Glossary term
Net Investment Income Tax (NIIT)
The net investment income tax is a 3.8% tax that can apply to certain net investment income above statutory income thresholds.
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What Is the Net Investment Income Tax?
The net investment income tax, or NIIT, is a 3.8% federal tax that can apply to certain net investment income when a taxpayer's income is above statutory thresholds. It can apply to individuals, estates, and trusts.
The tax is separate from regular income tax and capital gains tax. It is reported on IRS Form 8960 when it applies.
Key Takeaways
- NIIT is a 3.8% federal tax on certain net investment income.
- It applies only when income is above the applicable threshold.
- Investment income can include interest, dividends, capital gains, rents, royalties, and certain passive income.
- The rules are technical, especially for trusts, estates, business income, and passive activities.
How NIIT Is Applied
For individuals, NIIT generally applies to the lesser of net investment income or the amount by which modified adjusted gross income exceeds the threshold for the taxpayer's filing status. That structure means the tax depends on both investment income and overall income.
Income Type | Possible NIIT Treatment |
|---|---|
Interest and dividends | Often included in net investment income. |
Capital gains | Often included when from investment assets. |
Rental income | May be included depending on activity and exceptions. |
Wages | Generally not net investment income. |
Tax-exempt interest | Generally excluded from net investment income. |
Planning Context
NIIT can affect the after-tax return on taxable portfolios, real estate, passive business interests, and trust income. It can also matter in years with large capital gains, business sales, concentrated stock sales, or Roth conversion planning that raises modified adjusted gross income.
Because the thresholds are not the same as ordinary tax brackets and the rules interact with other parts of the tax return, NIIT should be modeled alongside capital gains, deductions, credits, Medicare tax, and state tax.
What to Watch
NIIT is not a tax on every investment account. Retirement account distributions are generally not net investment income, though they can raise modified adjusted gross income and indirectly affect whether the threshold is crossed.
The practical question is not simply whether someone has investments. It is whether the taxpayer has net investment income and income above the applicable threshold.
The Bottom Line
The net investment income tax is an additional federal tax on certain investment income for higher-income taxpayers. Its impact depends on income level, investment income type, and how the tax return fits together.