Can You Sue Your Lawyer, Realtor, or Accountant in Ontario? Professional Negligence Explained
In Ontario, you can sue a lawyer, realtor, accountant, or other professional for negligence when their work falls below the standard of a reasonably competent professional and that failure causes you a financial loss. To succeed, you must prove four things: a duty of care, a breach of that duty, that the breach caused your loss, and the amount of that loss. These claims typically require expert evidence from another professional in the same field confirming the standard was not met. A regulatory complaint — to a body such as the Law Society of Ontario, the Real Estate Council of Ontario, or CPA Ontario — can lead to discipline but does not award you compensation; only a civil claim can do that. Most professional negligence claims must be started within two years under the Limitations Act, 2002, and that clock often runs from the date you discovered the loss, not the date of the mistake.
When a Trusted Professional's Mistake Costs You Money
You hired a professional you trusted and paid for their expertise. Of course, you expected the job to be done properly. Unfortunately, something went wrong. A deadline slipped, a form was filed incorrectly, or advice turned out to be flatly wrong, and now it has cost you real money. It is a frustrating, unsettling position, and many Ontarians find themselves in this situation every year.
The reassuring part is that you have options, and understanding them is the first step to feeling back in control. Ontario law recognizes that professionals owe their clients a duty to work competently, and when they fall short in a way that causes harm, there may be a path to compensation.
This guide explains what professional negligence is, what you would need to prove, how the deadlines work, and how a complaint differs from a lawsuit.
Quick Start: Which Professional Let You Down?
Whichever applies to you, our civil litigation team can help you weigh a complaint, a claim, or both.
What Professional Negligence Means in Ontario
The “standard of care” is the level of skill and care that a reasonably competent professional in that field would typically bring to the same task. It is measured against capable peers, not against perfection.
This distinction matters, because not every disappointing outcome is negligence. A professional can make a judgment call that later proves wrong and still have acted within the range of reasonable practice. Losing a case, a deal falling through, or a tax position the Canada Revenue Agency (CRA) later challenges does not, on its own, mean the professional was negligent.
The Four Elements You Must Prove
A duty of care is a legal responsibility to act carefully toward someone. When you retain a professional, and they agree to act for you, that relationship typically creates a duty of care to you.
A breach of the standard means the professional did something a reasonably competent peer would not have done, or failed to do something a reasonably competent peer would have done, such as missing a filing deadline or overlooking a known risk.
Causation links the breach to your loss. You typically must show the loss would not have happened without the professional's error. In a claim against a lawyer, that can mean showing you would likely have had a better result if not for the professional's error.
Damages are the actual, provable loss you suffered, such as money lost, extra costs to fix the problem, or an opportunity that can be valued in dollars.
| Element | What it means | Everyday example |
|---|---|---|
| Duty of care | A legal responsibility to act carefully toward you, created when a professional agrees to act for you. | A lawyer you retain to close your home purchase owes you a duty of care. |
| Breach of the standard | Doing something a reasonably competent peer would not have done, or failing to do what they would. | Missing a court filing deadline, or overlooking a known title problem. |
| Causation | Showing the loss would not have happened without the professional's error. | You would likely have kept a right or a deal if the deadline had been met. |
| Damages (provable loss) | The actual, measurable loss you suffered, valued in dollars. | Money lost, penalties, or the extra cost to fix the problem. |
Regulatory Complaint Versus Civil Lawsuit: What Each One Can Do
When you file a complaint, the regulator investigates whether the professional broke its rules of conduct. The goal is protecting the public, not compensating you. The regulator does not represent you, and even a finding against the professional typically does not award you damages. Timelines and processes vary by regulator, and each has its own way of handling and reporting complaints.
A civil lawsuit works the other way. You, through your lawyer, bring the claim in court, and the goal is compensation for the loss you can prove. The two routes are not mutually exclusive. You can often pursue both at the same time, and a complaint may run alongside a claim without replacing it.
| Regulatory complaint | Civil lawsuit | |
|---|---|---|
| Where you go | The professional's regulator (LSO, RECO, CPA Ontario, or FSRA). | The Superior Court of Justice, or the Small Claims Court. |
| What it can do | Discipline the professional — a warning, a fine, or a licence suspension. | Award compensation for a loss you can prove. |
| What it cannot do | Pay you compensation. | Discipline a professional or change their licence. |
| Typical goal | Protect the public. | Recover your money. |
Why Expert Evidence Usually Matters
One feature sets professional negligence apart from many other claims: you usually need expert evidence. Expert evidence is an opinion from another qualified professional in the same field, explaining what a reasonably competent professional would have done and how the person you are suing fell short.
A judge is not expected to know, without help, what careful practice looks like inside a specialized field. Therefore, in most professional negligence cases, an independent expert reviews the file and gives an opinion on the standard of care. Without that opinion, a claim can be hard to prove, which is part of why these cases are demanding.
