Rates are set by fiscal year, effective October 1 each year. Find current rates in the continental United States ("CONUS Rates").
The MACRS class for an addition or improvement is generally determined by the MACRS class of the property to which the addition or improvement is made.
For example, if you put an addition on a rental home that your depreciating over 27.5 years, the addition is depreciated as 27.5-year residential rental property. The period for figuring depreciation begins on the date that the addition or improvement is placed in service, or, if later, the date that the property to which the addition or improvement was made is placed in service.
An addition or improvement you make to depreciable property is treated as separate depreciable property. The recovery period begins on the later of the following dates:
If the improvement you make is qualified leasehold improvement property or qualified restaurant property, the GDS recovery period is 15 years (39 years under ADS).
After October 22, 2004:
Qualified improvements placed in service after October 22, 2004 must be depreciated using the straight-line method over a 15-year recovery period. Qualified improvement are improvements to an interior portion of a nonresidential building, provided:
After May 12, 1993:
Depreciate an addition or improvement to nonresidential real property placed in service after May 12, 1993 over 39 years using straight-line depreciation (MACRS real estate rates).
Start depreciation in the month the addition or improvement is placed in service.