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NIIT Calculator - Net Investment Income Tax

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Enter your MAGI, filing status, and net investment income to calculate your 3.8% Net Investment Income Tax (NIIT).

NIIT Calculator

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NIIT owed
$1,140.00
MAGI over threshold
$30,000
Taxable base (lesser of the two)
$30,000
Based on IRC Section 1411, filed on Form 8960. Thresholds are statutory and NOT inflation-adjusted (unchanged since 2013). Not tax advice - consult a tax professional for your specific situation.

The formula

NIIT = 3.8% x MIN(Net Investment Income, MAGI - Threshold) Threshold: $200,000 (Single/HoH), $250,000 (MFJ), $125,000 (MFS) Only applies once MAGI exceeds the threshold - and only on the SMALLER of your investment income or the excess MAGI
Example

MFJ filer, MAGI $280,000, net investment income $60,000: $30,000 over the $250,000 threshold. Since $30,000 is smaller than the $60,000 of investment income, tax applies only to the $30,000 - NIIT = 3.8% x $30,000 = $1,140.

Step-by-step guide

  1. Calculate your Net Investment Income - interest, dividends, capital gains, passive rental income, and royalties, minus directly related deductible expenses.
  2. Enter your MAGI and filing status to find your threshold and how much you exceed it by.
  3. Read your NIIT - the "lesser of" rule means high investment income doesn't automatically mean high tax if your MAGI is only modestly over the threshold.

Why these thresholds catch more people every year

The $200,000/$250,000/$125,000 thresholds were set in the original 2013 legislation and have never been adjusted for inflation - a rarity in the tax code, where most thresholds rise annually. As wages and asset values have grown over more than a decade, a threshold that once applied mainly to the top 10% of earners now reaches further down the income distribution each year, purely from ordinary income growth rather than any change in the law. This "fiscal drag" effect means more taxpayers become subject to NIIT over time even if their real, inflation-adjusted financial position hasn't meaningfully changed.

Common mistakes

Applying 3.8% to your full net investment income instead of the lesser of NII or excess MAGI - if your MAGI is only modestly over the threshold, the tax is capped at that smaller excess amount, not your full investment income.
Including wages, self-employment income, or retirement distributions as "net investment income" - NIIT applies specifically to investment-type income; ordinary earned income and most retirement account distributions aren't counted.

Frequently asked questions

Does NIIT apply at the state level too?

No - NIIT is a federal-only tax with no state-level equivalent in most states, unlike income tax which typically has both federal and state components.

What income counts toward net investment income?

Interest, dividends, capital gains (including from stocks, real estate, and crypto), passive rental income, royalties, and annuity income. It excludes wages, active self-employment income, Social Security, most retirement distributions, and tax-exempt bond interest.

Is anything withheld toward NIIT during the year?

No - unlike wage withholding, nothing is automatically withheld for NIIT, so taxpayers who expect to owe it typically need to plan for it through quarterly estimated tax payments.

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