Suing on a Promissory Note in Ontario: What You Need to Prove

If you lent money and had the borrower sign a promissory note, you are in a considerably stronger legal position than someone relying on a verbal understanding or a string of text messages. A promissory note is a written, signed promise to pay a specific amount, and Ontario courts treat it as reliable evidence of the debt it describes. But "easier to prove" doesn't mean "automatic" — you still need to understand what makes a note enforceable and what a court will expect from you.

What Makes a Promissory Note Different From an IOU

An informal IOU is often just a casual acknowledgment — "I owe you this much" scrawled on paper or sent in a text, with few details beyond the amount. A promissory note, by contrast, is typically a more deliberate document that sets out:

• The amount owed
• The parties involved (who owes, who is owed)
• The terms of repayment — a lump sum, instalments, or on demand
• Whether interest applies, and at what rate
• The signature of the person making the promise to pay

The more clearly a note spells these terms out, the less room there is for the other side to dispute what was actually agreed. A vague, informal IOU still has legal weight, but it leaves more open to interpretation — and dispute — than a properly drafted note.

What You Need to Prove in Court

Suing on a promissory note generally requires you to establish:

1. The note exists and is genuine — that the signature is authentic and the document is what it claims to be
2. The terms of repayment — when and how repayment was due under the note's own terms
3. That repayment hasn't happened — or hasn't fully happened, if partial payments were made
4. The amount currently outstanding — including any interest specified in the note itself, if applicable

Because the note itself sets out most of these terms in writing, your case often turns less on competing memories of a conversation and more on straightforward proof: here is the signed document, here is what it required, and here is what hasn't been paid.

When the Note Is Disputed

Even a signed promissory note can be challenged. Common defences include claims that:

• The signature isn't genuine or wasn't properly witnessed
• The note was signed under pressure, fraud, or misrepresentation
• The debt was already repaid, in full or in part
• The terms were later modified by a separate agreement between the parties

If the borrower raises one of these defences, the dispute shifts from "does the note prove the debt" to a broader factual fight about how the note came to exist or what happened after it was signed. This is where solid supporting records — communications, payment history, and the circumstances of signing — become important again, even with a written note in hand.

Choosing the Right Court

The amount stated in the note (plus any interest and costs you're claiming) determines where you can sue. Claims within Small Claims Court's monetary jurisdiction can proceed there, using a simplified process designed for straightforward debt claims. Larger amounts require the Superior Court of Justice's ordinary civil process, or its Simplified Procedure track for mid-sized claims, both of which are more formal and generally warrant legal representation.

Practical Checklist Before You File

• [ ] Locate the original signed promissory note and make copies
• [ ] Confirm the exact repayment terms stated in the note — due date, instalments, interest, if any
• [ ] Calculate the current amount outstanding, accounting for any partial payments
• [ ] Gather any related communications about the loan or requests for repayment
• [ ] Send a written demand for payment referencing the note directly, with a firm deadline
• [ ] Confirm you are within the applicable limitation period before filing
• [ ] Determine whether Small Claims Court or Superior Court applies based on the amount

Frequently asked questions