A promise to pay contract is legally binding when four things are true: both sides genuinely agree to the same terms, each side gives up something of value, both signers have the legal capacity to contract, and the purpose is lawful. Beyond those legal essentials, the document itself needs to state the loan amount, the interest rate, the repayment schedule, what happens on default, and any collateral securing the debt. Get those pieces right and a court will enforce it. Skip one, and the entire agreement can collapse.
The Four Elements That Make It Enforceable
Every enforceable promise to pay rests on the same four pillars from general contract law.
Mutual Assent
Both parties have to agree to the same terms. One side makes a clear offer; the other accepts it without conditions or material changes.1Legal Information Institute. Mutual Assent If the borrower believes the interest rate is 5% and the lender believes it is 8%, there is no meeting of the minds and nothing for a court to enforce. The signed document is the strongest evidence that both sides understood and accepted every term.
Consideration
Each party must give up something of value. The lender’s consideration is the money handed over; the borrower’s is the promise to repay, usually with interest. A bare promise to pay someone without receiving anything in return can be treated as an unenforceable gift rather than a contract.
Capacity
Both signers need the legal ability to contract. That generally means being of legal age and mentally competent to understand the obligation. Contracts signed by minors or by people who cannot grasp what they are agreeing to are typically voidable under state law.
Legality
The loan’s purpose cannot be illegal, and the interest rate cannot exceed the state’s usury cap. Every state sets its own ceiling on private-lender interest, and charging above that ceiling is usury.2Legal Information Institute. Usury Consequences vary: some states void only the excess interest, others void the entire debt or impose penalties on the lender. Federal law preempts state interest-rate caps on first-lien residential mortgage loans.3eCFR. 12 CFR Part 190 – Preemption of State Usury Laws
Why the Agreement Belongs in Writing
Oral loan agreements are enforceable in some situations, but relying on one is a mistake. Every state has adopted some version of the Statute of Frauds, which requires certain contracts to be in writing. Any contract that cannot be performed within one year of the date it was made falls within the rule, so any loan with a repayment period longer than a year should always be signed and on paper. Some states also require a suretyship promise (a third party guaranteeing someone else’s debt) to be in writing.
Even for shorter loans that might slip past the Statute of Frauds, a written agreement removes the your-word-against-mine problem. Judges enforce clear written terms far more readily than they reconstruct handshake deals.
Terms the Document Should Contain
The four legal elements make the contract binding; the financial terms below make it usable. Missing or vague terms will not always void the contract, but they invite disputes that are expensive to resolve.
Principal Amount
State the exact dollar figure the borrower receives and agrees to repay. The standard Fannie Mae/Freddie Mac promissory note used nationwide opens with the borrower’s promise to repay a specific principal.4Consumer Financial Protection Bureau. Multistate Fixed Rate Note – Single Family – Fannie Mae/Freddie Mac Uniform Instrument Write the amount in both numerals and words to eliminate ambiguity.
Interest Rate
Say whether the rate is fixed or variable. A fixed rate stays put for the life of the loan. A variable rate should be tied to a published benchmark such as the prime rate, plus a stated margin, so future adjustments are not up for debate. Leave the interest rate out entirely and most states will impose a default statutory rate that may be higher or lower than either side expected.
Repayment Schedule
Spell out how often payments are due (monthly, quarterly, biweekly), the exact calendar date of each, and the total number of payments. A precise schedule makes it obvious when a payment is late.
Late Payment Penalties
The uniform promissory note allows the lender to charge a late fee calculated as a percentage of the overdue payment of principal and interest, triggered after a specified number of calendar days past the due date.4Consumer Financial Protection Bureau. Multistate Fixed Rate Note – Single Family – Fannie Mae/Freddie Mac Uniform Instrument Whatever number you pick needs to be commercially reasonable. States regulate maximum late fees, and an excessive penalty can be struck down.
Default and Acceleration
The default clause defines what counts as a breach: a missed payment, a bankruptcy filing, or a violation of another term. The acceleration clause is the powerful one. It lets the lender declare the entire remaining balance due immediately after a default. Under the standard uniform note, the lender must first send written notice giving the borrower at least 30 days to cure before accelerating.4Consumer Financial Protection Bureau. Multistate Fixed Rate Note – Single Family – Fannie Mae/Freddie Mac Uniform Instrument Private notes are not required to follow that model. Some waive the notice requirement and make acceleration automatic on default.
Collateral
If the loan is secured, the agreement must identify the specific property pledged against the debt. Collateral turns an unsecured promise into a secured obligation, giving the lender the right to seize that property if the borrower defaults. This distinction matters enormously when it is time to collect.
Signing, Notarization, and Electronic Signatures
The contract is not enforceable until it is properly signed. Both parties should sign and date the document.
Notarization is not required for a promissory note in most states. It still adds real protection, because the notary verifies each signer’s identity, which makes it much harder for someone to later claim the signature is not theirs. When the amount justifies the modest cost, notarization is worth doing.
