Congress has extended tax deductions for homeowners paying private mortgage insurance through 2010.

But to qualify for the deduction you must have bought or refinanced your home since Jan. 1, 2007.

Families with adjusted gross incomes of up to $100,000 can deduct 100% of their insurance premiums, much the same as they deduct property taxes. The deduction is then phased out up to an adjusted gross income of $110,000.

Mortgage insurance guarantees lenders will be repaid if the borrowers default. It's almost always required if you hold less than 20% of the equity in your home.

Your equity is the difference between your home's market value and what you owe on your mortgage (and home equity loan, if you have one).

The annual premiums run about 0.5% to 0.75% of the outstanding balance, $500 to $750 a year for every $100,000 you owe.

Our worksheet on 9 steps to cancel PMI can help you decide whether you have enough equity to drop that insurance.

Whether you're buying a home or refinancing an existing mortgage, we have a mortgage calculator that can help you make the right decisions.