The Internal Revenue Service has increased the optional standard mileage rates for the final six months of 2011. Taxpayers may use the optional standard rates to calculate the deductible costs of operating an automobile for business and other purposes. The rate will increase to 55.5 cents a mile for all business miles driven from July 1st through December 31st of this year. This is an increase of 4.5 cents from the 51-cent rate in effect for the first six months of 2011. The new six-month rate for computing deductible medical of moving expenses will also increase by 4.5 cents -- to 23.5 cents a mile, up from 19 cents for the first six months of 2011. The rate for providing services for charitable organizations remains at 14 cents a mile.