What Is Negative Amortization?
Most people assume a loan balance only moves in one direction: down. Negative amortization is the exception, a structure where the amount owed can actually grow larger over time even while payments are being made.
The short answer
Negative amortization happens when a loan payment is smaller than the interest accruing on the balance, so the unpaid interest gets added to the principal instead of being paid off. The result is a loan balance that increases over time rather than decreases, even though payments are being made on schedule.
How negative amortization happens
- The payment doesn’t cover full interest. On a standard loan, each payment covers the interest due plus a portion of principal. With negative amortization, the payment covers less than the interest that accrued.
- The shortfall gets added to the balance. Whatever interest isn’t covered by the payment is tacked onto the principal, which means future interest is then calculated on a larger number — a mechanism related to how compound interest builds on itself, just working against the borrower here instead of for them.
- The balance can exceed the original loan amount. Over enough time, this can result in owing more than was originally borrowed, even with regular payments.
Which loans are more likely to include it
Negative amortization shows up most often in certain adjustable-rate loans that offer a minimum payment option lower than the interest-only payment, and in some structures involving ARM adjustment periods, index, and margin, where a payment cap limits how much a monthly payment can rise even when the rate itself has increased more. It can also appear temporarily in some forbearance arrangements, where accrued interest during a payment pause gets added to the balance rather than paid down immediately.
What it does to the loan over time
Because the balance grows instead of shrinking, a borrower in negative amortization is moving further from paying off the loan, not closer, for as long as the condition continues. This also affects home equity — since the loan balance is rising rather than falling, any equity gained from the property’s value has to outpace the growing loan balance just to keep the same amount of equity in place. Most loan structures that allow negative amortization include limits, such as a cap on how much the balance can grow before payments are required to increase.
How it differs from a standard amortizing loan
A standard amortizing loan is built so each payment covers all the interest due plus a bit of principal, meaning the balance steadily shrinks toward zero by a set payoff date — the same basic logic behind recasting a mortgage, which recalculates a smaller, still fully-amortizing payment after a lump sum is applied. Negative amortization breaks that pattern by allowing payments below the interest owed, at least for some period, which is why loans with this feature typically come with extensive disclosures explaining exactly how and when it can occur.
The takeaway
Negative amortization is a structural feature of certain loans where the payment doesn’t fully cover the interest owed, causing the balance to grow instead of shrink. Recognizing whether a loan includes this feature — and understanding the specific caps and conditions that govern it — is essential before assuming that steady payments automatically mean steady progress toward payoff.