An interest-only promissory note is a written loan agreement in which your scheduled payments cover only the interest for a set period, leaving the original principal untouched until later. You get lower payments early on and a much larger obligation when principal repayment starts. The structure shows up most often in commercial real estate, bridge lending, and private loans between family members or business associates, where short-term cash flow matters more than steady paydown.
How the Payments Are Calculated
The math is simple. Multiply the outstanding principal by the annual interest rate, then divide by twelve. On a $500,000 note at 6%, the monthly payment is $2,500. All of it goes to the lender as compensation for the use of the money, and none of it reduces the balance.1Bankrate. Interest Only Mortgage Calculator
The interest-only period typically runs three to ten years, depending on what the parties negotiate.2Chase. Interest-Only vs Traditional Mortgage Throughout that stretch, the principal stays frozen at the original amount borrowed. That is the fundamental difference from a standard amortizing loan, where every payment chips away at both interest and principal.
Whether the payment stays predictable depends on the rate type. A fixed rate locks in the same monthly figure for the entire interest-only period. A variable rate tied to an index can shift up or down at each adjustment, which means you need reserves to absorb a spike. The note itself should specify the rate type, any index used, how often adjustments occur, and caps on how much the rate can move.
What Happens When the Interest-Only Period Ends
Once the interest-only window closes, the full original principal has to be repaid. Notes handle that transition one of two ways.
Recast to Amortization
The gradual option recalculates the payment so the entire principal is retired by the note’s maturity date. The catch is the shortened amortization window. A 30-year note with a 10-year interest-only period leaves only 20 years to pay off the same principal that would otherwise have been spread across 30. Monthly payments after the recast can jump to two or three times the interest-only amount, even if the rate has not changed.3Office of the Comptroller of the Currency. Interest-Only Mortgage Payments and Payment-Option ARMs
Balloon Payment at Maturity
The alternative is a balloon: the entire outstanding principal comes due in one lump sum on the maturity date. This is common in commercial financing and short-term bridge loans, where the borrower plans to sell the underlying asset or refinance before the balloon hits. If neither happens, the borrower defaults, and on a secured note the lender can foreclose on the collateral.
Many notes also reset the interest rate at the transition point to a market index. A borrower who budgeted around the old rate can face a double hit: a higher rate combined with principal repayment for the first time.
Risks Worth Weighing Before You Sign
Interest-only notes front-load the benefits and back-load the pain.
- Payment shock. When the interest-only period ends, payments can double or triple. Borrowers who stretched to afford the initial payment are the most exposed.3Office of the Comptroller of the Currency. Interest-Only Mortgage Payments and Payment-Option ARMs
- No equity buildup. Because no principal is paid during the interest-only phase, you build zero equity through payments. If the property’s value drops, you can owe more than the asset is worth.
- Refinance risk on balloon notes. A balloon assumes you can refinance or sell before maturity. If credit markets tighten, values decline, or your finances change, refinancing may not be available, and missing the balloon means losing the collateral.
- Rate adjustment exposure. On variable-rate notes, rising rates increase payments even during the interest-only phase, with no offsetting reduction in principal.
These risks are manageable when you have a clear exit strategy and reserves to absorb surprises. They turn dangerous when the interest-only structure was chosen only because a fully amortizing payment was unaffordable.
Key Legal Provisions in the Note
A promissory note is more than a payment schedule. The legal terms decide what happens when something goes wrong.
The note must clearly identify the lender and borrower, the principal, the interest rate, and the payment schedule. Beyond those basics, several provisions matter more than most borrowers realize.
A default clause defines exactly what counts as a breach. Missed payments are the obvious trigger, but default provisions routinely cover other events: letting property insurance lapse, filing for bankruptcy, or breaking financial covenants written into the agreement.
An acceleration clause lets the lender demand the entire remaining principal, plus accrued interest, immediately after a default. A long-term debt becomes due overnight. This is the enforcement mechanism that gives a promissory note real teeth.
If the note is secured, you pledge specific collateral, typically real property or equipment. A separate security agreement or deed of trust gives the lender the right to foreclose or repossess after a default. Unsecured notes offer no such remedy, which is why they usually carry higher interest rates.
