Can an estate ask an out-of-province person contesting a will to post security for costs in Ontario?

Yes. Ontario's civil procedure rules allow a court to order a party bringing or contesting a claim — including someone challenging a will — to post security for costs where they live outside Ontario and have no significant assets here to satisfy a costs award if they lose. The idea is to protect the estate (and other beneficiaries) from being left unable to actually collect on a costs order after successfully defending the will, simply because the unsuccessful challenger and their assets are out of reach.

A court has discretion whether to order security, and generally weighs factors such as the apparent strength of the challenge, whether the request is being used as a tactic to make continuing the case financially difficult rather than a genuine concern about collectability, and the challenger's actual connection to Ontario. If ordered, the challenging party typically needs to pay money into court or provide another acceptable form of security before the litigation can continue, and failing to do so can result in the challenge being dismissed. Anyone contesting a will from outside Ontario, or defending against an out-of-province challenger, should raise this possibility with a lawyer early, since it can meaningfully affect litigation strategy and timing.