A promissory note is a written document in which one party formally promises to pay another a specific sum of money, either on demand or by a fixed date. Businesses use promissory notes to formalise short-term borrowing, and individuals use them when lending money to family members or friends. The document is simpler than a full loan agreement, but don't mistake that simplicity for weakness. A properly executed promissory note is enforceable in court.
What a promissory note actually contains
At its core, a promissory note records the deal between a borrower (the maker) and a lender (the payee). A valid note needs a few specific elements to hold up legally.
- The principal amount: the exact dollar figure being borrowed.
- The interest rate, if any, and how it compounds.
- The repayment schedule: a lump sum on a set date, or instalments over time.
- The names and signatures of both parties.
- The date the note is issued.
Some notes also include a default clause, which spells out what happens if the borrower misses a payment. Without one, the lender still has legal recourse, but enforcing the debt becomes slower and more expensive.
Promissory notes vs loan agreements
People often confuse promissory notes with loan agreements. Both document a debt, but a loan agreement is a two-sided contract that includes obligations for the lender too. A promissory note is a one-sided promise: the borrower commits to repay, and the lender signs to acknowledge receipt. That asymmetry makes promissory notes faster to draft and more commonly used for straightforward transactions.
If you're raising money through a startup, you've likely already encountered something adjacent: a convertible note, which starts as a promissory note but converts into equity rather than being repaid in cash. A standard promissory note doesn't convert. It's always repaid in money.
When businesses actually use them
Promissory notes appear in a wider range of situations than most people expect.
A supplier might accept a promissory note from a customer who can't pay immediately, treating it as a short-term credit arrangement. A property investor might sign one when borrowing bridging finance before a longer mortgage settles. A small business owner might use one to formalise a loan from a family member rather than running the money through the company as unstructured debt. In that last scenario, the note protects both sides: the lender has documentation of the debt, and the borrower can demonstrate the funds weren't a gift.
Promissory notes also appear in business acquisitions. When part of the purchase price is deferred, the seller often holds a promissory note from the buyer for the outstanding balance. This is sometimes called seller financing. Understanding how a business valuation works matters in those deals because the deferred amount is typically tied to an agreed figure for what the company is worth.
Secured vs unsecured promissory notes
A promissory note can be unsecured or secured against an asset. An unsecured note relies entirely on the borrower's promise to pay. If they default, the lender must pursue them through the courts to recover the money. A secured note attaches the debt to a specific asset, such as a vehicle, equipment, or property. If the borrower defaults, the lender can claim that asset instead of waiting on a court process.
Secured notes carry more paperwork, since the security interest usually needs to be registered. In Australia, personal property security interests are registered on the Personal Property Securities Register. Skipping that step leaves the lender exposed, particularly if the borrower becomes insolvent and other creditors have registered claims.
Negotiable promissory notes
Some promissory notes are negotiable instruments. That means the lender can sell or transfer the right to collect the debt to a third party. The borrower then owes money to whoever currently holds the note, not to the original lender. Bank bills and certain commercial paper work on this principle. Most private promissory notes between individuals or small businesses aren't negotiable, but the distinction is worth understanding if you're issuing a note in a more formal commercial context.
Common mistakes to avoid
The most frequent problem with promissory notes is vagueness. A note that says "John will repay Mary $10,000 when he can" isn't enforceable in any meaningful way. Set a specific repayment date or a clear schedule. State the interest rate, even if it's zero. Sign the document in front of a witness.
A second common mistake is failing to keep the note with the lender. The physical document (or a certified copy) is the evidence of the debt. Losing it complicates enforcement considerably. If the note is paid in full, the borrower should keep a signed receipt or written acknowledgment confirming the debt is discharged.
Finally, don't confuse a promissory note with a term sheet. A term sheet outlines the proposed terms of a deal but isn't usually binding in the same way. A promissory note IS the binding document.
Do you need a lawyer to write one?
For a straightforward loan between two private parties, a carefully written promissory note doesn't require a solicitor. Many template versions circulate online, and several are legally sound. That said, if the amount is large, if the borrower is a company rather than an individual, or if there's any secured interest involved, professional advice is worth the cost. A solicitor can also advise on stamp duty obligations, which vary by state and can apply to loan instruments above certain thresholds in some Australian jurisdictions.
The note itself is a tool. Like any tool, it works well when used correctly and causes problems when it's rushed or poorly constructed.