Private Mortgage Insurance, also known as PMI, is a supplemental insurance policy you may be required to obtain in order to get a mortgage loan. PMI is usually required when your loan-to-value ratio - the amount of your mortgage loan divided by the value of your home - is greater than 80 percent. If your down payment on a home is less than 20 percent of the appraised value or sale price, you must obtain private mortgage insurance, known as PMI, with your lender. This will enable you to obtain a mortgage with a lower down payment because your lender is now protected against any default on the loan. PMI charges vary depending on the size of the down payment and the loan, but they typically amount to about one-half of 1 percent of the loan. Most home buyers need PMI because 20 percent of the sale price on a home is a lot of money; for instance, that's $20,000 on a $100,000 home. Home buyers must maintain the PMI premiums until they cross that one-fifth-of-principal threshold, a process that can take years in longer-term mortgages.Mortgage insurance premiums are not tax deductible.

Example:
Let's say you put down 10 percent or $10,000 on a $100,000 house. The lender multiplies the 90 percent loan, or $90,000, by .005. The result is an annual PMI of $450, which is divided into monthly payments of $37.50.

Tip:
Keep track of your payments on the principal of the mortgage. When you reach the point where the loan-to-value ratio hits 80 percent, notify the lender that it is time to discontinue the PMI premiums. The Homeowners Protection Act of 1998, which took effect in 1999, requires lenders to tell the buyer at closing how many years and months it will take for them to reach that 80 percent level and cancel PMI. Lenders must automatically cancel PMI when the balance hits 78 percent.

Note:
The law does allow lenders to continue requiring PMI all the way down to 50 percent equity for so-called high-risk borrowers. Traditionally, those loans that are considered riskier include reduced documentation loans, in which customers provide less proof of income and other information during the approval process. Loans for people with spotty credit histories and higher debt-to-income ratios also fall into this category. Additionally, some FHA loans require payment of PMI throughout the entire life of the loan.

Avoid PMI:
In today's market, there are new ways to avoid mortgage insurance even when you don't have the standard 20 percent down payment. Some lenders will waive the mortgage insurance requirement if the buyer accepts a higher interest rate on the mortgage loan. The rate increases generally range from .75 percent to 1 percent, depending on the down payment. The advantage is that mortgage interest is tax deductible. (Use the mortgage calculator to see what your payment would be.)