An American company took your money, breached your contract or damaged your business. Before you sue a US defendant, Ontario law asks two questions that have nothing to do with the merits: can an Ontario court take the case, and can you serve the claim properly? A third question matters even more, and most people ask it last. This guide walks through all three.

Can You Sue a US Defendant in Ontario at All?

Ontario courts do not take jurisdiction simply because the plaintiff lives here. The governing framework comes from Club Resorts Ltd. v. Van Breda, 2012 SCC 17, which requires a real and substantial connection between Ontario and the claim.

The Supreme Court built that test around presumptive connecting factors. Establish one and jurisdiction is presumed, subject to rebuttal.

Whether you can sue a US defendant in Ontario turns on that connection, not on where you happen to feel the loss.

The four presumptive connecting factors

Only one of the four needs to apply before you may sue a US defendant here. For a tort claim, the Court listed them at paragraph 90:

(a) the defendant is domiciled or resident in the province; (b) the defendant carries on business in the province; (c) the tort was committed in the province; and (d) a contract connected with the dispute was made in the province.

Notice what is missing. Damage suffered in Ontario is not, on its own, a presumptive connecting factor.

That single point defeats a great many claims. An Ontario business that loses money here because of something an American company did in Texas has not, without more, established a basis to sue that US defendant in Ontario.

Plaintiffs find this counter-intuitive, and understandably so. The harm is real and it happened here, but harm alone will not support suing a US defendant in an Ontario court.

Carrying on business is not the same as having a website

The second factor tempts people, because almost every American business is reachable online. The Court closed that door at paragraph 87:

Active advertising in the jurisdiction or, for example, the fact that a Web site can be accessed from the jurisdiction would not suffice to establish that the defendant is carrying on business there.

Carrying on business requires actual rather than virtual presence, such as an office here or regular visits. The Supreme Court reaffirmed that approach in later authority.

So you cannot sue a US defendant in Ontario simply because its website loads in Toronto or it runs ads that Canadians see.

However, no office does not mean no business. In Toronto Star Newspapers Limited v. OpenAI Inc., 2025 ONSC 6217, the Superior Court took jurisdiction over American entities with no Ontario office, on the strength of real Canadian revenue, Canadian users and website terms governed by Canadian law. That decision is only at the lower court, so treat it as an indicator rather than settled law.

Substantial Canadian revenue and a Canadian user base can therefore be enough to sue a US defendant in Ontario, even without a physical footprint.

How a defendant rebuts the presumption

A presumptive factor creates a presumption, not a conclusion. At paragraph 95, the Court said the defendant must

establish facts which demonstrate that the presumptive connecting factor does not point to any real relationship between the subject matter of the litigation and the forum or points only to a weak relationship between them

That route is now considerably more important. In Sinclair v. Venezia Turismo, 2025 SCC 27, the Supreme Court held that jurisdiction must be assessed defendant by defendant, with no bootstrapping from a co-defendant’s attornment or connections. An Ontario contract can still ground presumptive jurisdiction where the events giving rise to the claim flow from it, but the presumption will be rebutted where the defendant shows the contract’s connection to the dispute and to that defendant is weak or non-existent.

The practical translation is blunt. Signing a contract at your kitchen table in Mississauga does not, by itself, let you sue every US defendant in the chain in Ontario.

That is now the main battleground where an Ontario plaintiff sues several American parties at once. Each defendant gets its own analysis.

Forum Non Conveniens: The Second Hurdle

Winning on jurisdiction does not end the argument. A US defendant sued in Ontario has a second way out, and can ask the court to decline the case in favour of an American court.

The burden sits on the defendant, and it is a demanding one. The alternative forum must be clearly more appropriate, not merely equally suitable, because as the Court put it at paragraph 109, the standard reflects

an acknowledgment that the normal state of affairs is that jurisdiction should be exercised once it is properly assumed

Courts weigh the location of the parties and witnesses, the cost of moving the case, the effect on how the litigation runs, the governing law, the risk of conflicting judgments, and problems of recognising and enforcing any eventual judgment.

Note the sting in that last factor. Where a US defendant has its assets cuts both ways when you sue in Ontario, because the enforcement problem that worries you is also an argument the defendant runs against this forum.

Juridical advantage carries little weight. Preferring Ontario’s costs rules or procedure is not a reason to sue a US defendant here rather than at home.

Serving a US Defendant

Suing a US defendant from Ontario founders on service more often than on jurisdiction. The rules here are mechanical rather than discretionary, which makes the mistakes avoidable.

Rule 17 and service outside Ontario

Rule 17 of the Rules of Civil Procedure governs. Rule 17.02 lets you serve an originating process outside Ontario without leave where the claim falls within an enumerated category, including claims about Ontario property, contracts made in Ontario or governed by Ontario law, and torts committed in Ontario.

That rule is the route most plaintiffs use to sue a US defendant from Ontario without a preliminary motion.

Where the claim does not fit a category, rule 17.03 requires leave of the court on a motion supported by evidence of the connection.

One historical ground deserves a warning. Damage sustained in Ontario is no longer a stand-alone route to serve a defendant outside the province without leave, and in any event Van Breda had already stripped it of jurisdictional force.

