The IRS allows you to claim a tax deduction of the amount the car sold for. Your tax-deductible receipt will be for the car's full sale price.
You can claim the fair market value of the car, up to $500. According to the IRS, it is up to you to determine the fair market value of your car.
The most important consideration when choosing a charity is determining its "exempt" status. To be eligible for a tax deduction, the car must be donated to a tax-exempt nonprofit
organization, most commonly known as a 501(c)(3) organization.
To verify if an organization is tax-exempt, use the IRS search tool, or ask to see the organization’s IRS letter recognizing it as tax-exempt.
According to the IRS -
Kars4kids is a classified 501(c)(3) charity organization. You can check with your tax advisor or accountant to determine the amount of your benefit.The deduction is of value only if the donor itemizes his or her deductions. For a more detailed overview the IRS publishes a Donors Guide to Car Donation.