Ontario Small Claims Court Defendant's Claim (Form 10A)

When You Need Form 10A

If someone sues you in Ontario Small Claims Court and you believe they owe you money from the same dispute, you don't put that in your Defence. Your Defence (Form 9A) responds to their claim. Your own monetary claim goes in a separate document: the Defendant's Claim (Form 10A).

Common scenarios:

• A contractor sues you for unpaid invoices, but you spent money hiring someone else to fix their defective work
• Your former landlord sues for property damage, but they never returned your last month's rent deposit
• A buyer sues over a used car sale, but they still owe you the balance of the purchase price

Form 10A can also name third parties who weren't part of the original lawsuit. If someone else is responsible for the damage the plaintiff is blaming on you, you can bring them into the case.

The 20-Day Deadline

Under Rule 10.01(2), you must file Form 10A within 20 days after filing your Defence (Form 9A). After that period, you may file it before trial or default judgment only with leave of the court.

That means the practical sequence is:

1. Get served with the Plaintiff's Claim (Form 7A)
2. File your Defence (Form 9A) within 20 days → fee: $77
3. File your Defendant's Claim (Form 10A) within 20 days after step 2 → fee: $108

Plan both filings from the start. If you know you have a counterclaim, draft Form 10A while you're preparing your Defence.

What Goes in Form 10A

Court file number and location: Same as the original claim — this ties your Defendant's Claim to the existing case.

Parties: List yourself as the "Defendant by Defendant's Claim" and the plaintiff as the "Defendant to the Defendant's Claim." If you're adding a new third party, include their full legal name and address.

Amount claimed: The specific dollar amount you're seeking, up to $50,000 (the Small Claims Court monetary limit as of O. Reg. 42/25). Interest and costs are calculated on top of this amount.

Reasons for claim: A clear factual statement explaining what happened and why the named parties owe you money. Same rules as any pleading: be specific, stick to facts, and reference documents you can produce as evidence.

Service and Filing

After filing Form 10A with the court clerk, you must serve it on:

• Every person against whom your Defendant's Claim is made. This may include the original plaintiff, a co-defendant, or a new third-party defendant.

New third-party defendants then have their own 20-day window to file a Defence to your Defendant's Claim.

The original Plaintiff's Claim and your Defendant's Claim are dealt with in the same action and generally at the same settlement conference. The Defendant's Claim is tried with the action unless the court orders otherwise.

Form 10A vs. Form 9A: Don't Mix Them Up

This is one of the most common procedural mistakes in Small Claims Court. Form 9A is your response to their allegations — why you don't owe what they say. Form 10A is your own claim for money. Putting your counterclaim inside Form 9A means the court can't act on it. If the 20-day Form 10A window expires, you need leave of the court to file later, and must do so before trial or default judgment.

If you're not sure whether your situation calls for a Defence alone or a Defence plus a Defendant's Claim, the deciding question is simple: are you saying "I don't owe them" (Form 9A only), or are you also saying "they owe me" (Form 9A plus Form 10A)?

Costs

• Form 10A filing fee: $108
• The trial-fixing fee ($308 for infrequent claimants) covers both the original claim and the Defendant's Claim — you don't pay it twice

The Ontario Small Claims Court Defence Guide includes worked examples for both defensive and counterclaim scenarios, with a step-by-step timeline showing how the two filings fit together.

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