If you are reimbursed under an accountable plan, then reimbursements may be tax free. For example, if reimbursements for your mileage exceed the IRS standard mileage rate, then only amounts up to the rate are tax free; excess reimbursements are taxable.
A statutory method of depreciation allowing accelerated rates for most types of property used in business and income-producing activities during the years 1981 through 1986. It has been superseded by the modified accelerated cost recovery system (MACRS) for assets placed in service after 1986.