On June 23, 2011, the Internal Revenue Service (IRS) announced an increase in the optional standard mileage rates for the final six months of 2011. Ordinarily, the IRS updates the rates once a year in the fall for the following calendar year. This year, due to fuel prices, the IRS has made a mid-year change. The change will become effective as of July 1, 2011 and will increase the rate for business miles from 51 cents per mile to 55.5 cents per mile. Though the IRS rate is optional and businesses are free to determine their own rate for mileage reimbursement, the IRS rate is often used by employers as a benchmark for reimbursement to their employees for mileage on work-related trips.