As a practical matter, it's unlikely to be a problem. The value of your tax deduction is limited to (a) the price the charity sold the car for, or (b) the price you originally paid, whichever is lower. If audited, you would only need reasonable proof that you paid more for the car than it was sold for. That might be the blue book value from back then if you bought it used, or the sticker price if you bought it new. Web sites like cars.com and other sites can probably help you come up with a reasonable estimate of what you paid.