The mileage deduction is about the miles you can deduct on an itemized tax returns at the end of the year. Each year, the IRS sets the rate each mile driven for work is worth. The 2017 standard mileage rate set by the IRS is 53.5 cents per mile for business drives. You can see how someone who drives a lot for work can earn a pretty hefty deduction. The mileage reimbursement allows you to add the miles they drive to an expense report. Companies reimburse these people for these miles.