The OECD Partnership Report is a significant contribution to the discussion of how to treat partnerships for tax treaty purposes when two states categorize a partnership-like entity differently, either as transparent or as opaque. This article examines why different treatment of other states' bodies (to use a neutral term) for tax purposes can arise, particularly from the way in which states classify foreign bodies, thus giving rise to part of the problem addressed in the OECD Partnership Report. The focus is more on the categorization of partnerships than on the differences in tax treatment, which is the main focus of the OECD Report.