Write-offs for extended car warranties

Q. When I bought a car for business this year, I also purchased the warranty. Can I deduct the full amount of the warranty this year? O.W., Nashville, Tenn.

A. No. You must write off the cost over the life of the extended warranty. How to do it: Divide the cost by the number of months of the full warranty period. Then multiply the number of months the warranty is in effect for the year by the monthly amount.

Tip: If you use the car less than 100 percent for business, you can only deduct the portion of the expense attributable to business use.