Last Updated: April 2026
The Net Investment Income Tax (NIIT) was introduced by the Affordable Care Act in 2013. It is a 3.8% surtax on top of regular income tax, applying to investment income for taxpayers above income thresholds. On a $500,000 capital gain, NIIT adds $19,000 in tax on top of the federal capital gains rate. Understanding what triggers NIIT — and what planning strategies reduce it — is critical for high-income investors, real estate owners, and business sellers.
Net Investment Income (NII) includes income from passive sources and investment assets. The IRS groups NII into three categories:
All taxable interest income (savings accounts, bonds, CDs), qualified and non-qualified dividends, and annuity income is included in NII. Tax-exempt municipal bond interest is specifically excluded — this is one reason high-MAGI investors favor municipal bonds.
Rental income and income from passive business activities (businesses where you do not materially participate) are included in NII. If you own a rental property and do not qualify as a Real Estate Professional (750+ hours/year), all rental net income is passive and therefore subject to NIIT. If you own a passive interest in a partnership or S-corporation, the income flowing through to you is subject to NIIT.
Capital gains from selling investment property are included: stock gains, bond gains, real estate gains (unless excluded by §121 exclusion on primary residence), capital gain distributions from mutual funds, crypto gains, and gains from selling passive business interests. The §121 exclusion ($250K/$500K gain excluded on primary residence sale) specifically reduces NIIT — the excluded gain does not count in NII. However, any gain above the §121 limit IS subject to NIIT.
The following do NOT count as NII and are not subject to the 3.8% surtax:
Several strategies reduce exposure to the 3.8% NIIT:
NIIT applies to the lesser of NII or (MAGI minus threshold). Strategies to reduce MAGI: maximize pre-tax 401(k) contributions (reduces MAGI by up to $23,000 in 2024, or $30,500 if 50+), contribute to an HSA (reduces MAGI), take available above-the-line deductions (student loan interest, alimony in legacy situations, self-employed health insurance). If MAGI is only slightly above the threshold, reducing it below can eliminate the NIIT entirely.
Active business income does not trigger NIIT. If you are a passive partner in a business, increasing your material participation to meet the 500-hour test converts income from passive (NIIT subject) to active (not NIIT subject). For real estate investors, qualifying as a Real Estate Professional (IRS §469) removes rental income from passive status, eliminating NIIT on rental income (though this requires 750+ hours/year in real estate activities and it exceeding 50% of your work time).
Tax-exempt bond interest is excluded from both regular income tax and NIIT. For investors in the 37% bracket with NIIT exposure, the after-tax yield comparison of munis vs taxable bonds: a 5% taxable bond yield nets 5% × (1 - 37% - 3.8%) = 2.96% after-tax; a 3.2% muni bond yield nets 3.2% (tax-free). Munis win at these rates for NIIT-exposed investors.
Roth IRA distributions are not included in MAGI or NII — they are completely invisible for NIIT purposes. Converting traditional IRA to Roth creates income in the conversion year (increasing MAGI and potentially triggering NIIT), but permanently removes future growth from NIIT exposure. SEP-IRA contributions (up to $69,000 in 2024 for self-employed) reduce MAGI substantially.
Instead of recognizing a large capital gain in one year (pushing MAGI far above the threshold and triggering NIIT on the full gain), spreading a business or real estate sale over multiple years via installment reporting keeps each year's MAGI closer to the threshold. NIIT on $100K/year over 5 years may be less than NIIT on a $500K lump gain in year 1.
Gains invested in a QOZ fund are deferred; gains on QOF appreciation held 10 years are excluded from income entirely — excluding them from NII and NIIT. The December 31, 2026 QOZ deadline creates urgency for investors with large deferred gains who want NIIT exposure managed.
Rental income is passive income subject to NIIT by default. However, if you qualify as a Real Estate Professional and make a grouping election for your rental activities, the rental income is treated as non-passive — removing it from NII. Requirements: 750+ hours in real property trades or businesses; more than 50% of your total working time. Spouses can combine hours on a jointly owned rental for the 750-hour test. This is one of the most valuable NIIT elections for landlords with significant rental income.
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NIIT Help for US Expats →No — Traditional IRA and 401(k) distributions are not included in net investment income (NII) for NIIT purposes. However, they do increase your Modified Adjusted Gross Income (MAGI), which is the other side of the NIIT equation. If IRA distributions push your MAGI above the $200K/$250K threshold, they can cause your OTHER investment income (capital gains, dividends) to become subject to NIIT. So IRA distributions don't pay NIIT themselves but can make other income subject to NIIT. Roth IRA distributions are completely excluded — they don't increase MAGI or NII.
Yes — the §121 exclusion for primary residence capital gains (up to $250,000 for single filers, $500,000 for married) specifically reduces both regular capital gains and NIIT. The gain excluded under §121 does not count as Net Investment Income on Form 8960. However, any gain above the §121 exclusion amount IS included in NII and subject to NIIT. Example: married couple sells primary residence for $800,000 gain. $500,000 is excluded under §121 (no regular tax, no NIIT). $300,000 is taxable as capital gain and, if MAGI exceeds $250,000, subject to the 3.8% NIIT ($11,400 additional tax).
Yes — cryptocurrency gains (including Bitcoin, Ethereum, and other digital assets) are treated as capital gains from property sales, which are included in Net Investment Income. If your MAGI exceeds the $200K/$250K threshold and you have crypto gains, the 3.8% NIIT applies to those gains in addition to the regular capital gains rate. Short-term crypto gains (held less than 1 year) are taxed as ordinary income for regular tax purposes but are still classified as NII (investment income) for NIIT purposes.