How to Calculate Yield Maintenance

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In the real estate industry, lenders make money through fees and interest. Anything that threatens a lender’s expected cash inflows can cause a drop in the return on investment, which means less money in the lender’s pocket. Yield maintenance is a legal provision that real estate lenders routinely incorporate into their contracts. Its purpose is to reimburse the lender for lost interest income when a borrower pays off a mortgage early due to falling interest rates.

The Lender's Cost of Prepayment

Lenders expect a specified return, or yield, on the money they lend. In the mortgage market, homeowners have the option to refinance their mortgages when interest rates fall. That’s good for the homeowners but creates a problem for lenders.

The lender’s problem is that the interest rate at which the lump sum payment they receive when a prepayment occurs will be lower than that of the original mortgage, due to falling interest rates. When they receive the lump sum, lenders know that, at the very least, they can reinvest it in two-year Treasury notes to earn the current, lower interest rate on top-quality debt. This reduces the yield on the original loaned amount because part of it will now be earning a lower interest rate.

Naturally, the mortgage lender will look to redeploy the prepaid money in subsequent mortgage loans. However, the standard convention is for the yield maintenance penalty to use the Treasury note interest rate as the basis of measuring the potential lost yield.

Thus, the yield maintenance penalty plugs the gap between the new yield and original one. It is an additional sum of money added to the payoff amount that the homeowner pays when refinancing a mortgage.

How to Calculate Yield Maintenance

The size of the yield maintenance fee is the difference in the present values of the earnings on the mortgage with and without the prepayment.

The calculation is:

Yield Maintenance Fee = (C -R) x F x B

Where:

• C​ is the loan interest rate,
• R​ is the current Treasury note yield,
• F​ is the present value factor and
• B​ is the unpaid loan balance as of the prepayment date.

F, the present value factor, recognizes that money is worth more when it’s in hand today rather than at a future date – that’s why lenders charge interest in the first place. The present value of a cash flow stream is how much it would be worth if today you collected it all at once.

The value of F is equal to (1 - ((1 + R)^-N/12)))/R, where N is the number of months. This formula discounts the stream of future interest cash inflows by the current Treasury note rate to provide the present value of those inflows.

Using a Yield Maintenance Calculator

You could calculate the yield maintenance penalty by plugging all the numbers into the equation. Fortunately, a spreadsheet or online yield maintenance calculator makes the job much easier.

To take an example, imagine a homeowner decides to refinance her 30-year, 4.5 percent mortgage after 10 years because interest rates have fallen. The original mortgage loan amount was \$300,000, of which \$243,778 remains. Assume that the current two-year Treasury note yield is 2.2447 percent.