If you own a small business or are self-employed you may be able to claim the standard mileage rate deduction on your income tax return. The standard mileage rate is a set amount of money that is credited to each mile driven that the Internal Revenue Service allows small businesses and self-employed individuals to claim as an expense on their return. The standard mileage rate is sometimes referred to as the mileage per diem. All mileage that is accumulated strictly for business purposes may be used to calculate the standard mileage rate deduction. It should be noted that mileage that is accumulated when driving from your home to the office does not qualify for the standard mileage rate deduction.