Does an agreement's governing law clause actually matter if both parties are in Ontario anyway?

Yes, even though it might seem like an unnecessary formality when both sides are already Ontario businesses. A governing law clause states which jurisdiction's law will be used to interpret the agreement, and while Ontario law would likely apply by default in many purely domestic scenarios anyway, an express clause removes any argument about it later, which matters more than it sounds like it should if a dispute actually arises.

It also does more work than people expect: the business itself, its assets, its employees, or its customers can have connections to other provinces or countries even when the buyer and seller are both Ontario entities, and a clear governing law clause (often paired with a clause on which courts have jurisdiction to hear disputes) heads off an argument about the wrong forum or the wrong law being applied to a dispute that touches more than one place. It also interacts with other clauses in the agreement, since certain interpretive rules and default terms genuinely differ between jurisdictions even within Canada.

Treating the governing law clause as boilerplate to skip past is a common but avoidable mistake — a Treadstone business lawyer reviewing your agreement should confirm it says exactly what you intend, not just assume it's fine because everyone involved happens to be in Ontario today.