Does a foreign corporation need to register in Ontario before it can buy real estate here?

Generally, yes - a corporation incorporated outside Ontario that wants to properly hold and deal with real estate here typically needs to extra-provincially register under Ontario's corporate registration framework, governed in part by the Corporations Information Act, before it carries on that kind of business in the province in its own name. This is a separate requirement from, and works alongside, any considerations under the federal foreign buyer ban or Ontario's Non-Resident Speculation Tax, which look at beneficial ownership and control rather than at whether the corporation is properly registered to do business.

Failing to register when required can create its own complications - both practical, in terms of dealing with government agencies and financial institutions, and legal, since operating without required registration is itself a compliance issue distinct from the property purchase itself. This is a step that is sometimes overlooked amid the bigger tax and foreign-buyer-ban questions, even though it is a foundational corporate law requirement.

Confirm your corporation's registration status and requirements with a lawyer well before closing, treating it as a distinct step from the tax and foreign-buyer-ban analysis.