. It is, however, why a customer who already runs payroll with us is unlikely to discover an EHT problem the way the average Ontario SMB still does — at the year-end close, when the number is bigger than expected.