Net Investment Income Tax (NIIT)
A 3.8% surtax on the lesser of net investment income or modified AGI exceeding $200,000 (single) or $250,000 (married filing jointly). Applies to interest, dividends, capital gains, and rental income.
The Net Investment Income Tax (NIIT) is a 3.8% surtax introduced by the Affordable Care Act in 2013, applying to individuals, estates, and trusts with investment income above certain thresholds. For individuals, the 3.8% applies to the lesser of your net investment income or the amount by which your modified AGI exceeds $200,000 (single filers), $250,000 (married filing jointly), or $125,000 (married filing separately). These thresholds are not adjusted for inflation.
Net investment income subject to NIIT includes interest, dividends, capital gains, rental and royalty income, non-qualified annuity income, and income from passive business activities. It does not include wages, self-employment income, Social Security benefits, distributions from retirement accounts (IRAs, 401(k)s), or income from active business participation.
The NIIT is calculated on Form 8960 and added to your regular tax liability. Strategies to reduce NIIT include maximizing contributions to tax-deferred retirement accounts (which lower MAGI), investing in tax-exempt municipal bonds, converting passive business activities to active participation, and timing capital gain realizations across tax years to stay below the threshold. Combined with the 20% long-term capital gains rate, the top federal rate on investment income can reach 23.8%.
How it works
The Net Investment Income Tax is a flat 3.8% surtax that applies to the smaller of two numbers: your net investment income for the year, or the amount by which your modified AGI exceeds a threshold that depends on filing status — $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately. Because it taxes the lesser of the two figures, someone with a huge MAGI overage but modest investment income only pays NIIT on the smaller investment-income number, and vice versa.
You calculate and report it on Form 8960, and it's added on top of your regular tax liability. Net investment income counted here includes interest, dividends, capital gains, rental and royalty income, non-qualified annuity income, and income from passive business activities — but not wages, self-employment earnings, Social Security benefits, or distributions from retirement accounts like IRAs and 401(k)s.
Because these MAGI thresholds are not indexed for inflation, more taxpayers drift above them every year even without any real increase in purchasing power. Common ways to manage NIIT exposure include maximizing pre-tax retirement contributions to lower MAGI, holding tax-exempt municipal bonds, converting a passive business activity to active participation, and timing when you realize capital gains. Stacked on top of the 20% top long-term capital gains rate, NIIT can push the effective federal rate on investment income as high as 23.8%.
Example: NIIT on investment income above the threshold
A single filer has modified AGI of $230,000 for the year — $30,000 above the $200,000 threshold — and $50,000 of net investment income from dividends and capital gains.
NIIT applies to the lesser of the $50,000 net investment income or the $30,000 MAGI overage, so the 3.8% rate applies to $30,000. That produces a Net Investment Income Tax bill of $1,140, on top of the regular income tax owed on that same income.
Frequently asked questions
What income counts toward the Net Investment Income Tax?
What are the NIIT income thresholds?
Can I reduce how much NIIT I owe?
Related Terms
Net Investment Income Tax (NIIT)
A 3.8% surtax on investment income (interest, dividends, capital gains, rental income) for individuals with modified AGI above $200,000 (single) or $250,000 (married filing jointly).
Capital Gains
The profit from selling a capital asset (stocks, real estate, etc.) for more than its purchase price. Capital gains are classified as short-term or long-term based on holding period.
Passive Activity Loss
A loss from a business or rental activity in which you do not materially participate. Passive losses can generally only be deducted against passive income, not wages or portfolio income.
Adjusted Gross Income (AGI)
Your gross income minus specific adjustments such as student loan interest, IRA contributions, and self-employment tax. AGI is the starting point for calculating your taxable income.