QSBS purchased after September 28, 2010, is eligible for a $10M or 10x the initial investment tax exclusion on 100% of capital gains taxes, alternative minimum taxes (AMT), and net investment income tax (NIIT). Even though NIIT was not established until January of 2013, QSBS purchased before September 28, 2010, is subject to the 3.8% of NIIT for the portion of the non-excludable gain.
This article does not constitute legal or tax advice. Please consult with your legal or tax advisor with respect to your particular circumstance.