The Net Investment Income Tax (3.8%)

It applies to the lesser of your net investment income or the amount your modified adjusted gross income exceeds the threshold:

The detail that matters most

Those thresholds have never been indexed for inflation. They were written in 2010, took effect in 2013, and are the same numbers today. Every year of wage growth and every year of asset appreciation pulls more people over a line that has not moved in over a decade.

A one-time sale blows through it instantly. A $2,000,000 gain puts a married couple roughly $1,750,000 over the threshold, and the surtax applies to the full net investment income — about $76,000 on that gain alone, on top of federal capital-gains tax and state tax.

What counts, and what does not

Subject to the 3.8%: capital gains, interest, dividends, rents, royalties, non-qualified annuity income, and income from a passive trade or business.

Not subject to it: wages, self-employment income, active trade or business income where you materially participate, tax-exempt interest, and distributions from IRAs and qualified plans.

That last exclusion is a trap in reverse. IRA and 401(k) distributions are not themselves net investment income — but they raise your modified AGI, which can drag your other investment income over the threshold. The distribution is exempt; it still costs you.

Selling an active business: gain attributable to assets used in a trade or business in which you materially participate is generally outside the surtax. Gain attributable to passive assets, goodwill in a business you did not actively run, and the real estate underneath it usually is not. The allocation matters, and it is worth getting right before closing rather than arguing about it later.

Why this is really an installment-sale question

The surtax is not a rate you can negotiate. It is a threshold you cross or you do not — and thresholds are exactly what spreading income across years is good at.

Recognize $2,000,000 of gain in one year and essentially all of it is over the line. Recognize $200,000 a year across ten years, against modest other income, and a large share of it can sit under the threshold entirely — not taxed at 3.8%, not because of any structure the IRS dislikes, but because the income was never in one year to begin with.

This is the quietest argument for an installment sale and usually the one nobody makes. The capital-gains bracket spreading is visible. The surtax that simply never applies is invisible, and on a large sale it is often the larger number of the two.

Both our capital gains exit calculator and the seller financing calculator compute the 3.8% year by year, so you can see which years it applies to and which years it does not.

What actually reduces it

• Spread the gain. An installment sale keeps more years under the threshold. This is the main lever on a large one-time sale.
• Establish material participation before the sale, where it is genuinely true, so more of the gain is active-business gain.
• Harvest losses in the year of sale — capital losses reduce net investment income directly.
• Charitable structures, including a charitable remainder trust, remove gain from the calculation, at the cost of the remainder.
• Watch the interaction with retirement distributions. Taking a large IRA distribution in the year of a sale can push otherwise-untaxed investment income over the line.

What does not work: moving to a no-income-tax state. The surtax is federal. Nevada and Texas do not help you here.

Frequently asked

Q: Is the net investment income tax the same as the Medicare surtax? A: They are two different 0.9% and 3.8% provisions from the same 2010 legislation. The 0.9% additional Medicare tax applies to wages and self-employment income. The 3.8% net investment income tax applies to investment income. You can owe both in a year, on different income.

Q: Do I pay 3.8% on the whole sale price? A: No — on the gain, and only to the extent your modified AGI exceeds the threshold. If your MAGI is $300,000 as a married couple, only $50,000 is exposed regardless of how large your investment income is.

Q: Does an S-corporation shield me? A: Only if you materially participate. Passive S-corp income is net investment income. Active income is not.

Q: Are the thresholds ever going to be adjusted? A: They have not been since enactment, and no adjustment mechanism exists in the statute. Plan on the numbers above.

Q: Does the 3.8% apply to a primary residence sale? A: Only to gain above the §121 exclusion. Excluded gain is not investment income.