In December 2017, Congress passed the Tax Cuts and Job Act (TCJA), one of the most impactful pieces of tax reform legislation since 1986. The Act creates changes affecting U.S. taxpayers, both domestically and internationally, including lower tax rates, altered allowable deductions, mandatory deemed/constructive repatriation of offshore income, expansion of Subpart F income rules, and critical changes to ownership attribution rules relating to certain foreign entities. Review these changes and identifies future areas of dispute as the IRS tries to enforce the new law.