In a year when your stock gains, dividends, or rental income grow, you may notice an extra line on your return: a 3.8% Net Investment Income Tax (NIIT) on top of regular income tax. Introduced in 2013, the NIIT applies to investment income of taxpayers above certain income levels, and because the thresholds are not indexed for inflation, more people are caught every year. This article explains how the tax is computed, which income is and is not covered, the 2026 thresholds, the rule that nonresident aliens are exempt, how it works for international couples filing jointly, and the important point for U.S. citizens living in Japan that foreign tax credits cannot offset it, including the Federal Circuit’s August 2026 decisions.
The Computation: 3.8% of the Lesser of Two Amounts
The NIIT equals 3.8% of the lesser of (Form 8960):
- your net investment income for the year, or
- the amount by which your modified adjusted gross income (MAGI) exceeds the threshold.
| Filing status | Threshold (not indexed) |
|---|---|
| Single, head of household | $200,000 |
| Married filing jointly, qualifying surviving spouse | $250,000 |
| Married filing separately | $125,000 |
| Estates and trusts | Undistributed net investment income above the top bracket threshold ($16,000 for 2026) |
For example, a married couple with MAGI of $300,000 and net investment income of $80,000 has an excess over the threshold of $50,000, so the tax is $50,000 x 3.8% = $1,900. MAGI adds back wages excluded under the foreign earned income exclusion, so taxpayers abroad who use the exclusion are closer to the threshold than their AGI suggests.
What Is and Is Not Net Investment Income
| Included | Excluded |
|---|---|
| Interest and dividends (including qualified dividends) | Wages, self-employment income, and income from businesses in which you materially participate |
| Gains on stocks, bonds, cryptocurrency, and real estate (home sale gain only above the $250,000 / $500,000 exclusion) | Distributions from 401(k)s, IRAs, and other qualified plans (although they raise MAGI) |
| Rental and royalty income, net of expenses and depreciation | Social Security benefits and tax-exempt municipal bond interest |
| Income from passive activities (partnership or S corporation interests without material participation) | Rental income of real estate professionals from a trade or business, subject to conditions |
| Earnings in nonqualified annuities and trading income | Tax-free life insurance proceeds, Alaska Permanent Fund dividends |
Expenses properly allocable to investment income reduce net investment income, including rental expenses and depreciation, investment interest, and the portion of state income tax attributable to investment income. Investment advisory fees and other miscellaneous itemized deductions, however, are permanently suspended for regular tax and therefore cannot reduce net investment income either.
Nonresident Aliens Are Not Subject to the NIIT
The NIIT applies to U.S. citizens and residents (green card holders and those meeting the substantial presence test). Nonresident aliens are exempt. A Japanese investor living in Japan who receives U.S. dividends owes no NIIT on Form 1040-NR; the 10% treaty withholding settles the U.S. tax. In a dual-status year, only investment income earned during the resident period is subject to the tax.
International couples filing jointly
When a U.S. citizen or resident files jointly with a nonresident spouse under a Section 6013(g) election, a separate NIIT election is available. Without it, the nonresident spouse’s investment income is excluded from the NIIT, but the U.S. spouse must compute the tax using the married filing separately threshold of $125,000. If the couple elects into the NIIT jointly, the nonresident spouse’s investment income is included and the $250,000 joint threshold applies. Which is better depends on how much investment income the nonresident spouse has.
U.S. Citizens in Japan: No Offset from Foreign Tax Credits
A U.S. citizen or green card holder living in Japan pays 20.315% Japanese tax on dividends and gains in Japanese brokerage accounts and must also report them in the U.S. Regular income tax is relieved by the foreign tax credit on Form 1116, but the NIIT sits in Chapter 2A of the Internal Revenue Code, not Chapter 1, and the statutory foreign tax credit does not apply to it. Taxpayers had won partial victories in the Court of Federal Claims arguing that tax treaties independently allow a credit, but on August 31, 2026, the Federal Circuit reversed those decisions in Bruyea and Christensen, holding that treaty-based foreign tax credits cannot offset the NIIT either. The practical result is that U.S. citizens resident in Japan bear both Japan’s 20.315% and the U.S. 3.8% on investment income above the threshold.
Practical Ways to Manage the NIIT
- Manage MAGI: contributions to 401(k)s, IRAs, HSAs, and self-employed retirement plans reduce MAGI. Roth conversions and large gains push it up, so spreading them over several years helps.
- Harvest losses: realized losses reduce net investment income. The $3,000 annual limit applies only to offsetting ordinary income; gains and losses offset each other without limit.
- Municipal bonds: tax-exempt interest is excluded from both net investment income and MAGI.
- Real estate: claim all rental expenses and depreciation, and check whether you can qualify as a real estate professional so that rental income is treated as non-passive.
- Home sales: only gain above the Section 121 exclusion is subject, so document improvements that add to basis.
- Estimated tax: wage withholding does not cover the NIIT, so include it in estimated payments to avoid underpayment penalties.
Frequently Asked Questions
Is an IRA withdrawal subject to the NIIT?
Distributions from qualified retirement plans are not net investment income. They do count toward MAGI, however, so in a year with dividends or gains they can push you over the threshold and expose that other investment income to the tax.
Are cryptocurrency gains covered?
Yes. Cryptocurrency is treated as property, and gains on sale are capital gains included in net investment income. Staking rewards and similar income are generally treated as investment income unless earned in a trade or business.
If I move back to Japan, will my U.S. dividends still be subject to the NIIT?
Not once you are a nonresident alien; investment income after that point is outside the tax. If you remain a U.S. citizen or keep your green card, however, you are still treated as a resident, the NIIT continues to apply even while you live in Japan, and Japanese tax cannot be credited against it.
This article is provided for general informational purposes only and does not constitute individual tax advice. Please review current IRS rules and case law, and consult a qualified U.S. tax professional before acting.
Summary
The NIIT adds 3.8% on investment income for taxpayers above fixed thresholds of $200,000 (single) and $250,000 (joint), covering interest, dividends, gains, and rental income while excluding wages and retirement plan distributions. Nonresident aliens are exempt, so Japanese investors living in Japan are unaffected, but U.S. citizens and green card holders in Japan are covered, and the Federal Circuit’s August 2026 decisions confirm that foreign tax credits cannot offset the tax. Managing MAGI, harvesting losses, deducting allocable expenses, and adjusting estimated payments are the basics, and any year with a large sale or Roth conversion deserves a projection in advance.
Related Articles
- Navigating US Stock Dividend Taxation and the Limits of Foreign Tax Credit: A Deep Dive into US-Japan Tax Treaty and Double Taxation Relief
- US Stock and Cryptocurrency Tax Filing: A Comprehensive Guide to Capital Gains and Loss Carryforwards
- Mastering Capital Gains Tax on US Home Sales: The $250,000 Exclusion Rule Explained
- Investing in U.S. REITs as a Nonresident: Dividend Withholding, the 10% Treaty Rate, and the FIRPTA Exemptions
TAX PREPARER SWITCH CAMPAIGN
Switch your tax preparer and get 50% off your U.S. tax return this year.
Show us last year's invoice and we take 50% off the fee (up to $500, first year only). Prepared and signed by an IRS Enrolled Agent, in English or Japanese.
See the switch campaign →