The recent acquisition of Covidien by Medtronic has brought what may be some unwanted attention to companies attempting to move operations overseas for tax-inversion purposes.  The Obama administration is trying to crack down on these strategies, and Treasury Secretary Jack Lew has now issued a letter to congressional tax-writing committees urging lawmakers to limit inversions through a legislative overhaul.  Lew would like immediate governmental action   that is simultaneously retroactive to May 2014, a decision which could have an impact on similar deals that have already taken place.