What Is the Net Investment Income Tax (NIIT) and Who Owes It?

The Short Answer

The Net Investment Income Tax (NIIT) is a 3.8% surtax on certain investment income — think interest, dividends, capital gains, and rental income — for individuals, estates, and trusts whose income exceeds set thresholds. For most people it kicks in once modified adjusted gross income (MAGI) tops $200,000 (single) or $250,000 (married filing jointly), according to IRS.gov. It’s a separate line item calculated on Form 8960, layered on top of your regular income tax.

Where This Tax Came From

The NIIT isn’t part of the regular income tax brackets — it was enacted as part of the 2010 health reform package — specifically the Health Care and Education Reconciliation Act of 2010, passed alongside the ACA — and has applied to tax years beginning on or after Jan. 1, 2013, per the IRS’s Questions and Answers on the Net Investment Income Tax. Despite its statutory name — the “unearned income Medicare contribution” — the revenue is not deposited in the Medicare trust funds; it flows to the Treasury General Fund. The rationale was that investment income isn’t otherwise subject to payroll taxes the way wages are. A worker earning $150,000 in salary already pays Medicare tax withheld from every paycheck. Someone whose $150,000 comes from stock dividends and rental checks was, before 2013, paying no comparable tax on that income. The NIIT narrows that gap for high-income households.

Who Actually Owes It

Two conditions have to both be true:

1. Your modified adjusted gross income (MAGI) exceeds the threshold for your filing status.
2. You have net investment income for the year.

If either one is zero or negative, you owe no NIIT. This is why a high earner with no investment income (say, a surgeon who only has W-2 wages) pays $0 in NIIT, even though the Additional Medicare Tax might still apply to their wages separately.

The thresholds have not moved since the tax began in 2013 — they are fixed dollar amounts in the statute, not adjusted for inflation. That matters more each year as wages rise; more middle-to-upper-income households cross the line simply from cost-of-living raises and modest investment gains.

Estates and trusts have their own, much lower threshold — it’s tied to the top income tax bracket for trusts and does get adjusted annually for inflation. For 2026 that threshold is $16,000 (up from $15,650 for 2025) — the point at which the top 37% estate and trust bracket begins. Because it is adjusted annually, confirm the figure in the current Instructions for Form 8960 on IRS.gov before filing.

What Counts as “Net Investment Income”

The tax applies to the lesser of two numbers:

• Your net investment income, or
• The amount by which your MAGI exceeds the threshold above.

“Net investment income” generally includes, per IRS guidance:

• Interest and dividends
• Capital gains (including gain on the sale of a second home or investment property)
• Rental and royalty income
• Non-qualified annuity distributions
• Income from businesses that trade financial instruments or commodities
• Passive income from businesses you don’t materially participate in

It does not include:

• Wages and self-employment income (these can trigger the separate Additional Medicare Tax instead)
• Social Security benefits
• Unemployment compensation
• Alimony
• Distributions from qualified retirement plans like 401(k)s, 403(b)s, and traditional or Roth IRAs
• Tax-exempt municipal bond interest
• Gain on the sale of your primary residence, up to the normal $250,000/$500,000 exclusion

That last point trips people up. If you sell your main home and qualify for the capital gains exclusion, the excluded portion never enters the NIIT calculation at all. Only gain above the exclusion — or gain on a second home or rental property, which gets no exclusion — counts as investment income.

Working Through a Real Example

Take a married couple filing jointly. One spouse earns $180,000 in wages; the other earns $40,000. Combined, they have $30,000 in qualified dividends and $10,000 in long-term capital gains from selling stock.

• Wages: $220,000
• Investment income: $40,000 ($30,000 dividends + $10,000 capital gains)
• MAGI: $260,000

Step 1: Compare MAGI to the threshold.
$260,000 − $250,000 = $10,000 over the threshold.

Step 2: Compare that to net investment income.
Net investment income is $40,000, which is larger than the $10,000 excess.

Step 3: The NIIT applies to the smaller of the two numbers — here, $10,000.