A prepayment penalty clause specifies a fee the borrower owes for paying the principal off early. These clauses protect the lender’s expected interest income. If you plan to sell or refinance during the interest-only period, negotiate this term carefully; a steep penalty can wipe out the benefit of refinancing at a lower rate.
The note should also designate a governing law, meaning which state’s statutes control interpretation. States differ on allowable interest rates, foreclosure procedures, and available remedies, so the choice matters.
Usury Limits on the Interest Rate
Every state sets a maximum interest rate for private loans through usury laws. Caps vary widely, but most fall somewhere between 6% and 25% depending on the state, the type of borrower, and the loan amount. Charging above the legal limit can void the interest obligation entirely, and in some states the lender faces criminal penalties. Commercial loans, loans above certain dollar thresholds, and loans to business entities are often exempt from the tightest caps. Before setting a rate, both parties should check the ceiling in the state whose law governs the note.
Tax Treatment for the Lender
Interest received during the interest-only phase is ordinary income, reported for the year it comes in. If you pay $10 or more in interest to any single recipient, you must issue IRS Form 1099-INT documenting the total interest paid. The commonly cited $600 threshold applies to a narrower category of trade-or-business interest payments; for most promissory note arrangements, the $10 threshold is the trigger.4Internal Revenue Service. Instructions for Forms 1099-INT and 1099-OID
Tax Treatment for the Borrower
Whether you can deduct the interest depends entirely on what the borrowed money was used for.
Business and Investment Interest
Interest on debt used to finance a trade or business is generally deductible, but a cap applies. Under Section 163(j), the business interest deduction in any year cannot exceed the borrower’s business interest income plus 30% of adjusted taxable income. Any disallowed amount carries forward.5Office of the Law Revision Counsel. 26 U.S. Code 163 – Interest Interest on debt used to buy investment property is also deductible, but only up to your net investment income for the year.
Personal Debt and the Mortgage Interest Deduction
Interest on purely personal debt is not deductible. The major exception is qualified residence interest: if the note is secured by your primary or secondary home and the funds were used to buy, build, or substantially improve that home, the interest may be deductible on up to $750,000 of acquisition debt ($375,000 if married filing separately).6Internal Revenue Service. Publication 936 – Home Mortgage Interest Deduction Both conditions have to be met. A note secured by a home but used to fund a vacation does not qualify.
Keep clear records of how the proceeds were spent. The IRS can challenge a deduction if the use of funds does not match the claimed category.
Below-Market Interest and Imputed Interest Rules
Private notes between family members or business associates sometimes carry little or no interest. The IRS does not allow that. Under Section 7872, if a loan charges interest below the Applicable Federal Rate, the IRS treats the forgone interest as though it were actually paid. The lender owes income tax on interest never received, and depending on the relationship, the difference may also be treated as a taxable gift from lender to borrower.7Office of the Law Revision Counsel. 26 U.S. Code 7872 – Treatment of Loans With Below-Market Interest Rates
The IRS publishes Applicable Federal Rates monthly in three tiers: short-term (three years or less), mid-term (over three years but not more than nine), and long-term (more than nine years). A note must charge at least the AFR in effect when the loan is made to stay out of imputed-interest territory. Check the current month’s rates before setting the number.
Two exceptions soften the rule for smaller loans between individuals. If total outstanding loans between two people stay at or below $10,000, the imputed interest rules generally do not apply, unless the borrower used the money to buy income-producing assets. For loans up to $100,000, the imputed interest the lender must recognize is capped at the borrower’s net investment income for the year, and if that income is $1,000 or less, no imputed interest is recognized at all.7Office of the Law Revision Counsel. 26 U.S. Code 7872 – Treatment of Loans With Below-Market Interest Rates
Family loans are where people most often get tripped up. A parent lending a child $200,000 for a house at 1% interest will owe income tax on the difference between 1% and the AFR, even though the parent never collected that money. The fix is simple: charge at least the AFR, put the terms in writing, and document the payments.