On September 22, 2014 the U.S. Department of Treasury announced new rules targeting companies that try to avoid U.S. income taxes by moving their headquarters overseas (a so-called “inversion”). The Treasury Department is still fleshing out the details of the guidance but has effectively placed companies on notice that deals that close on or after September 22, 2014 will be subject to new rules issued by the Treasury Department. To better understand the Treasury Department’s new rules, some background on “inversions” is helpful.