The 3.8% Net Investment Income Tax on a Big Sale

How it works, in plain English

Since 2013, IRC 1411 adds a 3.8% tax on investment income for higher-income households. The math is a lesser-of test: take your net investment income, take your modified adjusted gross income minus the threshold, and pay 3.8% of the smaller number. The thresholds are written into the statute ($250,000 married filing jointly, $125,000 married filing separately, $200,000 for everyone else) and have never been adjusted for inflation, so each year more sellers cross them.

A big sale crosses them easily. A couple with $150,000 of wages who sells a rental for a $1,000,000 gain has $1,150,000 of MAGI. The excess over $250,000 is $900,000, smaller than the $1,000,000 of investment income, so the tax is 3.8% of $900,000. The tax is computed on Form 8960 and added to your Form 1040. It is federal only, applies on top of regular capital gains tax and depreciation recapture, and cannot be reduced by the standard deduction.

What counts as net investment income on a sale

Section 1411(c) lists three buckets: interest, dividends, rents and similar income; income from a passive business or a trading business; and net gain from selling property, except property held in a non-passive trade or business. For a big sale, that means:

Reg. 1.1411-4 adds a timing rule that matters for seller financing: whether installment gain is investment income is decided in the year of sale and carries through every later payment. Retiring after closing does not convert the later gain.

Material participation and the Section 1411(c)(4) exception

The business exception turns on Section 469 material participation, tested under seven tests in Temp. Treas. Reg. 1.469-5T(a). The common ones: more than 500 hours in the activity this year, or material participation in any five of the last ten years, or (for a personal service business) any three prior years. The five-of-ten rule is what protects many owners who stepped back before selling.

For an interest in a partnership, LLC taxed as a partnership, or S corporation, Section 1411(c)(4) limits NII to the gain you would have had if the entity sold all its property at fair market value, counting only property that is not held in a non-passive trade or business. In practice an active owner pays NIIT only on the slice tied to investment assets, such as excess cash or a building the entity leases out. The final regulations reserve Section 1.1411-7 for the detailed rules; the IRS proposed look-through rules in 2013 that are not final, so your CPA applies the statute and the proposed method with care.

Self-rental. If you rent a building to a business you materially participate in, the self-rental rule makes the net rent non-passive, and Reg. 1.1411-4(g)(6) then keeps that rent outside NII. Gain on selling the building is outside NII only to the extent the passive rules treat it as non-passive, most clearly when the building was properly grouped with the business under Reg. 1.469-4(d)(1). This matters when an owner sells the operating company and the real estate together.

Rental real estate professionals

Rental income and rental gain are investment income for most landlords, even busy ones, because rental activity is passive by default. The exception is the real estate professional under Section 469(c)(7): more than half of your working hours and more than 750 hours a year in real property businesses where you materially participate. Reg. 1.1411-4(g)(7) then adds a safe harbor: if you participate in a rental activity more than 500 hours that year, or more than 500 hours in any five of the prior ten years, rents and gain on property used in that rental activity are treated as business income, outside NII. An election to group all rentals as one activity applies here too. Keep time logs; this is one of the most audited claims in the code.

Worked example (engine-computed)

Assumptions (labeled, not a quote): married filing jointly, Texas residents (no state income tax), $150,000 of wages every year, 2026 federal tables held flat in later years, a $1,000,000 long-term gain on a rental held as investors. Note interest is left out to isolate the gain; real interest would add investment income.

Spreading did two things here. It moved most of the gain from the 20% rate into the 15% bracket, and it cut the NIIT base from $900,000 to the amount each year's income ran over $250,000. With ten years of $100,000, income sat exactly at the threshold and the NIIT disappeared. The calculation ignores the time value of money and the buyer's interest, both of which the full analysis includes. Run your numbers to see your own year-by-year schedule.

Planning moves that shrink it

• Spread the gain. An installment sale keeps each year's MAGI closer to the threshold. See the basics of installment sale tax and seller financing taxes. Remember that note interest is itself investment income.
• Document participation. If you ran the business in five of the last ten years, you may already be outside NII on an active entity interest.
• Check the real estate. A building rented to your own active business, and grouped with it, can be outside NII; a pure investment property is not.
• Use losses. Capital losses, suspended passive losses released on the sale (Section 469(g)) and properly allocable deductions reduce net investment income. See tax-loss harvesting.
• Time the year. A year with low wages or a closing split across December and January can keep MAGI down. See year-end timing.
• Defer it entirely. A 1031 exchange defers the gain, so there is nothing to subject to NIIT that year.

Trusts hit the threshold almost immediately

A non-grantor trust or estate pays NIIT on the lesser of its undistributed net investment income or its AGI over the dollar amount where the top trust bracket begins (IRC 1411(a)(2)). For 2026 that is $16,000 (Rev. Proc. 2025-32). A trust that keeps a large capital gain pays 3.8% on almost all of it. Distributions to beneficiaries can move NII to their returns, where their own $200,000 or $250,000 threshold applies, but capital gains usually stay in the trust unless the trust document or local law allows them to be distributed. A grantor trust, including a revocable living trust, is ignored: the grantor reports the sale. See grantor vs non-grantor trust.

IRS stance, costs, and how it compares with a Section 453 installment sale

The IRS treats NIIT as settled: final regulations since 2013, Form 8960 every year, and frequent exam focus on material participation, real estate professional claims and grouping elections. There are no special fees; the cost is CPA time to document participation and allocate gain. An installment sale does not change whether gain is investment income (that is fixed in the year of sale), but it can lower how much is taxed, by keeping more years at or under the threshold. The trade is waiting for your money and carrying buyer credit risk, managed with a solid down payment, security and strong note terms. Get the full Big Sale Tax Analysis to see NIIT modeled year by year next to a cash sale, a 1031 and the other paths.

Get the full Big Sale Tax Analysis

Frequently asked questions