In finance, negative amortization, also known as NegAm, is an amortization method in which the borrower pays back less than the full amount of interest owed to the lender each month. The shorted amount is then added to the total amount owed to the lender. Such a practice would have to be agreed upon before shorting the payment so as to avoid default on payment. Also known as deferred interest or Graduated Payment Mortgage (GPM).

Negative amortization only occurs in loans in which the periodic payment does not cover the amount of interest due for that loan period. The result of this is that the loan balance (or principal) increases by the amount of the unpaid interest. The purpose of such a feature is to increase affordability, or add payment savings and payment flexibility to a loan.

Neg-Ams also have what is called a recast period and recast principal balance cap based on Federal and State legislation. The recast period is usually 60 months (5 years). The recast principal balance cap (also known as the "neg am limit") is usually up to a 125% increase of the amortized loan balance over the original loan amount. States and lenders can offer products with lesser recast periods and principal balance caps; but cannot issue loans that exceed their state and federal legislated requirements under penalty of law.

Starting rates on negative amortization or minimum payment option loans can be as low as 1%. This is the payment rate, not the actual interest rate. The payment rate is used to calculate the minimum payment. Other minimum payment options include 1.95% or more.