2024 Threshold For Net Investment Income Tax Return. The net investment income tax (niit) is a surtax on high amounts of investment income. The net investment income tax thresholds aren't adjusted for inflation, and as a result many taxpayers pay niit.

Net investment income tax thresholds are based on tax filing status and income (as defined by modified adjusted gross income). To calculate the niit, let’s first look at the statutory threshold amounts.