A defendant who wants to fight responds under rule 17.06, moving before delivering a defence to set aside service or stay the action. Bringing that motion is not, by itself, attornment to Ontario’s jurisdiction.

The Hague Service Convention

Both countries are parties to the Hague Service Convention, and where it applies, compliance is mandatory. Anyone suing a US defendant from Ontario has to follow it.

You cannot improvise a method that suits you better, and actual notice does not cure defective service.

The United States designates a Central Authority through the Department of Justice, which outsources the work of serving private individuals and companies to a contractor. That explains both the fee and the timeline, which routinely runs to months rather than weeks.

Canada has a federal Central Authority and a designated authority in each province and territory, and a request may go either route. Service in Ontario runs through the Ministry of the Attorney General.

What about service by mail?

The United States has not objected to the Convention’s postal channels, so the treaty does not prohibit mailing documents to an American defendant. That is only half the answer, though.

The Convention permits service by mail rather than authorising it. Whether you may actually use it depends on Ontario’s own rules, so treat Central Authority service as the default and mail as a supplement.

Forum Selection and Arbitration Clauses

Read the contract before you do any of this. A forum selection clause can end your plan to sue a US defendant in Ontario before it starts.

American standard forms routinely designate a US court or arbitration seat, and Ontario courts generally enforce those clauses.

The framework comes from Z.I. Pompey Industrie v. ECU-Line N.V., 2003 SCC 27. Where a valid exclusive forum selection clause applies, the ordinary analysis is displaced and the court gives effect to the clause unless the plaintiff shows strong cause not to.

Douez v. Facebook, Inc., 2017 SCC 33 softened that in consumer cases. The Court took account of gross inequality of bargaining power and the nature of the rights at stake, and declined to enforce a California clause against a consumer.

Business readers should not over-read that decision. Ontario courts continue to enforce forum selection clauses between sophisticated commercial parties, and Douez will rarely help a company that signed an American supplier’s standard terms.

Arbitration clauses follow their own path. In Uber Technologies Inc. v. Heller, 2020 SCC 16, the Supreme Court refused a stay in favour of arbitration where the cost of starting the arbitration was so high that the challenge would never be heard, and found the clause unconscionable.

Worth knowing as well: neither Canada nor the United States is bound by the Hague choice of court treaty, so these questions run on common law rather than convention.

The Question That Should Come First: Where Are the Assets?

Most people decide where to sue and then think about collecting. Reverse that order, because suing a US defendant in Ontario is worth doing only if the judgment can actually be collected.

There is no Canada-United States treaty on the reciprocal enforcement of money judgments. Recognition of an Ontario judgment is a matter of state law, and most states have adopted a version of a uniform recognition statute while the rest apply common law.

The jurisdictional filter runs again

Here is the trap. A US court asked to recognise your Ontario judgment will apply its own standard for whether Ontario had personal jurisdiction over that US defendant, informed by American due process requirements.

A defendant who ignored the Ontario action entirely has preserved that objection. It can raise the point for the first time at the enforcement stage, years later.

So an Ontario judgment against a US defendant with thin Ontario contacts can be an expensive piece of paper. If the defendant has no Canadian assets, filing in its home state may be faster overall, however much that feels like surrender.

The procedural trade-offs cut both ways too. Ontario is a loser-pays jurisdiction, so a successful plaintiff recovers a meaningful share of its legal costs, which almost never happens in an American court.

American procedure, on the other hand, offers far broader discovery, including depositions of multiple witnesses. Getting evidence from American non-parties for an Ontario action usually proceeds by letters rogatory or an application to a US district court, and either route is slow and expensive.

The asymmetry runs the other way

Canada is comparatively generous in the opposite direction. Under Beals v. Saldanha, 2003 SCC 72, Ontario enforces a foreign judgment where the foreign court had a real and substantial connection, subject only to narrow defences of fraud, denial of natural justice and public policy.

The lesson for an Ontario business on the receiving end is simple. Ignoring an American lawsuit is dangerous, because the resulting default judgment may well be enforceable here.

What to Do Next: When to Call a Lawyer

Before you sue a US defendant from Ontario, work through the following in order.

Start with collection, not with pleadings. Find out where the defendant’s money, receivables, real property and bank accounts actually are, because that answer often decides the forum by itself.

Then map your connecting factors honestly. Where was the contract made, where was the tort committed, and does this defendant, specifically, carry on real business in Ontario? Weak answers point toward suing in the United States.

Protect the limitation period while you decide whether to sue the US defendant in Ontario or in its own state. Ontario’s basic period is two years from discovery, with a fifteen-year outside limit, and American periods vary by state and by claim. A jurisdiction argument can easily eat a year.

Budget realistically for service. Central Authority service on a US defendant takes months, so start it early rather than discovering the delay after a deadline has passed.

Finally, if you are the one being sued in the United States, take advice before deciding whether to respond. Staying out preserves a narrow jurisdictional objection at the Ontario recognition stage, but it forfeits every defence on the merits, and Ontario may well enforce the resulting default judgment.

Cross-border disputes reward the party that thought about enforcement first. If you need to sue a US defendant from Ontario, or an American claim has landed on your business, contact Cowan for a clear read on jurisdiction, service and where the judgment would actually be worth something.