Can a Will Be Challenged in Ontario? The Legal Grounds for Estate Litigation

Not every unfair or surprising will is legally invalid. In Ontario, a will can only be challenged on recognized legal grounds, and courts generally start from the position that a properly executed will is valid.

That means evidence matters. Suspicion alone is not enough.

The Starting Presumption

If a will appears to have been properly signed and witnessed, the law generally presumes it is valid unless a challenger can establish a recognized problem.

That is why will challenges are often difficult, expensive, and heavily fact-driven.

Who Can Challenge a Will

Not everyone who dislikes the result has standing to challenge it.

Standing usually exists for people such as:

• beneficiaries under the disputed will
• beneficiaries under an earlier will
• people who would inherit on intestacy if the will were set aside
• dependants with support-related claims

Main Grounds for Challenge

1. Lack of Testamentary Capacity

The testator must have had the mental capacity to make a will at the time of signing.

That usually means understanding:

• that they were making a will
• what property they generally owned
• who might naturally expect to benefit
• the effect of the decisions they were making

Capacity is time-specific. A person may lack capacity at one point and have it at another. A diagnosis such as dementia does not automatically answer the legal question.

2. Undue Influence

Undue influence is not just advice, pressure, or persuasion. It is influence that overcomes the testator’s free will.

Examples that often raise concern include:

• isolation of the testator
• dependency on a beneficiary or caregiver
• threats or coercive pressure
• a beneficiary driving the entire will-making process

Proving undue influence can be difficult because it often happens privately and must be inferred from surrounding facts.

3. Suspicious Circumstances

Suspicious circumstances are red flags that cause a court to look more closely at whether the will really reflects the testator’s wishes.

Common examples include:

• a major departure from earlier wills without clear explanation
• a principal beneficiary heavily involved in preparing the will
• unusual haste
• communication barriers
• visible confusion or vulnerability

4. Lack of Knowledge and Approval

Even if the testator had general capacity, a will may still be challenged if they did not actually understand and approve its contents.

This issue can arise where a person signs a document:

• without properly reading it
• in a language they do not understand
• while relying entirely on someone else’s explanation

5. Fraud or Forgery

These are less common but serious grounds. A forged signature or a will produced through deliberate deception can be set aside.

6. Improper Execution

Ontario wills must generally comply with formal execution rules. If the document was not properly signed and witnessed, validity may be challenged, subject to Ontario’s curative powers in some cases.

7. Revocation Issues

Sometimes the dispute is not about whether the document was validly made, but whether it was later revoked by a later will, a revocation document, marriage in some contexts, or intentional destruction.

Dependant Support Claims

A dependant support claim is different from a validity challenge.

In that situation, the claimant may accept that the will is valid but argue that the deceased failed to make adequate provision for a dependant. That can include certain spouses, common-law partners, and dependent children.

Evidence That Usually Matters Most

The strongest will challenges are usually built on evidence, not family opinion.

Important evidence often includes:

• medical records
• cognitive assessments
• lawyer’s notes
• witness evidence
• earlier wills
• surrounding communications

Why the Drafting Lawyer’s Notes Matter So Much

The notes of the lawyer who prepared the will are often central.

Good notes may show:

• who gave the instructions
• whether the lawyer met the testator alone
• how the testator explained their wishes
• what the lawyer observed about alertness and understanding

Those notes can either strengthen the will dramatically or, in some cases, expose real concerns.

What the Process Usually Looks Like

Will challenges often involve:

1. preserving the estate position early
2. obtaining records and the drafting file
3. assessing evidence before taking a firm litigation position
4. negotiation or mediation
5. court proceedings if settlement is not possible

Many disputes settle before trial, but even then the process can be expensive and emotionally difficult.

Cost and Risk

Estate litigation often consumes a significant amount of time, money, and family goodwill.

That is why a serious review of the actual legal grounds is essential before launching or defending a challenge. Not every concern becomes a successful case.

If a Challenge Succeeds

If the challenged will is set aside, the result is often one of two things:

• an earlier valid will governs, or
• the estate falls into intestacy if no earlier valid will exists

That is why our guide on dying without a will in Ontario becomes important in many estate disputes. If you are reviewing your own estate plan for vulnerability, our article on updating your will after marriage, divorce, and children is a useful preventive resource.

This article is for informational purposes only and does not constitute legal advice. Estate litigation is highly fact-specific and should be assessed with experienced legal guidance.