When a partnership sours, the decision to sue a business partner in Ontario is rarely simple. You built something together, and now trust has broken down over money, control, or a betrayal you never saw coming. Litigation costs real money and takes real time, so you should understand what partnership law actually offers before you file anything. This guide walks through your rights as a partner, the duties your partner owes you, the remedies a court can order, and how to judge whether a lawsuit is the right move.
First, Confirm You Are Actually in a Partnership
Before you sue a business partner in Ontario, you need to know whether the law treats your business as a partnership at all. Section 2 of the Ontario Partnerships Act defines partnership as “the relation that subsists between persons carrying on a business in common with a view to profit.”
In other words, a partnership exists whenever two or more people carry on business in common with a view to profit, and no written agreement is required. That last point catches many people off guard. For example, you can be a partner without ever signing anything, simply because of how you and the other person actually ran the business. Conversely, sharing gross returns or owning property together does not by itself create a partnership, as section 3 makes clear.
If you incorporated instead, you are a shareholder rather than a partner, and a different statute governs. Disputes among shareholders fall under the Ontario Business Corporations Act, where the main tool is the oppression remedy under section 248 rather than partnership law. That route runs on its own tests and its own remedies, so if your business is incorporated, the rest of this guide will not be the law that governs your claim, and you should get advice specific to shareholder disputes.
Why the Distinction Changes Everything
The structure decides which duties apply, which remedies exist, and even who you sue. A partner sues under partnership law and equity, drawing on statutory duties to account and the court’s power to dissolve the firm. Those are genuinely different claims, and pleading the wrong one wastes time and money.
Therefore, a lawyer will examine both the legal documentation and how the business actually ran day to day. Who contributed capital, how the partners split profits, whether the business ever issued shares, and what the records show all bear on the question. Before you sue a business partner in Ontario, identifying the true structure is the first practical step, and it shapes everything that follows.
When There Is No Written Agreement
Many partner disputes that reach a courtroom involve no signed agreement, and the Act fills the gap with default rules. Section 24 sets the default rules governing partners’ interests, rights, and duties among themselves but “subject to any agreement express or implied between the partners,” so partners can contract out of any of it. Absent such an agreement, partners share capital and profits equally and bear losses equally; the firm indemnifies partners for liabilities incurred in the proper conduct of the business; every partner may take part in management, but none is entitled to a salary for doing so; no new partner may be admitted without unanimous consent; and ordinary matters go by majority, though the nature of the business cannot change without everyone’s agreement.
Some of those default rules catch people off guard. A partner who put in most of the money and did most of the work can discover that the law presumes an equal split and pays him nothing extra for his work.
Section 20 however permits partners to vary these rules “by the consent of all partners . . . express or inferred from a course of dealing,” which often makes proof of what was actually agreed upon a tricky issue. Courts can therefore infer the agreement from the conduct of the partners. The pattern and timing of draws, how the books recorded capital contributions and advances, who signed contracts and gave instructions to staff, how tax filings reported profits, and how the parties described themselves to banks, insurers, and clients all supply terms the parties never wrote down. Where the partners signed nothing, that documentary trail effectively becomes your partnership agreement.
The Fiduciary Duty Partners Owe Each Other
The Partnerships Act codifies three specific applications of the duty. Section 28 requires partners to render true accounts and full information of all things affecting the partnership to any partner or the partner’s legal representatives. Section 29 requires a partner to account to the firm for any benefit derived without consent from any transaction concerning the partnership or from any use by the partner of the partnership property, name, or business connection, and it extends to transactions undertaken after a partnership has been dissolved by a partner’s death but before its affairs have been wound up. Section 30 requires a partner who carries on a competing business of the same nature without consent to account for and pay over all profits made in that business.
However, these provisions do not represent an exhaustive list of a partner’s duties. Equity supplies the rest, including the obligations of loyalty, candor, and avoidance of any conflict between duty and self-interest.
