You're lending money to someone. Maybe it's a friend, family member, or business contact. You want documentation—but should you use an IOU or a promissory note?
The short answer: a promissory note offers much stronger legal protection. Here's why, and when each document makes sense.
Key Takeaways
- IOUs are informal acknowledgments of debt with minimal legal enforceability
- Promissory notes are legally binding contracts with specific repayment terms
- Promissory notes can be enforced in court; IOUs often cannot
- For any significant loan ($500+), use a promissory note
- Both should be signed and witnessed for best protection
What Is an IOU?
An IOU ("I owe you") is a simple written acknowledgment that a debt exists. It's informal and often looks like this:
IOU
I, John Smith, owe Jane Doe $500.
Signed: _________________
John Smith
Date: March 15, 2026
Characteristics of an IOU:
- Informal — No specific format required
- Brief — Often just one or two sentences
- Acknowledges debt exists — But doesn't specify repayment terms
- May not be legally enforceable — Depends on jurisdiction and content
When an IOU Might Suffice:
- Small amounts between trusted parties (under $100)
- Short-term loans (paid back within days)
- Situations where you just want a written record, not legal protection
- When the borrower would be offended by a formal contract
IOUs have limited legal value
An IOU proves a debt exists, but it doesn't prove when or how it should be repaid. If the borrower refuses to pay, an IOU may not be enough to win in court—especially if they claim it was a gift or that repayment terms were different.
What Is a Promissory Note?
A promissory note is a formal, legally binding contract in which the borrower promises to repay a specific sum under specific terms.
PROMISSORY NOTE
Principal Amount: $5,000.00
Date: March 15, 2026
FOR VALUE RECEIVED, John Smith promises to pay to Jane Doe the principal sum of Five Thousand Dollars ($5,000.00), plus interest at the rate of 5% per annum.
Payment Terms:
- Monthly payments of $443.21
- First payment due: April 15, 2026
- Final payment due: March 15, 2027
- Payments to be made via: Bank transfer / Check / Venmo
Late Fee: $50 if payment is more than 15 days late
Default: If Borrower fails to make payment within 30 days of due date, the full remaining balance becomes immediately due.
Borrower: _________________
John Smith
Address: 123 Main St, Anytown, ST 12345
Witness: _________________
Date: _________________
[Notary section, if applicable]
Characteristics of a Promissory Note:
- Legally binding — Enforceable in court
- Specific terms — Amount, interest rate, payment schedule, due dates
- Includes consequences — Late fees, default provisions, acceleration clauses
- Can be secured or unsecured — May include collateral
- May be notarized — Adds extra legal weight
Key Differences: IOU vs. Promissory Note
| Feature | IOU | Promissory Note |
|---|---|---|
| Legal enforceability | Limited | Fully enforceable |
| Repayment terms | Often unspecified | Detailed and specific |
| Interest rate | Rarely included | Typically specified |
| Payment schedule | Rarely included | Required |
| Late fees/penalties | No | Yes |
| Default provisions | No | Yes |
| Collateral/security | No | Can include |
| Notarization | No | Optional but recommended |
| Best for amounts | Under $100 | $100+ |
When to Use a Promissory Note
Use a promissory note whenever:
- Amount is $500 or more — Worth the paperwork to protect yourself
- Repayment will take time — Anything beyond a few weeks
- Interest is being charged — Must be documented
- It's a business transaction — Always use formal documentation
- You want legal recourse — Promissory notes hold up in court
Essential Elements of a Valid Promissory Note
For a promissory note to be legally enforceable, it must include:
- Names and addresses — Of both borrower and lender
- Principal amount — The amount being borrowed
- Interest rate — If applicable (must comply with usury laws)
- Repayment terms — How and when payment will be made
- Due date(s) — Specific dates for payment
- Signature of borrower — Essential for enforceability
- Date of signing — When the note was executed
Recommended additions:
- Witness signature(s)
- Notarization
- Late fee provisions
- Default and acceleration clauses
- Prepayment terms (can borrower pay early without penalty?)
- Choice of law (which state's laws govern the note)
- Attorney fees clause (borrower pays legal costs if they default)
Usury laws matter
Every state has maximum interest rates (usury laws) for private loans. Charging above the legal rate can make your note unenforceable—and in some states, illegal. Check your state's limits before setting an interest rate. Typical range: 6-12% for personal loans.
Secured vs. Unsecured Promissory Notes
Unsecured Promissory Note
No collateral backs the loan. If the borrower defaults, you must sue to collect. Most personal loans are unsecured.
Secured Promissory Note
The borrower pledges collateral (car, property, equipment). If they default, you can take the collateral. More protection for the lender.
SECURITY COLLATERAL
This Promissory Note is secured by the following collateral:
- 2022 Honda Civic, VIN: 1HGCX123456789012
In the event of default, the Lender has the right to take possession of the collateral and sell it to satisfy the outstanding debt. Any surplus after satisfying the debt shall be returned to the Borrower.
What Happens If Borrower Doesn't Pay?
With an IOU:
- You may not be able to enforce it in court
- Borrower can claim it was a gift, or dispute terms
- Small claims court may or may not accept it as evidence
With a Promissory Note:
- Send demand letter — Formal notice of default
- File in small claims or civil court — Depending on amount
- Present the note as evidence — It's a binding contract
- Get a judgment — Court orders payment
- Collect the judgment — Wage garnishment, bank levy, or seizure of collateral (if secured)
Free Promissory Note Template
Use this template as a starting point for your loan:
PROMISSORY NOTE
Principal Amount: $[AMOUNT]
Date: [DATE]
State: [STATE]
FOR VALUE RECEIVED, [BORROWER NAME] promises to pay to [LENDER NAME] the principal sum of $[AMOUNT], plus interest at the rate of [X]% per annum.
1. PAYMENT TERMS
[Choose one:]
□ Lump sum payment of $[AMOUNT] due on [DATE]
□ Installment payments of $[AMOUNT] due on [DAY] of each month, beginning [DATE] and continuing until paid in full
2. LATE FEE
Payments not received within [X] days of due date will incur a late fee of $[AMOUNT].
3. DEFAULT
If Borrower fails to make payment within [X] days of due date, the full remaining balance becomes immediately due at Lender's option.
4. PREPAYMENT
Borrower [may / may not] prepay this note without penalty.
5. ATTORNEY FEES
If Borrower defaults, Borrower agrees to pay reasonable attorney fees and court costs incurred by Lender in collecting this debt.
6. GOVERNING LAW
This Note shall be governed by the laws of the State of [STATE].
BORROWER:
_______________________
[Borrower Name]
Address: _________________
_______________________
LENDER:
_______________________
[Lender Name]
Address: _________________
_______________________
WITNESS (Optional):
_______________________
[Witness Name]
Date: _________________
[NOTARY SECTION - Optional but Recommended]
State of _______________
County of _____________
Subscribed and sworn to before me this ____ day of __________, 20__.
_______________________
Notary Public
Related Tools
- How to Write a Formal Demand Letter — For when borrower defaults
- Do I Need a Lawyer to Collect a Debt? — When to DIY vs. hire
- Can You Go to Jail for Not Paying Debt? — Criminal vs. civil debt