Net Investment Income Tax Guide
The Net Investment Income Tax (NIIT) is a 3.8% surtax on the lesser of your net investment income or the amount your modified adjusted gross income exceeds $200,000 ($250,000 married filing jointly).
Introduced as part of the Affordable Care Act in 2013, the NIIT applies an additional 3.8% on top of regular income tax and capital gains tax for high-income earners. This means long-term capital gains for affected taxpayers can be taxed at up to 23.8% (20% + 3.8%), and the top federal rate on investment income can reach 40.8% (37% + 3.8%).
Consider a married couple with $300,000 in wages and $50,000 in investment income (dividends and capital gains). Their MAGI is $350,000, which exceeds the $250,000 threshold by $100,000. The NIIT applies to the lesser of: $50,000 (net investment income) or $100,000 (excess MAGI). They owe 3.8% × $50,000 = $1,900 in additional tax. If their investment income had been $120,000, NIIT would apply to $100,000 (the excess), costing $3,800.
Net investment income includes interest, dividends, capital gains, rental income, royalties, non-qualified annuity income, and passive business income. It excludes wages, unemployment compensation, Social Security benefits, tax-exempt interest, and active business income. Actively managing a business (material participation) can exclude its income from NIIT.
Strategies to Reduce NIIT
Consider municipal bonds (tax-exempt interest is excluded from NIIT), defer capital gains to years when income is below the threshold, use installment sales to spread gains across multiple years, or increase retirement plan contributions to reduce MAGI. Charitable remainder trusts can also reduce both MAGI and net investment income simultaneously.
FAQs
Does NIIT apply to Roth IRA conversions?
Yes. The amount of a traditional-to-Roth IRA conversion is included in AGI and can push you above the NIIT threshold. While the conversion amount itself is not investment income, the higher MAGI makes more of your actual investment income subject to the 3.8% surtax. Plan large conversions for years when investment income is low.
How does NIIT interact with state taxes?
Most states do not have a separate NIIT-equivalent tax, though some conform to federal definitions. California, New York, and other high-tax states will tax NIIT-affected income at their ordinary rates, potentially pushing the total tax rate on investment income to 50% or more in the highest brackets.
Can NIIT be avoided by not selling investments?
Yes. Unrealized capital gains are not counted in net investment income. Simply holding appreciated assets avoids NIIT on those gains. However, at death, your heirs receive a step-up in basis, eliminating the income tax entirely (though estate tax may apply for large estates). This makes "buy and hold" particularly attractive for high-net-worth investors.