The leading Ontario authority on this issue is Rochwerg v. Truster, 2002 CanLII 41715 (ON CA), 58 O.R. (3d) 687. The Court of Appeal described the foundation of the relationship in stark terms: “Mutual trust, confidence and good faith are the cornerstones of the modern professional services partnership.”
The court went on to confirm that these equitable principles still govern. It held that “the equitable principles developed over the last century concerning the fiduciary obligations of partners continue to control contemporary partnerships.” Partners owe loyalty, utmost good faith, and avoidance of conflict between duty and self-interest.
Two Statutory Duties You Can Sue On
The value of sections 28 and 29 lies in what they spare you from proving. A fiduciary claim at common law invites argument about the scope of the duty in the particular relationship. The statutory provisions bypass that.
Section 28 gives you a right to the books and records that does not depend on characterizing the relationship or establishing bad faith, and section 29 attaches to the benefit itself, so you need not show that the firm lost anything or that the partner acted dishonestly. The claim is complete once you prove the benefit, its connection to the partnership, and the absence of consent.
For instance, Rochwerg illustrates the point about competition. The partner’s directorships did nothing to harm the firm and took nothing away from it, yet the obligation to account still arose, because section 29 asks whether a benefit was derived without consent from a transaction concerning the partnership rather than whether the partner set himself against it. Section 30 covers the narrower case of an actual competing business and requires proof of the competition, which is why section 29 is usually the stronger claim to plead.
Consent is where these claims are won and lost. The Act requires consent to the benefit, not merely knowledge of the activity that produced it. Disclosing the role is not disclosing the benefit, and only the second satisfies the Act. That distinction decides most of these claims.
A partner who tells his partners about an outside directorship but says nothing about the shares attached to it has not obtained consent to keep them. Where the partnership has long operated informally, the defense will argue that acquiescence over a course of dealing supplied consent, and the documentary record will settle it.
What Counts as a Breach in Practice
In practice, a breach usually takes the shape of self-dealing. For instance, a partner might quietly divert a lucrative opportunity to a side company, skim secret profits, misuse partnership funds, take a hidden commission from a supplier, or set up a competing venture while still drawing partnership income.
Failing to share information is just as actionable, though people often overlook it. Cutting you off from the books, hiding a major contract, or concealing a benefit received through the firm’s connections can each breach sections 28 and 29 even where the partner insists the firm lost nothing.
Expulsion is another flashpoint. In Tim Ludwig Professional Corporation v. BDO Canada LLP, 2017 ONCA 292 (CanLII), the Court of Appeal upheld a substantial award to a partner forced out without the process his partnership agreement required. Because expulsion strips a partner of future profits, the court construed the expulsion clause strictly and read it in light of the duty of utmost good faith. (While a corporation is not a partnership, a corporation itself may become a member of a partnership.)
The Remedies Available When You Sue a Business Partner in Ontario
The remedies for a fiduciary breach are deliberately harsh, because the law wants to make disloyalty unprofitable. The primary remedy is an accounting and disgorgement, which strips the wrongdoer of profits earned through the breach whether or not you can prove a matching loss. A court may also impose a constructive trust over assets bought with diverted money, treating those assets as partnership property and giving you priority over the defaulting partner’s other creditors if he becomes insolvent. Where an asset has appreciated, the trust captures the increase, which a damages award would not.
Statutory and contractual remedies sit alongside the equitable ones. Section 28 compels production of accounts and information. Section 35 permits court-ordered dissolution where a partner’s conduct prejudicially affects the business or breaches the agreement.
Section 42 gives an outgoing partner an election between five percent interest on his share and the profits attributable to its use. Breach of a written agreement sounds in contract damages. Ludwig recovered expectation and aggravated damages for wrongful expulsion, over $1.3 million in all.
In addition, interim relief can preserve the eventual remedy. A court may appoint a receiver pending trial, enjoin dealings with partnership property, and order funds preserved. Where the wrongdoer holds the accounts and the books, speed matters more than the choice of final remedy.
