Hybrid arrangements come in various forms but share a common goal: Each is designed to enhance beneficial tax results by exploiting differences in tax treatment under the laws of two or more countries.  Anti-hybrid rules were adopted as part of the T.C.J.A., which was enacted in the waning days of 2017.  In December 2018, the I.R.S. released proposed regulations that provide guidance on anti-hybrid rules adopted by Congress.  New terms must be understood, including (i) the deduction/no inclusion (“D./N.I.”) rules, (ii) tiered hybrid dividends, (iii) the hybrid deduction account (“H.D.A.”) that addresses timing, and (iv) a principal purposes test denying the benefit of the dividends received deduction.  If final regulations are adopted by June 22, 2019, they will be effective retroactively to the date of enactment of the statute.  In their article, Beate Erwin and Fanny Karaman explain the workings the proposed regulations.