The maximum amount you can deduct on your income tax return is the fair market value of your car. Fair market value is the price a willing buyer would pay and a willing seller would accept for the car, when neither party is compelled to buy or sell, and both parties have reasonable knowledge of the relevant facts.
Some fundraisers have mistakenly claimed that donors can, in all cases, deduct the full value of their cars as found in a used car guide (such as "blue book" value). A used car guide may be a good starting point to value your car, but you should exercise caution. The IRS will only allow a deduction for the fair market value of the car, which may be substantially less than the "blue book" value.
Depending on the amount of the deduction you claim for the car, you may have to file an additional form with the IRS with your Form 1040. If the deduction you are claiming for a donated car is greater than $500, you must complete Section A of Form 8283. If the deduction you are claiming is greater than $5,000, you must get a written appraisal of your car (see Written Appraisal below). You must also complete Section B of Form 8283, which must include the signature of an authorized official of the charity, and attach it to your return.
Your written appraisal must be from a qualified appraiser. See Publication 561, Determining the Value of Donated Property. The appraisal must be made no more than 60 days before you contribute the car.