Introduction

Every civil litigator eventually confronts the question: When exactly did the clock start ticking? The answer has serious consequences. A misstep in the calculation of a limitation period can mean the difference between a viable action and a dead claim.

In 2021, the Supreme Court of Canada issued a game-changing ruling in Grant Thornton LLP v. New Brunswick, 2021 SCC 31^[1], clarifying the threshold for discoverability in limitation periods. Though the case arose from a failed audit and the Province of New Brunswick’s $50 million loss, the legal principles it laid down have far-reaching implications that extend well beyond accounting malpractice.

This blog delves deep into the core holding of Grant Thornton, explores its significance in the broader legal profession, and examines ten distinct practice areas where this ruling is likely to have transformative effects. In each, the key takeaway is this: if a client has enough facts to plausibly infer wrongdoing, the countdown has begun.

I. The Decision at a Glance

In Grant Thornton, the Province of New Brunswick sued its auditor after relying on an allegedly negligent audit report that led the Province to issue $50 million in loan guarantees. The loans defaulted. The Province eventually obtained a second opinion suggesting the original audit failed to identify massive financial misstatements. Over two years after receiving that second opinion, it issued a statement of claim.

The auditor moved to dismiss the case on the basis that the two-year limitation period had expired. The key issue was when the Province “discovered” its claim under New Brunswick’s Limitation of Actions Act^[2], which defines discovery as the point when the claimant knew or ought reasonably to have known:

     (a) that an injury, loss or damage occurred;
     (b) that the loss was caused by an act or omission; and
     (c) that the act or omission was that of the defendant.

Justice Moldaver, writing for a unanimous Court, ruled that a plaintiff need not have certainty of liability, nor knowledge of every legal element of a cause of action. The test is whether the plaintiff had actual or constructive knowledge of the material facts from which a plausible inference of liability could be drawn.

In applying this standard, the Court found that the Province had enough information to infer negligence once it received the second auditor’s report—even if it lacked access to the original auditor’s working papers or full legal advice. Because it waited over two years from that point to issue the claim, the action was statute-barred.

II. The Doctrinal Significance

Grant Thornton repositions the balance in limitation law. While some lower courts had been drifting toward a more demanding standard—requiring knowledge of all constituent elements of a claim—the Supreme Court stopped that trend cold^[3].

Instead, the Court emphasized a standard grounded in proportionality and practical fairness, making clear that what matters is plausibility, not certainty. The threshold for discoverability sits above mere suspicion but does not require conclusive proof. A claim is discoverable once the plaintiff can reasonably connect the dots between the harm suffered and the potential liability of the defendant.

This approach codifies a pragmatic rule: once a client has the material facts and can infer that a specific defendant may have caused the loss, the two-year limitation period is triggered. The implications for legal practice are significant.

III. Ten Legal Areas Affected by Grant Thornton

The reach of Grant Thornton extends across nearly every corner of civil practice. Here are ten areas where I expect its principles to reshape the limitation period analysis:

1. Solicitor’s Negligence in Estate Planning and Litigation

In estate matters, clients often rely on solicitor-drafted documents for years before discovering defects: invalid wills, missing trusts, poorly worded no-contest clauses. Under Grant Thornton, if a beneficiary or executor learns of a misstep and connects it to legal advice or drafting, that may be enough to trigger the limitation period—even without obtaining a second opinion.

Example: A disappointed beneficiary is disinherited due to triggering a no-contest clause. They later learn their lawyer never explained the clause. That knowledge alone may start the clock, long before they engage new counsel.

2. Construction Deficiency Litigation

Latent construction defects often emerge gradually: leaky windows, shifting foundations, mold. Homeowners tend to delay legal action until they have an engineer’s report. Grant Thornton signals that once a homeowner sees evidence of damage and suspects a builder or subcontractor, the clock may already be ticking.

Example: Water damage appears near a new addition. The owner knows the name of the builder and the approximate date of work. If that knowledge allows a plausible inference of substandard work, the limitation period may have begun.

3. Real Estate Agent and Broker Liability

Misrepresentations during residential sales (e.g., about zoning, easements, renovations, or square footage) often give rise to claims against realtors or brokers. Grant Thornton will impact when the plaintiff is deemed to have discovered the claim.

