Learn how the 3.8% Net Investment Income Tax works, which income it covers, its MAGI thresholds, Form 8960 reporting, and California treatment.
The Net Investment Income Tax, or NIIT, is a 3.8% federal tax on certain investment income of individuals, estates, and trusts whose income exceeds an applicable threshold. For an individual, the tax equals 3.8% of the lesser of net investment income or modified adjusted gross income above the filing-status threshold.
NIIT is separate from regular income tax and capital-gain tax. A long-term capital gain can receive a preferential federal rate and still be included in the NIIT calculation. California does not impose the federal NIIT, although the same investment income may be taxable under California income-tax rules.
For individuals, use this framework:
3.8% × lesser of (net investment income or MAGI above the threshold) = NIIT
The statutory thresholds are:
These individual thresholds are not indexed for inflation. Crossing a threshold does not subject all investment income to NIIT; the lesser-of formula limits the taxable base.
Example: Jordan is single with $210,000 of MAGI. Jordan has $25,000 of gross investment income and $1,000 of deductions properly allocable to that income, producing $24,000 of net investment income. MAGI exceeds the $200,000 threshold by $10,000. The taxable base is the lesser amount, $10,000, and the NIIT is $380.
Net investment income generally includes taxable interest, dividends, capital gains, annuities, royalties, and rents. It can also include income from a trade or business that is passive to the taxpayer and income from a trade or business of trading financial instruments or commodities.
Gain from selling stocks, mutual funds, digital assets, a second home, or rental property can enter the calculation. The calculation generally uses taxable gain after basis, exclusions, and recognized loss rules — not gross sale proceeds. Properly allocable deductions can reduce net investment income, but regular deduction limitations still apply.
Net investment income generally does not include wages, unemployment compensation, Social Security benefits, tax-exempt interest, most self-employment income from an active business, or distributions from qualified retirement plans and IRAs. However, an excluded item can still increase MAGI or affect another component of the return, and retirement distributions can push MAGI over the threshold even though the distribution itself is not net investment income.
Rental income is commonly included, but exceptions and participation rules matter. Income from a nonpassive trade or business generally falls outside NIIT unless the business trades financial instruments or commodities. A rental real-estate professional who materially participates may have nonpassive rental income, but that classification requires a detailed Section 469 analysis.
S-corporation and partnership owners must distinguish active operating income, passive pass-through income, wages, guaranteed payments, and gain from selling an ownership interest. Merely owning a business does not produce one universal NIIT result.
Form 8960 calculates net investment income, MAGI, the threshold excess, and tax. An individual reports the result with Form 1040; an estate or trust reports its NIIT through Form 1041. The estate-and-trust threshold is linked to the amount at which the highest income-tax bracket begins and therefore changes with inflation, unlike the fixed individual thresholds.
Form 1099-B, Form 1099-DIV, Form 1099-INT, Form 1099-DA, Schedule K-1, Schedule D, Schedule E, and Form 4797 can all feed the calculation. Form 8960 is not simply a duplicate of Schedule D because it combines several income classes and applies its own deduction and business-activity rules.
For most U.S. taxpayers, NIIT MAGI begins with adjusted gross income. Taxpayers claiming the foreign earned income exclusion generally add back specified excluded foreign earned income and adjust related deductions. "Modified adjusted gross income" has no single universal formula: NIIT MAGI is not necessarily the same as MAGI for an IRA, education credit, or premium tax credit.
The 3.8% NIIT is a federal tax and is not separately imposed on the California return. California generally taxes interest, dividends, digital-asset gains, rents, and capital gains at regular state income-tax rates, with no lower California rate for long-term capital gain.
Federal and California basis, depreciation, passive-loss carryovers, or source rules can differ. Those differences can change the investment income reported to California even though California does not copy Form 8960. California residents generally report worldwide income; nonresidents and part-year residents must analyze California sourcing.
Heath Income Tax can help calculate Form 8960, reconcile passive and investment income, and project the combined federal and California effect of a major transaction.
Is NIIT the same as the Additional Medicare Tax?
No. Both use a 3.8% or 0.9% Medicare-related framework, but NIIT applies to specified investment income, while Additional Medicare Tax applies to wages, Railroad Retirement Tax Act compensation, and self-employment income over separate thresholds.
Does NIIT apply to cryptocurrency gains?
It can. A recognized digital-asset gain held for investment is generally included in net investment income when the taxpayer also meets the MAGI test.
Can a capital loss reduce NIIT?
Capital-loss rules and Form 8960 adjustments can reduce included gain, but only recognized and allowable losses count. Capital-loss limitations and carryovers still apply.
The definitions and examples on this page are for informational purposes only and do not constitute tax advice. Tax laws change frequently and individual circumstances vary. Consult a qualified tax professional before making decisions based on this content.
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