When you drive your own car to volunteer for a nonprofit organization, those miles may be deductible on your taxes. The IRS allows a deduction for miles driven while providing services to a qualified charitable organization, but the rate is much lower than the business mileage rate. The charitable mileage rate is set by law at 14 cents per mile, which has not changed in many years. You can also deduct parking fees and tolls related to your volunteer driving. Keep a log of your volunteer trips including the date, destination, and miles driven so you have documentation if needed.