If you use a dwelling unit as a residence and rent it for fewer than 15 days during the year, you don’t report any of the rental income; it’s tax free. But you can’t deduct any expenses as rental expenses.
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 It has been superseded by the modified accelerated cost recovery system (MACRS) for assets placed in service after 1986.