Each year the IRS adjusts certain tax numbers for inflation and tax law changes. Here are some of the adjusted numbers you’ll need for your 2012 tax planning. Standard mileage rate for business driving remains at 55.5¢ a mile. Rate for medical and moving mileage decreases to 23¢ a mile. Rate for charitable driving remains at 14¢ a mile. Section 179 maximum first-year expensing deduction decreases to $139,000, with a phase-out threshold of $560,000. Transportation fringe