What do I need to show a court to freeze someone's assets before trial with a Mareva injunction in Ontario?

A Mareva injunction is an extraordinary court order, developed through the common law and available under the court's general injunction powers, freezing a defendant's assets before trial to stop them from being dissipated or moved out of reach while a claim is being decided - not a way to secure payment early, but a way to preserve the status quo so a future judgment isn't rendered meaningless. Because it can seriously disrupt a defendant's life and business before they've had a chance to defend themselves, courts apply a demanding, multi-part test before granting one.

You generally need to show you have a strong, arguable case on the merits, that the defendant has assets within the court's reach, and - critically - that there's a real risk those assets will be dissipated, hidden, or moved out of the jurisdiction before trial if the order isn't made, rather than just a general fear the defendant might not pay a judgment someday. You also generally have to show that damages alone wouldn't adequately protect you if the assets disappear, and you must fully and frankly disclose all relevant facts to the court, including anything that might hurt your own application, since these orders are often sought urgently and without notice to the other side.