Example: A buyer learns post-closing that a basement apartment is illegal. If municipal records contradict the agent’s pre-sale assurances, that discovery may suffice to infer negligence, starting the two-year window.

4. Insurance Broker Negligence

When brokers fail to procure proper coverage or misrepresent the scope of insurance, the insured may discover the problem only when a claim is denied. The denial itself, coupled with knowledge of the broker’s conduct, can trigger discoverability.

Example: A homeowner suffers a flood, but the claim is denied for lack of overland water coverage. The homeowner recalls asking the broker for “full flood protection.” That contradiction may be enough to start the clock.

5. Employment Law: Wrongful Dismissal and Layoff Advice

Employees often rely on faulty legal or HR advice when navigating terminations, layoffs, or resignations. They may not pursue claims until a subsequent employer or legal advisor flags an issue. But under Grant Thornton, the initial realization of harm and who caused it may be enough.

Example: An employee is wrongly told by HR that they’re not entitled to severance. They later read a government brochure contradicting this. That moment of realization may start the limitation clock against the employer or advisor.

6. Commercial Leasing and Property Disputes

Commercial tenants and landlords often litigate over misrepresented lease terms or ambiguous clauses. The discoverability threshold matters, particularly when tenants uncover discrepancies between oral promises and the lease.

Example: A tenant is told the lease includes signage rights, but the lease says otherwise. When the landlord refuses signage and the tenant rereads the contract, they may have sufficient knowledge to infer misrepresentation.

7. Professional Regulation and Discipline Proceedings

Regulated professionals (e.g., doctors, lawyers, engineers) may face civil actions for conduct already subject to discipline. If the complainant knows of the misconduct and that it caused harm, the civil clock likely starts then—not when the discipline ends.

Example: A client learns that a regulated immigration consultant submitted fraudulent paperwork, causing visa rejection. Even if the regulatory body takes a year to investigate, the limitation period may already be running.

8. Medical Malpractice and Delayed Diagnosis

Medical malpractice claims often involve delays in diagnosis or treatment. Plaintiffs may wait for second opinions. But Grant Thornton affirms that once a patient knows they were harmed and reasonably suspects the error, the clock starts.

Example: A patient discovers they have late-stage cancer after repeated reassurances that a lump was benign. If they learn that an earlier test was misread, and by whom, the window may already be open.

9. Tax and Financial Advisor Errors

Taxpayers may rely on accountants or financial advisors for filings, structuring, or investment decisions. If they suffer penalties or losses due to incorrect advice, the date they learn the advice was flawed may trigger discovery.

Example: A client is reassessed by CRA for a tax shelter their advisor recommended. Upon reviewing the reassessment notice, they realize the advice was likely wrong. That moment may be when the two-year period begins.

10. Municipal and Government Liability

Claims against municipalities or public authorities—for infrastructure failures, negligent inspections, or bylaw enforcement—often involve complex timelines. Grant Thornton clarifies that the limitation period starts when the plaintiff knows the harm and can connect it to the public body.

Example: A business floods due to poor storm drain maintenance. After learning the city knew of the drain blockage but failed to act, the business may be held to that knowledge as the start of its claim window.

IV. Practical Lessons for Litigators and Risk Managers

Grant Thornton is not just a limitation case—it’s a ticking time bomb in a lawyer’s file.

Litigators must revisit how they assess risk and advise clients. Delay is dangerous. Waiting for a complete file, a second expert, or more persuasive evidence may place the claim outside the limitation period.

For law firms, insurers, brokers, and other advisors, this case raises the stakes for early error recognition. Malpractice insurers may face earlier reporting obligations. Internal complaint systems must now consider whether the client could plausibly infer wrongdoing.

Risk management takeaway: Once the client knows the harm and who may be responsible, it’s likely time to document, diarize, and advise on limitation risk.

V. Conclusion: The End of the Waiting Game

Grant Thornton LLP v. New Brunswick is a recalibration of fairness and finality. It affirms that while plaintiffs don’t need full knowledge or legal certainty, they also don’t get to wait indefinitely for perfection. The standard is plausible inference—once the facts are enough to reasonably suspect negligence by a specific party, the two-year period begins.

In a post-Grant Thornton world, plaintiffs must act decisively. And lawyers must advise with sharper urgency. The limitation clock is no longer patient.