Can I completely cut an adult child out of my will (or intestate estate) in Ontario?

With a will, you can generally choose to leave nothing to an adult child. Ontario does not have forced heirship rules that automatically entitle children to a share of a parent's estate. However, an adult child who was financially dependent on you — for instance, because of a disability — may have a right to bring a dependant's support claim against the estate, even if you deliberately excluded them.

A court hearing a dependant's support claim looks at factors such as the child's financial need, the size of the estate, and whether the deceased made reasonable provisions. If the court finds the exclusion left the adult child without proper support, it can order a payment from the estate.

Without a will, the intestacy rules do distribute to children as a class — so cutting out a specific adult child requires a will. If a child is deliberately excluded in a will and challenges it, the success of any challenge depends on whether they qualify as a "dependant" under the Succession Law Reform Act.