What it is:
Yield maintenance is a kind of prepayment fee that borrowers pay to banks to reimburse them for the loss of interest resulting from the prepayment of a loan.
How it works (Example):
The formula for the yield maintenance premium is:
Let's assume John takes out a $1,000,000 mortgage from ABC Bank at 7%. The borrower begins making monthly payments on the mortgage. Two years later, interest rates decline dramatically, and John chooses to refinance the loan. To do so, John repays the $1,000,000 loan by taking out a similar loan at a lower interest rate from a different lender and paying off the first loan. As a result, ABC Bank loses eight years of interest payments that it would have otherwise gotten had interest rates not declined enough to induce the borrower to go elsewhere.
The bank calculates yield maintenance based on current interest rates and projected rates over the course of the life of the mortgage.