- A third party claim lets a defendant — the person being sued — add another person or company to the same court case, asserting that the third party is responsible, in whole or in part,…
- Common situations include: - A general contractor is sued over a defect, but the actual work was done by a subcontractor - A retailer is sued over a faulty product, but the manufacturer…
- Identify the right party — the person or business you believe bears some or all of the responsibility.
Sometimes the person suing you has picked the wrong — or at least not the only — target. If someone else caused, contributed to, or should share responsibility for the loss the plaintiff is claiming, Ontario's Small Claims Court has a way to bring that person or business directly into the existing lawsuit rather than fighting the whole claim alone. This is a third party claim small claims court ontario proceeding.
What a Third Party Claim Is
A third party claim lets a defendant — the person being sued — add another person or company to the same court case, asserting that the third party is responsible, in whole or in part, for the loss the plaintiff is claiming. Instead of paying the plaintiff and then trying to recover from the real culprit separately, you can pull everyone into one proceeding.
When to Consider a Third Party Claim
Common situations include:
- A general contractor is sued over a defect, but the actual work was done by a subcontractor
- A retailer is sued over a faulty product, but the manufacturer or supplier is really responsible
- Two parties allegedly contributed to a loss, and you believe responsibility should be shared
The core argument is usually some version of "if I'm liable to the plaintiff at all, this other person should have to pay some or all of it, because they're the one who actually caused the problem."
How to Start a Third Party Claim
- Identify the right party — the person or business you believe bears some or all of the responsibility.
- Prepare a third party claim document explaining the connection between the original claim and the third party's alleged responsibility.
- File it with the same Small Claims Court handling the original lawsuit.
- Serve the third party, giving them formal notice of the claim against them and an opportunity to respond.
- The court manages the case together, generally scheduling the settlement conference (and trial, if needed) to cover the original claim and the third party claim at the same time.
What the Third Party Can Do in Response
Once served, the third party has options similar to an original defendant: they can defend the claim against them, or they can do nothing — in which case the same default process that applies to any other Small Claims Court defendant can apply to them too, potentially leaving them bound by the outcome without having participated.
Third Party Claim vs. Suing Them Separately
| Consideration | Third Party Claim (Same Case) | Separate Lawsuit Later |
|---|---|---|
| Number of proceedings | One combined case | Two separate cases, potentially years apart |
| Risk of inconsistent findings | Lower — one judge hears everyone | Higher — different judges could reach different conclusions |
| Cost and time | Generally more efficient | Often duplicated effort and expense |
| Timing of recovery | Resolved alongside the main claim | Delayed until a second lawsuit concludes |
For most situations where responsibility is genuinely shared or disputed, resolving everything together tends to be more efficient than starting from scratch later.
Practical Considerations Before You Add a Third Party
- [ ] Make sure you have a genuine legal basis connecting the third party to the plaintiff's loss — not just frustration at who else was involved
- [ ] Consider whether adding a third party will meaningfully delay resolving the main claim
- [ ] Factor in the modest additional court fee and paperwork involved in filing and serving a third party claim
- [ ] Think about whether the third party is realistically able to pay if you succeed against them
- [ ] Weigh whether the added complexity might tip the case beyond what makes sense to handle without a lawyer or paralegal
Frequently asked questions
Can I bring a third party claim after the settlement conference has already happened?
It's possible in some circumstances, but it's considerably easier and cleaner to raise it as early as possible — ideally alongside or shortly after filing your defence — rather than later in the process.
What if the third party doesn't respond to the claim against them?
The same kind of default process that applies to an unresponsive defendant in the original claim can apply to an unresponsive third party, potentially leaving them bound by the court's decision even without participating.
Does adding a third party change the monetary limit of the case?
The overall Small Claims Court monetary jurisdiction still applies to the case as a whole. If the combined claims would exceed that limit, the matter may not be able to proceed entirely within Small Claims Court.
Can the plaintiff object to me adding a third party?
The plaintiff doesn't control whether you can add a third party, but the court retains overall discretion to manage how the case proceeds, including timing, if adding a third party would cause real unfairness or delay.
This is a litigation question
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