The Internal Revenue Service (IRS) increased the optional standard mileage rates for the final six months of 2011. The rate will increase to 55.5 cents per mile for all business miles driven from July 1, 2011 through December 31, 2011. This is an increase of 4.5 cents from the 51 cent rate in effect for the first six months of 2011. The IRS made this special adjustment for the final months of 2011 in recognition of gasoline price increases. The IRS normally updates the mileage rates once per year in the fall for the next calendar year. Taxpayers may use the optional standard rates to calculate the deductible costs of operating an automobile for business and other purposes.