Step 4: Multiply by 3.8%.
$10,000 × 0.038 = $380.

That $380 gets reported on Form 8960 and added to their total tax bill on Form 1040. Notice that even though they had $40,000 in investment income, only $10,000 of it was actually taxed by the NIIT — because that’s how far over the threshold their total income went. If their wages had instead been $260,000 and investment income stayed at $40,000, MAGI would be $300,000, the excess over threshold would be $50,000, and since $40,000 (investment income) is now the smaller figure, the full $40,000 would be taxed: $40,000 × 3.8% = $1,520.

This “lesser of” mechanic is the part people misunderstand most. Having a lot of investment income only matters up to how far your total income actually exceeds the threshold.

How Rental Property and Business Income Fit In

Rental income is a common trigger. If you own a rental property and don’t materially participate in managing it — meaning you’re mostly a passive landlord using a property manager — that net rental income typically counts as investment income for NIIT purposes. If you’re a real estate professional who materially participates under IRS rules, that income may be excluded, but the bar for that classification is specific and documented in IRS Publication 925 on passive activity rules.

Selling a rental property or a business interest can also create a one-time spike. Someone who sells an appreciated rental property for a $150,000 gain may cross the NIIT threshold that single year even though their regular income is otherwise modest — worth planning for if you’re weighing a sale.

How to Actually Calculate and Report It

1. Determine your MAGI (for most filers, this equals AGI from Form 1040 with a few add-backs, such as certain foreign income exclusions).
2. Determine your net investment income by adding up interest, dividends, capital gains, rental/royalty income, and other listed items, then subtracting related expenses (like investment interest expense or state income tax allocable to that income).
3. Complete Form 8960 to calculate the tax — it walks through the “lesser of” comparison automatically.
4. Report the result on Schedule 2 of Form 1040, which flows into your total tax owed.

Because it’s calculated on a separate form, many tax software programs handle it automatically once you’ve entered your investment income correctly. But if you’re doing projections mid-year — for instance, deciding whether to realize a capital gain in December or January — running the Form 8960 math by hand or with a worksheet helps you see whether that timing decision pushes you over the threshold.

FAQ

Does the NIIT replace or add to capital gains tax?

It adds to it. If you sell stock for a long-term gain, you still pay your regular capital gains tax rate (0%, 15%, or 20% depending on income) and then, separately, the 3.8% NIIT applies on top if you’re over the MAGI threshold. The two taxes are calculated independently and both show up on your return.

Are IRA and 401(k) withdrawals subject to NIIT?

No. Distributions from qualified retirement accounts — traditional and Roth IRAs, 401(k)s, 403(b)s, and similar plans — are specifically excluded from net investment income under IRS rules. However, those withdrawals still count toward your MAGI, which can push other investment income (like dividends sitting in a taxable brokerage account) into NIIT territory even though the retirement withdrawal itself isn’t taxed by NIIT.

Can I reduce or avoid the NIIT?

There’s no NIIT-specific deduction, but standard tax-planning moves that lower MAGI or shift income timing can help — contributing to retirement accounts, harvesting capital losses to offset gains, using qualified charitable distributions from IRAs if you’re 70½ or older, or spreading large gains across multiple years. Because these strategies interact with your full tax picture, a tax professional can help model the actual impact for your situation.

Sources

• IRS, “Topic No. 559, Net Investment Income Tax” — https://www.irs.gov/taxtopics/tc559
• IRS, Form 8960 and Instructions — https://www.irs.gov/forms-pubs/about-form-8960
• IRS, “Questions and Answers on the Net Investment Income Tax” — https://www.irs.gov/newsroom/questions-and-answers-on-the-net-investment-income-tax
• IRS Publication 925, Passive Activity and At-Risk Rules — https://www.irs.gov/forms-pubs/about-publication-925

Related reading

• Social Security COLA for 2026: How Much Bigger Will Your Check Be?
• Medicare Open Enrollment: Dates, What You Can Change, and Costly Mistakes
• Medicare Advantage vs Original Medicare: A Plain-English Comparison

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