A Canadian will is invalid if it fails the witnessing rules of the province where you signed it, was signed under undue influence, or the testator lacked testamentary capacity at the time of execution. Courts do not fix flawed wills — the estate passes under intestacy rules instead, often to people the deceased would never have chosen.
Why provincial law matters more than you think
Estate law in Canada is not federal. Each province enacts its own Wills Act (or equivalent), and the execution rules differ enough that a will properly signed in British Columbia can be invalid if the testator later moves to Ontario — or vice versa, depending on the circumstances. British Columbia's Wills, Estates and Succession Act (WESA) s. 37, for example, gives courts a curative power to admit a document that does not fully meet formal requirements if there is clear evidence the deceased intended it as their will. Ontario's Succession Law Reform Act (SLRA) has no equivalent provision, so Ontario courts apply the formal rules strictly. Knowing which province's law governs your will is the first practical step.
Mistake 1: wrong number of witnesses or a beneficiary witnesses the will
Every formal will in Canada requires two adult witnesses present at the same time the testator signs. A witness who is also a beneficiary under the will — or the spouse of a beneficiary — triggers the gift-purging rule. In Ontario, s. 12 of the SLRA voids the specific gift to that witness-beneficiary while leaving the rest of the will intact. In Alberta, the Wills and Succession Act (WSA) s. 18 operates similarly. The witness themselves does not lose the right to act as a witness; only the bequest is struck. Notaries, lawyers, and other uninterested adults are the safest choice.
The "same time and place" requirement trips people up more often than the beneficiary rule. One common error is having the testator sign first and then routing the document to each witness separately for their signature. That does not satisfy the simultaneous-presence requirement in any province. All three signatures — testator plus two witnesses — must happen in a single session.
Mistake 2: the holograph will is not entirely in the testator's own handwriting
Holograph wills (entirely handwritten and signed by the testator, with no witnesses required) are valid in Ontario, Alberta, British Columbia, Manitoba, Saskatchewan, and several other provinces — but not in all. Prince Edward Island does not recognize holograph wills; neither does British Columbia under its pre-WESA regime for deaths before April 2014.
Where holograph wills are permitted, the entire document must be in the testator's handwriting. Pre-printed forms filled in by hand do not qualify. A will typed on a computer with a handwritten signature at the bottom is not a holograph will — it is a formal will that fails for lack of witnesses. Courts have consistently refused to save hybrid documents because the statutory requirement for holograph wills is unambiguous: the entire body of the will, not just the signature, must be in the testator's own hand.
Dates on holograph wills matter too. An undated holograph will can cause problems if there are multiple versions in existence or if testamentary capacity is challenged. Write the full date — day, month, and year — in your own hand.
Mistake 3: lack of testamentary capacity
Canadian courts apply the test from Banks v Goodfellow (1870) LR 5 QB 549, which Canadian courts have adopted and continue to apply. A testator must understand the nature of making a will, the general extent of the estate, the natural objects of their bounty (typically family members), and how the will distributes the estate. All four elements must be present at the moment of signing.
Capacity is assessed at the time of execution, not at the time of death. A testator with dementia can still execute a valid will during a lucid interval, provided there is evidence — usually a physician's note or a lawyer's capacity assessment — that they met the Banks v Goodfellow standard at that specific moment. Conversely, a testator who appears perfectly healthy but is experiencing early cognitive decline may lack capacity in law even though nothing is visibly wrong.
Challenges on capacity grounds are among the most litigated estate disputes in Canada. In Laszlo v Lawton 2013 BCSC 305, the BC Supreme Court declared a will invalid precisely because the proponents could not prove the testator had capacity — at the time she gave instructions — to appreciate the claims of the natural objects of her estate. The decision is a reminder that the burden of proving capacity rests with the proponent of the will, and that contemporaneous evidence (physician notes, solicitor observations) can be decisive either way.
Mistake 4: the will was signed under undue influence
Undue influence in will-making is distinct from undue influence in contract law. Canadian courts require proof that the testator's free will was overpowered — not merely that they were persuaded or guided. The Supreme Court of Canada addressed the burden of proof in Vout v Hay [1995] 2 SCR 876, holding that where suspicious circumstances are raised (such as the main beneficiary arranging and being present at the signing), the presumption of due execution is spent and the proponent of the will must prove that the testator had knowledge and approval of the will's contents — and, where capacity is also in issue, that the testator had capacity. The burden of proving actual undue influence, however, always rests with the challenger.
