Can a dependant make a claim against an estate in Ontario if they were left out of the will?

Yes. Ontario's Succession Law Reform Act allows certain dependants of a deceased person to make a claim against the estate for adequate support if the will (or the result of intestacy) fails to provide for them. Dependants who may qualify include a spouse, a same-sex partner, a parent, a sibling, or a child — including adult children who can demonstrate actual financial dependence on the deceased.

The claim must be commenced within six months of the date of the probate certificate. A court assessing the claim will consider a range of factors, including the claimant's financial need, the size of the estate, the deceased's obligations, any other means of support available to the claimant, and the competing claims of other beneficiaries and creditors.

If successful, the court may order a lump sum or periodic payments out of the estate. Dependant support claims are one of the primary ways courts can override a testator's choices, so executors must be aware of potential claimants before making distributions.