The Internal Revenue Service typically updates its mileage rate in December before the start of a new tax year, although it occasionally makes midyear adjustments. The business mileage rate reflects the cost of operating a vehicle, including gas, insurance and repairs, explains the IRS.
Between 1997 and 2015, the IRS made two midyear mileage rate adjustments to reflect rapidly increasing gas costs. In July 2008, the IRS raised the rate from 50.5 cents a mile to 58.5 cents, notes the agency. The change followed a major spike in the cost of gas, which went from $3.10 a gallon in January 2008 to $4.11 a gallon in July, reports the Department of Energy.