This document contains final regulations relating to the depreciation of property subject to section 168 of the Internal Revenue Code (MACRS property) and the depreciation of computer software subject to section 167. Specifically, these final regulations provide guidance regarding the additional first year depreciation allowance provided by sections 168(k) and 1400L(b) for certain MACRS property and computer software. The regulations reflect changes to the law made by the Job Creation and Worker Assistance Act of 2002, the Jobs and Growth Tax Relief Reconciliation Act of 2003, the Working Families Tax Relief Act of 2004, the American Jobs Creation Act of 2004, and the Gulf Opportunity Zone Act of 2005.