Challenging a Probated Will in Ontario: Why Timing Is Everything

A Recent Court of Appeal Decision Underscores a Critical Deadline

In Elizabeth Casey Cooke Family Trust v. Dioguardi, 2026 ONCA 85, the Ontario Court of Appeal delivered a decision that every estate beneficiary should be aware of. The case involved a will that contained a drafting error — the lawyer who prepared it failed to include a proper alternative disposition for a portion of the estate. By the time the affected beneficiaries tried to do something about it, it was too late.

What Happened

James Cooke instructed his lawyer to prepare a new will in 2018 that would leave 10 percent of the estate residue to each of two beneficiaries, contingent on his wife predeceasing him or dying within 30 days. The lawyer drafted the will with this condition but did not include any alternative provision for what would happen to those gifts if the condition failed — that is, if the wife survived.

When the wife survived, the 10 percent gifts failed, creating a partial intestacy. The intended beneficiaries, who expected to receive their share of the estate, got nothing. They sued the lawyer for negligence.

The Problem: Collateral Attack on a Probated Will

The Court of Appeal held that the negligence action was effectively a collateral attack on the probated will. Once a will has been probated — that is, once the court has issued a Certificate of Appointment validating the will — it carries a strong presumption of finality. The proper remedy for a defective will is to seek rectification before probate is granted, not to sue the lawyer after the fact.

The Court emphasized the principle of finality in probate proceedings. The legal system depends on the certainty that once a will is probated, it can be relied upon by executors, beneficiaries, and third parties. Allowing negligence actions to effectively rewrite probated wills through the back door would undermine this certainty.

The Takeaway for Beneficiaries

This case sends a clear message: if you believe there is a problem with a will — whether it is a drafting error, an ambiguity, or a concern that the will does not reflect the deceased’s true intentions — you must act before probate is granted. Once the Certificate of Appointment has been issued, the window to challenge the will narrows dramatically.

In practical terms, this means that beneficiaries who receive notice of a probate application should review the will carefully and promptly. If something does not look right, legal advice should be sought immediately. Filing an objection or a notice of appearance before the Certificate of Appointment is issued preserves the beneficiary’s right to challenge the will.

The Takeaway for Estate Planners

The Cooke case is also a cautionary tale for lawyers and other professionals involved in preparing wills. A conditional gift without an alternative disposition is a drafting oversight that can have devastating consequences for intended beneficiaries. Every will should be carefully reviewed to ensure that all contingencies are addressed and that the testator’s wishes will be carried out regardless of the order in which family members pass away.

For anyone involved in an estate dispute — whether as a beneficiary, executor, or estate trustee — the lesson from this case is straightforward: timing matters, and early legal advice can make the difference between protecting your rights and losing them entirely.