The 3.8% Medicare surcharge, more widely known as the Net Investment Income Tax or NIIT, has been a point of confusion and controversy since its enactment in 2013. Originally designed to help fund “Obamacare” health coverage, it primarily targets high-income earners. Because the NIIT thresholds aren’t adjusted for inflation, however, more taxpayers are finding themselves subject to the tax over time.
Here’s a breakdown of what you need to know about this tax, especially if you work abroad, pay taxes to a foreign jurisdiction, have a foreign spouse, own foreign companies, or deal with complex investments.
What Is the Net Investment Income Tax?
In broad terms, the NIIT is a 3.8% surtax on “net investment income” for high-income individuals.
Net investment income must be distinguished from “earned” income, which is generated through labor, services, or active business involvement. Investment income includes interest, dividends, capital gains (this includes net capital gain from the sale of a principal residence that exceeds the exemption of $250,000 for single filers and $500,000 for joint filers), annuities, royalties and passive rents as well as income from businesses, such as trading of financial instruments and commodities and businesses that are considered “passive” with respect to the taxpayer.
Notably, some income sources are exempt from the NIIT, including distributions from qualified retirement plans (such as 401(k)s, 403(b)s, IRAs) and tax-exempt municipal bonds. This makes sense—Congress doesn’t want to discourage retirement savings or investments in public infrastructure projects.
Who Is Affected By The NIIT?
Not everyone falls under the NIIT’s purview, but its reach has grown over time due to stagnant income thresholds that are not adjusted for inflation. To be subject to this tax, two conditions must be met:
1. The taxpayer must have net investment income.
2. The taxpayer’s modified adjusted gross income (MAGI) must exceed certain thresholds.
Here’s a quick glance at the MAGI thresholds:
Filing Status/ Threshold Amount
- Married filing jointly/ $250,000
- Married filing separately/ $125,000
- Single / $200,000
- Head of household (with qualifying person)/ $200,000
- Qualifying widow(er) with dependent child/ $250,000
If both conditions apply, the taxpayer will owe NIIT on the lesser of net investment income or the excess of MAGI over the thresholds.
MAGI is generally adjusted gross income (Form 1040 for 2023, Line 11) with certain adjustments coming into play for the American abroad who has taken foreign earned income or housing exlusions, or has income from certain foreign corporations.
Special NIIT Rules For Americans Abroad
The NIIT requires Americans living overseas to add back foreign earned income and housing exclusions when calculating their MAGI. Taxpayers with Controlled Foreign Corporations or Passive Foreign Investment Companies may face additional adjustments. Foreign tax credits cannot offset NIIT, meaning the American abroad who must pay NIIT will really feel the pinch if paying taxes to a foreign country.
NIIT And Foreign Corporation Shareholders
For certain shareholders in CFCs and PFICs, NIIT calculations become quite intricate. The tax covers dividends and gains from disposing of CFC or PFIC stock. Anti-deferral rules mean U.S. investors in these entities must often pay tax on certain corporation earnings that have not yet been distributed to them.
Under the NIIT rules, the U.S. shareholder is allowed to make an election to include the undistributed income from the CFC or PFIC in his net investment income for the 3.8% NIIT in the year in which the U.S. shareholder pays U.S. income tax on that CFC or PFIC undistributed income. This election enables the shareholder to treat the undistributed income from the CFC or PFIC consistently as taxable income for both regular U.S. income tax and for NIIT. Without this election, taxpayers face a messy situation: NIIT hits when they finally receive the distribution, but regular federal income tax won’t apply since the income was already taxed earlier.
NIIT And Nonresident Aliens, Dual Status-Taxpayers
Nonresident aliens are completely exempt from the NIIT. This is a significant consideration for NRAs earning passive income from U.S.-based investments. No NIIT!
Special rules apply to dual-status taxpayers and those electing to be treated as U.S. residents for tax filing purposes. Looking closer at these issues, below.
A dual-status taxpayer is a foreign individual who has been temporarily in America and who is a tax resident for part of the year, but a non-resident alien for the balance of the year. Such a dual-status taxpayer is subject to the NIIT only with respect to the portion of the year during which the individual is a U.S. resident. This means that only income earned during the portion of the year for which the taxpayer is a U.S. resident can potentially be subject to the NIIT. The statutory thresholds, however, are not reduced or prorated for the dual-status taxpayer.
A common situation involves elections made under Internal Revenue Code 6013(g) and (h). Generally, these elections allow a U.S. citizen or resident to treat their nonresident alien (NRA) spouse as a U.S. resident for tax purposes, enabling them to file a joint return and be taxed on worldwide income. Making one of these elections, however, does not automatically extend the treatment to the NIIT.
To subject the NRA spouse’s net investment income to the NIIT, a specific election must be made on IRS Form 8960, which governs the application of the NIIT. Without this special election on Form 8960, the default rule exempts the NRA spouse from the NIIT, meaning their investment income remains outside the scope of this 3.8% surtax and leaves the U.S. citizen or resident spouse subject to the NIIT threshold amount applicable to married taxpayers filing separately. This default treatment underscores the importance of making an explicit election if joint NIIT treatment is desired, as it directly impacts tax liability and filing requirements.
Conclusion
NIIT issues will add complexity to the tax return preparation process since deeper analysis will be required to determine optimal positions, for example, considering whether to make certain elections. The overseas American will often have very special Net Investment Income Tax considerations. As the NIIT continues to evolve and potentially expand, taxpayers—particularly those with complex foreign or investment portfolios—should stay informed. Understanding its rules, exemptions, and nuances can save money and avoid unwanted surprises.
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