Your deduction for a donated car, boat, or airplane is generally limited to the gross proceeds from its sale by the qualified organization. This rule applies if the claimed value of the donated vehicle is more than $500. In certain cases, you can deduct the vehicle's fair market value (FMV).
For details, see IRS Publication 526 Charitable Contributions
Strict substantiation requirements apply to prevent donors from claiming inflated deductions for donated vehicles where the charity actually received much less on a sale to raise cash.
You must attach to your return Copy B of the Form 1098-C Contributions of Motor Vehicles, Boats, and Airplanes
(or other statement containing the same information as Form 1098-C) you received from the organization. The Form 1098-C (or other statement) will show the gross proceeds from the sale of the vehicle. If you e-file your return, you must attach Copy B of Form 1098-C to Form 8453 and mail the forms to the IRS.
If you do not attach Form 1098-C (or other statement), you cannot deduct your contribution. You must get Form 1098-C (or other statement) within 30 days of the sale of the vehicle. But if either of the exceptions described on page 8 of IRS Publication 526 applies, you must get Form 1098-C (or other statement) within 30 days of your donation.