Cross border tax planners are expected to know all there is about various provisions of Subchapter N of the Internal Revenue Code. An example might be the G.I.L.T.I. provisions adopted in the Tax Cuts & Jobs Act of 2017. They are not expected to know more mundane provisions of tax law such as rules that apply to married persons filing a joint tax return. In their article, Andreas Apostolides and Stanley C. Ruchelman examine a recent hiccup in G.I.L.T.I. provisions that focus computations in a top-down way. What happens when the marital property regime adopted by the married couple is that of separate property (or they are domiciled in a common law jurisdictions), one spouse separately owns C.F.C.’s with losses, the other spouse separately owns C.F.C.’s with positive earnings, and none of the C.F.C.’s generates Subpart F income? Is the married couple treated as one unit or simply an aggregate of two separate taxpayers? The answer may be troubling.