Net Investment Income Tax (NIIT) Calculator
Find out whether you owe the 3.8% net investment income tax — and exactly how much — based on your income and investment earnings.
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Interest, dividends, capital gains, rental/royalty, passive income.
How the NIIT works
The Net Investment Income Tax is a 3.8% surtax on investment income for higher earners. It applies to the lesser of:
- your net investment income, or
- the amount your MAGI exceeds the threshold ($200,000 single / $250,000 joint / $125,000 MFS).
These thresholds are not indexed for inflation, so more taxpayers cross them over time. Capital gains, Roth conversions, and RMDs can all push MAGI up.
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General estimate of the federal 3.8% NIIT. Not tax advice. Verify with IRS Form 8960 or a tax professional.