Negative amortization is a loan condition in which a scheduled payment is less than the interest accruing that period, so the unpaid interest is added to the principal balance and the amount owed grows rather than shrinks. It arises when a loan's pay rate sits below its accrual rate, deferring interest into future debt.
How Negative Amortization Works
Negative amortization works through the gap between two rates: the accrual rate that determines interest owed and the pay rate that sets the required payment. When the pay rate is lower, the payment does not cover accrued interest. The shortfall, called deferred interest, is added to principal, and next period's interest is charged on the larger balance.
The Consumer Financial Protection Bureau describes the mechanic directly: "Interest that you failed to pay in a certain month is referred to as deferred interest. The result of adding that deferred interest to your principal balance is negative amortization." Because interest then compounds on a rising base, the balance climbs faster each period unless the borrower increases payments.
Worked example: a loan of $1,000,000 accrues at 6.0 percent annually, or 0.5 percent monthly, so month one interest is $5,000. If the required minimum payment is $3,000, the borrower defers $2,000. Principal rises to $1,002,000, and month two interest is charged on that figure, not the original.
Why Negative Amortization Matters
Negative amortization matters because it inverts the usual direction of debt. An operator underwriting a deal with a below-accrual pay rate is not building equity, but eroding it: the loan-to-value ratio worsens each month even if the asset holds value. The CFPB warns a borrower "can end up owing more on your mortgage than your home is worth."
The exposure concentrates at recast. Most negatively amortizing loans carry a balance cap, typically in the range of 110 to 125 percent of the original principal. When the balance hits that ceiling, the lender recalculates the payment to fully amortize the higher balance over the remaining term. That payment jump, known as payment shock, can strain debt service coverage on a property that was underwritten to the minimum payment.
Example
A $1,000,000 payment-option loan accrues at 6.0 percent annually. The borrower pays a fixed $3,000 minimum against interest that grows as principal grows. The table tracks the first three months of deferral.
Month | Starting balance | Interest accrued (0.5%) | Payment | Deferred interest | Ending balance |
|---|---|---|---|---|---|
1 | $1,000,000.00 | $5,000.00 | $3,000 | $2,000.00 | $1,002,000.00 |
2 | $1,002,000.00 | $5,010.00 | $3,000 | $2,010.00 | $1,004,010.00 |
3 | $1,004,010.00 | $5,020.05 | $3,000 | $2,020.05 | $1,006,030.05 |
Each month the deferred interest grows because it is charged on a larger balance. At this pace the balance reaches the common 110 percent cap of $1,100,000 and triggers a recast to a fully amortizing, and materially higher, payment.
Variations and Edge Cases
Negative amortization appears in several structures. The distinction that matters is whether the deferral is optional, contractual, or an accident of a rate reset.
Structure | How negative amortization arises |
|---|---|
Payment-option ARM | Borrower selects a minimum payment below the interest-only amount |
Graduated-payment mortgage | Early payments are set below accrual by design, then step up |
Deferred-interest bridge loan | Accrued interest capitalizes to principal until a maturity or sale event |
ARM at a rate reset | A rate rises above the capped payment, deferring the difference |
Under federal Regulation Z, a loan that permits negative amortization cannot be a qualified mortgage, which removes it from that safe harbor and raises lender liability. Payment caps also limit how far a balance can grow before a mandatory recast.
Negative Amortization vs Amortization
Negative amortization is often confused with amortization. Amortization is the scheduled reduction of a loan balance through payments that cover all accrued interest plus a portion of principal, so the balance falls to zero by maturity. Negative amortization is the reverse: the payment covers less than accrued interest, so the balance rises.
Feature | Amortization | Negative amortization |
|---|---|---|
Payment vs interest | Payment exceeds interest | Payment below interest |
Principal direction | Falls each period | Rises each period |
Equity effect | Builds equity | Erodes equity |
End-of-term balance | Zero, if fully amortizing | Higher than original, until recast |
Frequently Asked Questions
What causes negative amortization?
Negative amortization is caused by a payment that is smaller than the interest accruing on the loan. The unpaid interest, called deferred interest, is added to principal, so the balance grows. It occurs when the pay rate is set below the accrual rate.
Is negative amortization ever allowed?
Negative amortization is allowed in certain loan structures, such as payment-option ARMs and graduated-payment mortgages, subject to disclosure. Under Regulation Z, a loan permitting negative amortization cannot qualify as a qualified mortgage, which increases lender liability.
What is a negative amortization cap?
A negative amortization cap is the maximum balance a loan can reach before a mandatory recast. It is typically set in the range of 110 to 125 percent of the original principal. When the balance hits the cap, the lender recalculates the payment to fully amortize the higher balance.