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what is the definition of these two items

  1. Prior Depreciation Equivalent
  2. AMT Prior Depreciation Equivalent 

I believe I understand what #1 is, it's the sum of the Previous Year's accumulated depreciation. In my case, the fraction (i.e .26 or .25, etc.) of the standard mileage amount through all previous years where the vehicle was used.

 

What is

 

AMT Prior Depreciation Equivalent ?  no idea what AMT refers to and why the amount might be different that 

#1 above?