- A court generally wants two things: proof that a loss happened, and a reasonable, documented basis for the amount you're claiming.
- Direct, out-of-pocket losses are usually the easiest to prove and the most persuasive to a court.
Winning on liability — convincing a court the other side actually breached the contract — is only half the battle. Ontario courts will not simply take your word for how much that breach cost you. Proving damages in a breach of contract claim means showing, with real evidence, both that you suffered a loss and roughly how much it amounts to.
Many otherwise strong claims underperform at trial or in settlement negotiations not because liability was unclear, but because the damages side was thin — vague estimates, missing receipts, or no explanation of how a number was calculated. This article walks through what kind of evidence actually supports a damages claim in Ontario, and where claims commonly fall short.
What a Court Actually Needs to See
A court generally wants two things: proof that a loss happened, and a reasonable, documented basis for the amount you're claiming. "I think I lost around this much" is not enough on its own — the more specific and supported your number is, the more a court can rely on it.
The type of evidence you need depends heavily on what kind of loss you're claiming. A lost sale looks different from a repair cost, which looks different from lost future income.
Types of Damages and the Evidence Behind Them
| Type of Loss | What Typically Supports It |
|---|---|
| Unpaid amounts owed under the contract | The contract itself, invoices, statements of account, proof of delivery or performance |
| Cost to fix or complete the work | Repair or completion quotes, receipts, before-and-after photos, comparison against the original contract price |
| Lost profit or lost business | Financial records, historical sales or revenue data, a clear (not speculative) link between the breach and the loss |
| Cost of a replacement (a substitute supplier, contractor, or product) | Invoices or quotes for the replacement, showing the price difference caused by the breach |
| Wasted expenses caused by relying on the contract | Receipts and records for the specific expenses, tied clearly to the contract in question |
Documenting Direct Financial Losses
Direct, out-of-pocket losses are usually the easiest to prove and the most persuasive to a court. Keep every invoice, receipt, bank statement, and payment record connected to the contract and the breach. Organize them chronologically so it's easy to follow the story: what was promised, what happened instead, and what it cost you.
If you had to pay someone else to finish or fix the work, get that new arrangement in writing too — a court will want to see that the replacement cost was reasonable, not inflated.
When Expert Evidence Helps
For more complex or specialized losses — construction defects, lost future profits, or valuing a business impact — an expert report can carry real weight. An expert can explain, in terms a court can rely on, how a loss was calculated and why the method used is reasonable.
Expert evidence is not required for every claim, and it adds cost, so it makes the most sense for larger or more technical disputes where a bare document trail won't be enough on its own.
Your Mitigation Efforts Matter Too
Ontario courts generally expect a party claiming damages to have taken reasonable steps to limit their own losses. That means documenting what you did to mitigate — quotes obtained, replacement arrangements made, efforts to find alternative options — not just the losses themselves.
Evidence that you acted reasonably to reduce the damage strengthens your claim; evidence (or an absence of evidence) suggesting you let losses pile up unnecessarily can reduce what a court is willing to award.
Why Damages Claims Fall Apart
- No documentation, just an estimate. A number without receipts, invoices, or records behind it is hard for a court to accept.
- Loss not clearly tied to the breach. If the connection between what went wrong and what it cost you is speculative, a court may discount or reject it.
- No mitigation evidence. Silence on what you did to limit your losses invites the argument that you didn't try.
- Inflated or padded figures. Overreaching on the number can undermine the credibility of the parts of your claim that are genuinely solid.
Frequently asked questions
Do I need receipts for everything, or will an estimate work?
Receipts, invoices, and other records are always stronger than an estimate. Where you genuinely can't produce a document — for example, an informal cash arrangement — be prepared to explain why and support the figure with whatever secondary evidence exists.
How far back should my financial records go?
Generally, far enough to show a clear "before and after" picture connected to the breach — historical figures that establish what would have happened without the breach, and current figures showing the actual impact.
Is a lawyer's letter enough proof of my losses?
No. A demand letter sets out your position, but it is not evidence of the underlying loss on its own — the court will still want the invoices, contracts, and records the letter is based on.
What if my losses are hard to put an exact number on?
Some losses genuinely are harder to quantify precisely, and courts recognize that. The goal is a reasonable, well-supported estimate backed by the best available evidence — not false precision.
This is a litigation question
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