Family caregivers, new romantic partners, and adult children who have taken over financial management of an elderly parent's affairs are the people most commonly named in undue-influence challenges. The risk is not theoretical: Ontario reported a spike in contested estates involving caregiver beneficiaries after 2018. Solicitors routinely ask to see a testator privately before execution, specifically to establish that no one is standing over them with instructions.
Mistake 5: the will was revoked by a subsequent marriage — or the revocation was accidental
At common law, marriage once revoked all previous wills automatically — but the majority of Canadian provinces have now abolished that rule by statute. Ontario repealed the automatic-revocation-by-marriage provisions of the SLRA (ss. 15(a) and 16) effective January 1, 2022 under Bill 245. Alberta eliminated automatic revocation by marriage when the Wills and Succession Act came into force on February 1, 2012. British Columbia took the same position under WESA s. 55 for deaths after April 2014. Testators in these provinces can marry without voiding an existing will — though they should still review and update the will to reflect their new circumstances. Some other provinces retain the common-law rule or have older statutes still in force, so checking the law in the specific province remains important.
The flip side — accidental revocation — is less discussed but just as damaging. A testator who crosses out provisions with the intention of revising the will without making a new one may end up with no valid will at all, depending on whether the alterations satisfy the provincial rules for testamentary alterations. Under SLRA s. 18, alterations are not effective unless they are separately signed and witnessed in the margins. An unmarked red pen through a clause is not a valid alteration in Ontario.
Mistake 6: the document is ambiguous about who gets what
Strict formal execution is not enough. A will that names beneficiaries or describes property in vague or contradictory terms creates litigation risk even if it is technically valid. Gifts to "my children" in a blended family without specifying whether step-children or adopted children are included have generated years of estate litigation across Canadian provinces. A gift of "the house" when the testator owns multiple properties at death raises questions that the courts must resolve — often expensively.
Residue clauses are particularly prone to drafting gaps. A will that distributes specific assets but forgets to include a residue clause means anything acquired after signing passes under intestacy. In Ontario, the intestacy rules under the SLRA Part II would distribute the residue based on surviving relatives in a fixed order, which may bear no resemblance to the testator's actual wishes.
How to get it right
Start with a clear, complete document drafted for your province, reviewed against the applicable Wills Act before signing. A free Canadian last will and testament template from forms-legal.com covers the standard formal execution requirements and includes fields for residue, guardianship, and executor appointment — a practical starting point before a lawyer reviews the final version.
Sign with two adult, non-beneficiary witnesses present at the same time. Store the executed will somewhere an executor can find it — the safest option in Ontario is filing with the Ontario Court of Justice Estates Office under the Estates Act R.S.O. 1990, c. E.21, which maintains a will-deposit registry for a nominal fee. BC offers a similar registry through the Vital Statistics Agency.
Revisit the will after major life events: marriage (which no longer automatically revokes a will in Ontario, Alberta, or BC, but which may still do so in other provinces and which always warrants a review of your estate plan), divorce (which revokes gifts to a former spouse in most provinces but does not revoke the rest of the will), and significant changes in assets or family circumstances. The will that was perfectly drafted at 35 may be materially deficient at 60.
Related documents worth knowing
An executor who needs authority to act before probate is granted may need a Grant of Administration or, in smaller estates, a Small Estate Affidavit — available for estates below provincial thresholds ($150,000 in Ontario as of 2021). A Codicil to Last Will and Testament is the correct instrument for minor amendments post-execution; it requires the same formal execution as the original will.
Testamentary capacity and undue influence are easier to head off than to litigate. A lawyer-witnessed will with contemporaneous capacity notes costs a few hundred dollars. Contesting a will in Ontario's Estates List typically runs from $50,000 to several hundred thousand dollars in legal fees before the matter resolves.
Need the document itself? Download the free template →
This article is general information, not legal advice — see our accuracy & editorial policy. Confirm the cited law is current before relying on it.