This gain-based approach explains why fiduciary claims carry so much weight in partner disputes. A disloyal partner does not simply repay what you lost. He surrenders what he wrongfully gained, and as the numbers grow the difference between the two becomes the whole case.
Dissolution and the Court’s Power to Wind Up the Firm
Partnership law also offers an exit that corporate law reaches only with difficulty. If the partnership has no fixed term, section 32 lets a partner dissolve it simply by giving notice to the others, which ends the firm as of the date stated in the notice.
Where notice is unavailable or insufficient, section 35 empowers the court to dissolve the partnership on application by a partner. The listed grounds include a partner’s permanent incapacity, conduct prejudicial to the business, wilful or persistent breach of the partnership agreement, a business that can only be carried on at a loss, and a catch-all where circumstances make it just and equitable to dissolve.
Dissolution is the beginning of the unwind rather than the end of the fight. Section 38 preserves each partner’s authority so far as necessary to wind up the firm, and section 44 sets the order for distributing assets on a final settlement of accounts. Valuation, receivables, client lists, and goodwill usually attract the most contest.
Accounting Is Usually the Real Battleground
Partner litigation tends to turn less on dramatic allegations than on arithmetic. Once you establish a breach, the fight moves to tracing money, valuing the firm, and settling the accounts between partners, which is why the right to an accounting matters so much.
An accounting compels the other side to explain every dollar that moved through the business. Where one partner kept the records loosely or controlled them, a court can appoint a referee or an independent valuator to do the work, and the partner who kept the books opaque rarely benefits from that uncertainty. Anyone preparing to sue a business partner in Ontario should expect this stage to consume the most time and expense.
Watch Out for Joint Liability
Notably, partnership carries a risk that surprises people who assumed their business shielded them. Under sections 10 and 11 of the Partnerships Act, partners are jointly liable for the debts and obligations of the firm incurred while they are partners, and the firm is liable for a partner’s wrongful acts in the ordinary course of business.
Your partner’s misconduct can therefore expose you personally to third parties, even where you knew nothing about it. That exposure runs alongside your claim against the partner, so a dispute is rarely just about what you can recover. It is also about limiting what creditors and clients can recover from you.
What to Do Next and When to Call a Lawyer
If a partnership is breaking down, act deliberately rather than emotionally. Start by preserving everything: emails, texts, meeting notes, financial statements, bank records, and any written agreement you can find. Fiduciary and accounting claims turn on the factual history, so contemporaneous documents often decide the outcome.
Next, make a written demand for the books under section 28 rather than an informal request, because a documented refusal strengthens your position later. Then resist self-help measures like draining accounts, locking your partner out, or deregistering the business name. Your own conduct will face the same scrutiny as your partner’s, and a heavy-handed move can undermine an otherwise strong claim.
Most people who sue a business partner in Ontario call a litigator when the trust is truly gone, when money or opportunities flow somewhere they should not, or when someone pushes you out of a business you helped build. That said, not every dispute belongs in a courtroom. An early strategy session can clarify whether a demand letter, a negotiated buyout, a notice of dissolution, or a court application gives you the best path forward.
One more point deserves attention: limitation periods. Most civil claims in Ontario carry a two-year deadline under the Limitations Act, 2002 that starts once you knew, or ought to have known, about the wrongdoing. Delay can extinguish a strong claim without warning, so acting promptly protects both your evidence and your legal rights.
Conclusion
Deciding to sue a business partner in Ontario is a serious step, but you do not have to navigate it alone. No one enters a partnership expecting to end up in court, and when trust is gone, protecting your interests becomes the priority.
Ontario law hands anyone who must sue a business partner real tools, from the statutory duties to account and disclose, through disgorgement and constructive trust, to court-ordered dissolution. The right strategy depends on your structure, your evidence, and your goals. If your partnership is in trouble, the litigation team at Cowan can assess your situation and help you choose the approach that best protects what you have built. Reach out to discuss your options in confidence.
