Step 1 – What is the unit of property to which you should apply the improvement rules?
For the Year Placed in Service - This rule, only for non-building property, is triggered at the time you initially placed the unit of property into service. If at the time the unit of property is first placed in service, you properly treat the component of the unit of property as being within a different MACRS class than the MACRS class for the unit of property of which the component is a part, or you properly depreciate the component using a different depreciation method than the depreciation method used for the unit of property of which the component is a part, then you must treat the component as a separate unit of property.
谢谢！
或bonus depreciation第一年减80%。
建的过程中应该有很多费用满足Safe harbors，是不是都可以直接减去呢？我买过尚未建的房子，建商的Invoice中有很多低于2500的。
烤箱是equipment， 无论如何第一年都可以减掉。
https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations
Step 1 – What is the unit of property to which you should apply the improvement rules?For the Year Placed in Service - This rule, only for non-building property, is triggered at the time you initially placed the unit of property into service. If at the time the unit of property is first placed in service, you properly treat the component of the unit of property as being within a different MACRS class than the MACRS class for the unit of property of which the component is a part, or you properly depreciate the component using a different depreciation method than the depreciation method used for the unit of property of which the component is a part, then you must treat the component as a separate unit of property.
假如你建新房，你想把新房里面的空调机器算de minimus safe harbor，那么你必须把这个空调单独折旧，而不是算到新房里面按照27.5 年折旧。
这个就和你说得cost segregation有关了。民居房例子不太好，但是比如说旅馆每个房间都有一个小冰箱和微波炉。如果你买来的旅馆，可以把几十个上百个冰箱和微波炉单独折旧，这个叫做cost segregation。我还是从你那里听来的。
那么，你盖新旅馆，买来几十个上百个冰箱和微波炉安到房间里面，能不能按照de minimus safe harbor处理呢？为什么不可以？似乎是可以的啊？ （de minimus 有没有总值的限制？好像没有啊）
你举的旅馆中的冰箱和微波炉的例子，过于特殊，因为它们是明显的Personal Property， 用179 Expense或bonus depreciation就可以减掉大部或全部，名正言顺，毫无争议。但我不知用de minimus safe harbor是否合适。
如果我们排除电器等完整的Personal Property，比如in-service前，修一房子，刷墙2100，地板2300，窗户1花500，窗户2花500... 窗户N花500；门1花300，门2花300...门M花300， 等等等等，满足safe harbor的总额是20万，那请问，这20万可以在第一年完全减掉吗？我认为不可以，我也怀疑IRS会允许。
所以，我感觉Safe play 还是，把in-service之前的所有费用加到basis，然后尽可能多地分出Personal Property，愿意折腾的话就做个cost segregation，这样名正言顺，没有争议。
just my 2 cents.