Sales Tax Deduction for Cars: Old vs. New Deductions

Car buyers can deduct their sales tax expense when purchasing a new vehicle. This deduction, available for 2009 only, is different than the existing itemized deduction for sales taxes. The differences between the two deductions are subtle. Here's a question I recently received about this new sales tax deduction:

I have a question concerning the sales tax deduction for purchases for a new car. To my understanding prior to the new administration we could already deduct sales tax from major purchases, car included, ... itemize or use a general sales deduction calculator at IRS.gov ... what's the difference with that and the 'new sales tax deduction for purchases on a new car?' Seems as if this is a device to get people to purchase an item that'll depreciate by 40% ASAP for something that already exists for new or old cars. Am I misunderstanding something?

So to help straighten things out, here's the differences between the two deductions.

First, the new vehicle sales tax deduction will be an additional amount added to a person's standard deduction.

Second, for taxpayers who itemize, the new vehicle sales tax deduction will be taken in addition to a deduction for state and local income taxes.

Third, for taxpayers who opt for the sales tax deduction in lieu of the deduction for state and local income taxes, any sales tax paid will be added to the deduction amount found using the IRS's sales tax calculator.

Fourth, the new deduction is available only for the purchase of a new vehicle, including cars, trucks, RVs, motor homes, and motorcycles. The old deduction for sales tax is available for boats and aircraft as well as for leased cars and trucks.