The IRS mileage tax deduction is a deductible credit that can be written off of taxes, a medical or moving expense or an expense related to charitable service. The 2014 rates for these write-offs per mile were 56 cents for business, 23.5 cents for medical or moving and 14 cents for charitable service.
The business rates are based on both fixed and variable costs of running an automobile each year, while the medical and moving rates are based only on variable costs. Mileage rates for 2015 are slightly different. If a taxpayer uses a vehicle for business only, he can write off the entire expense of the vehicle, but if he uses it for other purposes, he can only write off what he uses for business purposes.
Tax payers have the option to use the calculated costs of operating their vehicle instead, but may not use the standard mileage rate if they have used a Section 179, or any depreciation method under the Modified Accelerated Cost Recovery System, or MACRS, for the vehicle they are claiming mileage on. Additionally, the standard mileage rate can only be used for four vehicles at one time. There are other conditions with which one can not use the standard mileage rate.