It is best to have a study completed for the year the building or improvements are placed in service. However, US Tax Code allow taxpayers to “catch up” on the depreciation that was not claimed from the first day the property was placed in service without amending prior years’ tax returns. Furthermore, the US Tax Code allows for the “catch up” period all in the first year rather than over four years, when the Revenue Procedure 99-49 was first introduced. A cost segregation study can be performed on any property constructed, acquired or remodeled since Jan. 1, 1986.