The net investment income tax (NIIT) is an additional 3.8% tax that kicks in if you have investment income and your MAGI exceeds $200,000 for single filers, $250,000 for those married filing ...

If you don’t know what Net Investment Income Tax (NIIT) is, you’re not alone. This relatively new tax began a little over a decade ago but the number of taxpayers subject to the tax has increased.

The 3.8% net investment income tax, which is added to the regular income tax, covers more than you might think.