There are narrow situations where an error is so obvious that expert evidence may not be required, but they are the exception. Planning for an expert opinion early is often one of the most practical steps in building a claim.
The Two-Year Clock and the Discoverability Twist
A “limitation period” is the legal deadline to start a court case. Ontario's basic limitation period is two years, set out in the Limitations Act, 2002.
“Discoverability” means the clock can start later than the mistake itself, on the day you first knew, or reasonably ought to have known, that you suffered a loss, that it was connected to the professional, and that a claim was an appropriate response. Because a professional's error can stay hidden for months or years, the discovery date is frequently later than the error date.
There is also an “ultimate limitation period” of 15 years that can bar a claim regardless of when it was discovered. Deadlines in this area are strict and fact-specific. So, if timing is a concern, it is worth having Ontario's two-year limitation period assessed promptly.
How a Professional Negligence Claim Typically Unfolds
Every file is different, but a professional negligence claim in Ontario often moves through the same general stages:
- 1Gather your records.Collect your retainer or engagement documents, emails, invoices, and anything showing what the professional was asked to do and what happened.
- 2Get independent legal advice.A litigation lawyer who did not handle the original matter can review whether the four elements may be present.
- 3Obtain an expert opinion.An expert in the professional's field can assess whether the standard of care was met.
- 4Send a demand and notify the insurer.Many professionals carry liability insurance, and a formal demand letter often opens the door to negotiation before court.
- 5Issue the claim.If the matter does not resolve, a court claim starts the formal process.
- 6Identify the right court.The size of the claim decides where it is heard.
For comparison, the process of suing a contractor for bad work follows similar steps, and smaller claims may proceed through the Small Claims Court.
| Claim value | Court | Note |
|---|---|---|
| $50,000 or less | Small Claims Court | The monetary limit rose to $50,000 on October 1, 2025. |
| More than $50,000 | Superior Court of Justice | Larger claims proceed here. |
Common Mistakes That Can Sink a Claim
A few avoidable mistakes come up again and again:
Frequently Asked Questions
Can I sue my lawyer if I lost my case?
What is the difference between complaining to the Law Society and suing my lawyer?
Can I sue my real estate agent for giving me bad advice?
My accountant made a tax error that cost me money, can I sue?
How long do I have to sue a professional for negligence in Ontario?
Do I really need an expert to prove the professional was negligent?
How much does it cost to bring a professional negligence claim?
What happens if the professional has retired, moved, or closed their practice?
Talk to a Litigation Lawyer Before the Clock Runs Out
Being let down by a professional you trusted is stressful, but you are not without options. In Ontario, professional negligence claims come down to four questions, namely duty, breach, causation, and loss, and they usually call for expert evidence and careful attention to a strict two-year deadline. A regulatory complaint and a civil claim are separate tools, and you can often use both.
If you think a professional's mistake has cost you money, the most practical step is an early, honest assessment of your situation. Qasim Ali, Principal Lawyer at Nihang Law and the firm's litigation team act for individuals and small businesses across Toronto, Scarborough, and the wider GTA.
Talk It Through With Our Litigation Team
If a professional's mistake has cost you money, an early assessment of your options and the deadlines that may apply is the most practical first step.
Contact Nihang Law
About the author
Qasim Ali
Principal Lawyer · Nihang Law Professional Corporation · Toronto & Scarborough, Ontario · Law Society of Ontario
Qasim Ali is the Principal Lawyer at Nihang Law Professional Corporation, serving clients across Toronto, Scarborough, and the broader Greater Toronto Area. He provides full-service legal representation across immigration, real estate, family law, criminal law, civil litigation, employment law, wills and estates, and business law.
Nihang Law is particularly recognized for its depth in immigration and real estate law — a combination that serves newcomers and growing families navigating both legal systems simultaneously.
Learn more about Qasim Ali →Sources & References
- Limitations Act, 2002, S.O. 2002, c. 24, Sch. B — basic two-year period (s. 4), discoverability (s. 5), ultimate 15-year limit (s. 15). Government of Ontario: https://www.ontario.ca/laws/statute/02l24
- Small Claims Court monetary limit of $50,000 (effective October 1, 2025). Government of Ontario: https://www.ontario.ca/page/suing-someone-small-claims-court
- Complaints about a lawyer or paralegal. Law Society of Ontario: https://lso.ca/public-resources/complaints
- Complaints about a real estate agent. Real Estate Council of Ontario: https://www.reco.on.ca
- Complaints about an accountant. CPA Ontario: https://www.cpaontario.ca
- Complaints about a mortgage broker. Financial Services Regulatory Authority of Ontario: https://www.fsrao.ca
- Canada Revenue Agency. Government of Canada: https://www.canada.ca/en/revenue-agency.html
- The duty, breach, causation, and damages framework for negligence is established at common law in Ontario.