How much tax write off for a car donation?

the tax law changed in 2005, For most car donations, the deduction you receive is now directly related to the selling price of the vehicle. The IRS allows for a minimum deduction of $500 but for any deduction over $500 the charity must provide to the donor a written acknowledgment of the vehicle's selling price. (IRS form 1098c) you can get more information on tax deductions at the IRS site www.irs.gov or at donationwizard.com/taxes.jsp

If you donated the car to a registered charity, you can write off the value of the car.

The kicker is that it is up to YOU to determine the value of the car. You should get a receipt from the charity who you donated it to, and also keep some kind of documentation to substantiate its valuation (Blue Book record, appraisal, etc.).