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IRS Form 8960: Net Investment Income Tax (NIIT)
How to calculate the 3.8% Net Investment Income Tax on Form 8960. Covers what counts as net investment income, the MAGI thresholds, and strategies to reduce.
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How to calculate the 3.8% Net Investment Income Tax on Form 8960. Covers what counts as net investment income, the MAGI thresholds, and strategies to reduce.
This guide is designed for first-pass understanding. Start with core terms, then apply the framework in your own account workflow.
Form 8960 calculates the Net Investment Income Tax (NIIT); a 3.8% surtax on investment income for individuals with modified adjusted gross income above $200,000 (single) or $250,000 (married filing jointly). Combined with the top long-term capital gains rate of 20%, the effective top rate on investment income can reach 23.8%. Like its companion tax on Form 8959, the NIIT thresholds are not indexed for inflation, drawing more taxpayers into its reach each year.
The Net Investment Income Tax was enacted alongside the Additional Medicare Tax as part of the Affordable Care Act (ACA) in 2010, taking effect on January 1, 2013. While the Additional Medicare Tax (Form 8959) targets high earners' wages and self-employment income, the NIIT was designed to capture investment income; interest, dividends, capital gains, rents, royalties, and passive business income; that had previously been exempt from any Medicare-related taxation.
Before the ACA, there was a notable asymmetry in the tax code: wages were subject to both income tax and payroll taxes (Social Security and Medicare), while investment income was subject only to income tax. The NIIT partially closed this gap by imposing a tax on investment income that mirrors the Medicare tax on wages.
The 3.8% rate was not arbitrary; it was designed to approximate the combined employer and employee Medicare tax rate (1.45% + 1.45% + 0.9% = 3.8%). The goal was to ensure that high-income individuals paid a similar level of Medicare-related tax whether their income came from wages or investments.
As with the Additional Medicare Tax, the NIIT thresholds ($200,000 for single filers, $250,000 for MFJ) were not indexed for inflation. In the decade-plus since the tax took effect, inflation has eroded the real value of these thresholds significantly, expanding the number of taxpayers subject to the NIIT well beyond what was originally intended.
You must file Form 8960 if you have net investment income and your modified adjusted gross income (MAGI) exceeds:
The 3.8% tax is applied to the lesser of your net investment income or the amount by which your MAGI exceeds the applicable threshold. This means:
Net investment income includes interest, dividends, capital gains, rental and royalty income, non-qualified annuities, and income from passive business activities. It does not include wages, self-employment income, Social Security benefits, or distributions from most retirement plans.
The 3.8% tax applies to the lesser of your net investment income or the amount by which your modified adjusted gross income exceeds the threshold ($200,000 single, $250,000 married filing jointly). So if your MAGI is $280,000 and your net investment income is $50,000, you pay 3.8% on $30,000 (the excess over the threshold).
Gain excluded under the Section 121 home sale exclusion ($250,000 single, $500,000 married) is not subject to the NIIT. However, any gain above the exclusion amount is net investment income and may be subject to the 3.8% tax if your MAGI exceeds the threshold.
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IRS Schedule D: Capital Gains and Losses Explained
Types of income included in net investment income:
Types of income excluded from net investment income:
This section calculates your total net investment income. You list each category of investment income (interest, dividends, annuities, rental/royalty income, capital gains, and other investment income) and then subtract investment expenses that are properly allocable to the investment income.
Deductible investment expenses include investment interest expense, investment advisory fees (to the extent they are still deductible; TCJA suspended the miscellaneous itemized deduction), state and local income taxes allocable to investment income, and penalties on early withdrawal of savings.
For most taxpayers, MAGI for NIIT purposes is the same as their regular adjusted gross income (AGI). The modification primarily affects taxpayers with foreign earned income excluded under Section 911; the exclusion is added back to AGI for purposes of this calculation.
This is where the tax is actually calculated. The 3.8% rate is applied to the lesser of net investment income (from Part I) or the excess of MAGI over the applicable threshold (from Part II). The result is entered on your Form 1040 as an additional tax.
The NIIT thresholds have remained unchanged since 2013. Various legislative proposals have sought to modify the tax; some by expanding it to cover active business income for high earners, others by indexing the thresholds to inflation. The Biden administration proposed expanding the NIIT to cover all income above $400,000 for certain taxpayers, which would have significantly broadened the tax. This proposal was not enacted.
The real estate professional exemption continues to be an area of significant IRS scrutiny. Taxpayers who claim to materially participate in rental activities to avoid the NIIT on rental income must meet strict hourly and substantive tests. The IRS has increased audits of this claim, particularly for taxpayers with high rental income who also have other full-time occupations.
For taxpayers subject to both the NIIT and the Additional Medicare Tax, the combined additional burden is significant — up to 0.9% on earned income plus 3.8% on investment income, on top of regular income tax. This has made tax planning around the $200,000/$250,000 thresholds a priority for financial advisors.
Clarity tracks all your investment income — dividends, interest, capital gains, and rental income — in real time alongside your earned income. By aggregating your complete financial picture, Clarity shows you exactly where you stand relative to the NIIT threshold throughout the year. This visibility helps you make informed decisions about when to realize capital gains, whether to harvest losses to offset gains, and how to structure investment income to minimize the 3.8% surtax.
For more details, visit the official IRS page for Form 8960.
This article is educational and does not constitute tax advice. Consult a qualified tax professional for guidance specific to your situation.
Learn how to report capital gains and losses on Schedule D, including short-term vs. long-term rates, the $3,000 loss deduction, and wash sale rules.