2025 Threshold For Net Investment Income Tax. The magi thresholds the tax applies to are as follows (for 2025): For single filers, this threshold is $200,000, while for married couples filing jointly, it is $250,000.
The net investment income tax (niit) is 3.8%. It is applied to either your net investment income or the amount by which your magi exceeds the threshold for your status, whichever is less.