The U.S. Internal Revenue Service for 2020 has lowered the rate used to calculate the deductible costs of operating an automobile for business purposes. The standard mileage rates for the use of a car, van, pickup or panel truck will be 57.5 cents per mile driven, half a cent lower than in 2019. The deductible mileage rate is based on an annual study of the fixed and variable costs of operating an automobile. Many companies use the standard rate to calculate reimbursements for employees who use personal vehicles for business.