Electronic signatures are legally valid. Under the federal Electronic Signatures in Global and National Commerce Act, a contract or signature cannot be denied legal effect solely because it is in electronic form.5Office of the Law Revision Counsel. 15 USC 7001 – General Rule of Validity A promissory note signed through a platform like DocuSign carries the same legal weight as pen-on-paper, provided both parties consent to conducting the transaction electronically and the platform keeps a reliable audit trail.
Tax Rules for Private Lenders
This is where private lenders often get surprised. The IRS cares about interest on private loans, including loans between family members or friends, and ignoring the rules can create an unexpected tax bill.
Any interest you receive as a lender is taxable income. You must report it on your federal return even if you never receive a Form 1099-INT.6Internal Revenue Service. Topic no. 403, Interest Received A business that pays $600 or more in interest to an individual lender is required to issue that lender a 1099-INT.
Now the trap. If you lend money at an interest rate below the IRS’s Applicable Federal Rate (AFR), the IRS treats the forgone interest (the gap between the AFR and what you actually charged) as if the lender transferred it to the borrower as a gift and the borrower paid it back as interest.7Office of the Law Revision Counsel. 26 USC 7872 – Treatment of Loans With Below-Market Interest Rates The lender ends up owing income tax on interest they never actually received, and the transaction may count against the lender’s lifetime gift tax exclusion.
There is a $10,000 exception: the imputed interest rules do not apply to gift loans between individuals as long as the total outstanding balance between them stays at or below $10,000.7Office of the Law Revision Counsel. 26 USC 7872 – Treatment of Loans With Below-Market Interest Rates Above that threshold, charge at least the AFR. For April 2026, the AFR ranges from 3.59% for short-term loans of three years or less to 4.62% for long-term loans over nine years.8Internal Revenue Service. Revenue Ruling 2026-7 – Applicable Federal Rates for April 2026 The IRS publishes updated rates monthly.
What to Do If the Borrower Doesn’t Pay
A well-drafted contract gives the lender a roadmap for recovery. The process usually moves through stages, and skipping steps can weaken the legal position.
Send a Demand Letter
Start with a formal written demand. The letter should notify the borrower they are in default, identify the specific terms violated, state the total amount due (including any accelerated balance), and set a deadline to pay. Even when the contract does not require it, sending a demand letter creates a paper trail courts look on favorably and gives the borrower one last chance to resolve the matter before litigation costs mount.
File Suit and Get a Judgment
If the demand does not produce payment, the lender files a lawsuit. Smaller amounts often belong in small claims court, though dollar limits vary widely by state. Larger debts go to civil court. The goal is a court judgment, an order confirming the debt amount and the lender’s right to collect. Without a judgment, an unsecured lender’s collection tools are extremely limited.
Collect on the Judgment
A judgment unlocks several enforcement tools. Wage garnishment redirects part of the borrower’s paycheck. Federal law caps this at 25% of disposable earnings, or the amount by which weekly disposable earnings exceed 30 times the federal minimum wage, whichever is less.9Office of the Law Revision Counsel. 15 USC 1673 – Restriction on Garnishment A bank levy lets the lender seize funds from the borrower’s deposit accounts up to the judgment amount. A lien on real estate blocks the borrower from selling or refinancing until the judgment is satisfied.
Secured Debt Is Faster
When the loan is backed by collateral, the lender often does not need the full lawsuit-and-judgment process. Under the Uniform Commercial Code, a secured party may take possession of collateral after default without going to court, so long as the repossession happens without a breach of the peace.10Legal Information Institute. UCC 9-609 – Secured Party’s Right to Take Possession After Default This is why an auto lender can send a tow truck to your driveway. If there is any confrontation or resistance, the secured party must stop and pursue judicial remedies instead.
If the Borrower Files for Bankruptcy
Bankruptcy is the scenario every private lender should think about before signing. Most unsecured private promissory notes are dischargeable in a Chapter 7 bankruptcy, meaning the borrower’s obligation is wiped out and the lender collects nothing.
There are exceptions. If the borrower obtained the loan through fraud, a false financial statement, or false pretenses, the debt survives bankruptcy.11Office of the Law Revision Counsel. 11 USC 523 – Exceptions to Discharge Debts arising from embezzlement, larceny, or willful and malicious injury to the lender’s property also survive. For a straightforward loan where the borrower simply ran out of money, though, the lender is generally out of luck once a discharge is granted.
This is exactly why collateral matters so much. A properly secured loan gives the lender a claim on specific property that survives independently of the borrower’s personal liability. A secured creditor’s lien on collateral continues through bankruptcy, so the borrower typically has to either keep paying or surrender the property. When you are lending a significant sum to someone whose creditworthiness is uncertain, requiring collateral is not being harsh. It is being realistic about the risk.