The 3.8% Medicare Surtax is outlined in IRC Sec. 1411 under Chapter 2A. In addition to Code Sec. 1411, this past December the IRS also released proposed regulations to aid and guide taxpayers effected by this new tax.
In fairness, the IRS claims that these measures are all about compliance to ensure that tax return preparers are following the new regulations in order to protect the taxpaying public (insert dramatic music here).