Negative Amortization occurs when your monthly payments do not cover all the interest owed. The interest that is not paid in the monthly payment is added to your principal loan balance. This means that even after making many payments, you could owe more than you did at the beginning of the loan. Negative amortization can occur when an ARM has a payment cap that results in monthly payments that are not high enough to cover the interest due or when the minimum payments are set at an amount lower than the amount you owe in interest.