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Yes, the 3.8 percent net investment income tax (NIIT) can apply to your rental income and to the gain when you sell a rental property, and a cost segregation study can change how much of it you pay. It does not work the same way for every owner. A passive landlord with a high income, a short-term rental host who materially participates, a real estate professional, and a limited partner in a syndication can each end up in a different place with the same building and the same study. And the depreciation that lowers the tax while you hold the building comes back as gain when you sell, with the NIIT on top of it for a passive owner.
Rosa is an engineer in Charleston, West Virginia, single, with about $300,000 of income. In March 2025 she bought a small apartment building for $1,500,000, had it ready for tenants in April, and asked her CPA one question before ordering a cost segregation study: would the study change the 3.8 percent tax she had started paying on her dividends? The CPA's answer ran three ways. It would lower the tax a little while she held the building, it would do nothing for the part of her return the building does not touch, and it would raise the tax in the year she sold. Her numbers run through the sale example below. Rosa is illustrative; the rules are real.
The NIIT is a separate tax from regular income tax, imposed by Section 1411 since 2013. For an individual, it equals 3.8 percent of the smaller of two numbers: your net investment income for the year, or the amount by which your modified adjusted gross income exceeds the threshold for your filing status. The thresholds are $250,000 for married filing jointly, $200,000 for single and head of household, and $125,000 for married filing separately. They do not adjust for inflation, so more owners cross them every year. You report the tax on Form 8960.
If your income is far above the threshold and your investment income is small, the tax is 3.8 percent of the investment income. If your investment income is large and your income is only slightly above the threshold, the tax is 3.8 percent of the excess. Net investment income includes interest, dividends, annuities, royalties, capital gains, and rents, along with income from a passive trade or business. Wages, self-employment income, and income from a nonpassive trade or business are outside it. The NIIT sits on top of regular income tax and on top of the rates on capital gains and depreciation recapture, which is why a sale year can be expensive.
Section 1411 treats rents and gains from disposing of property as investment income, with one exception: income from a nonpassive trade or business under Section 469. That exception has two parts, and both have to be satisfied.
Is the rental a trade or business? The preamble to the final regulations points to Section 162 and the case law, under which an activity needs to be conducted with regularity and continuity for profit. A single-family home on a long-term lease with a property manager handling everything may or may not reach that level. A portfolio of apartments with active management often does.
Is it nonpassive for you? Under Section 469, a rental activity is passive by definition unless you qualify as a real estate professional and materially participate, or unless the activity is not treated as a rental activity at all. The most important exception to the rental definition is the short-term rental rule. Under Treasury Regulation 1.469-1T(e)(3)(ii), an activity is not a rental activity if the average period of customer use is seven days or less, or 30 days or less when significant personal services are provided. When an activity falls outside the rental definition and you materially participate in it, the activity is nonpassive, and that is the foundation of the strategy we explain in how the short-term rental loophole works with cost segregation. Material participation is tested by the seven tests in the regulations. The same facts that make a rental nonpassive for the loss rules are usually the facts that keep the income out of net investment income.
A cost segregation study is a fully engineered and accounted analysis that separates the components of a building from the structure, so that items such as removable flooring, specialty electrical, landscaping, paving, and site utilities are depreciated over 5, 7, or 15 years instead of 27.5 or 39. For qualifying property acquired and placed in service after January 19, 2025, 100 percent bonus depreciation lets that short-life property be deducted in the year it is placed in service.
For a rental in the NIIT base, net rental income is gross rents minus properly allocable deductions, and depreciation is one of them. A larger first-year deduction means smaller net rental income and a smaller NIIT, and it can lower modified adjusted gross income as well. The limit is the passive activity loss rule. Depreciation can reduce a passive rental's net income to zero, but it cannot create a loss you deduct against wages. The excess is suspended and carried forward. So for a passive owner, cost segregation can wipe out the rental's own contribution to net investment income, but it does not shelter the rest of the return.
Dana and Chris file jointly. Dana earns $340,000 in wages, and Chris is a stay-at-home parent. They own a small apartment building through an LLC, a management company handles everything, and they do not meet the hours tests. The building produces $50,000 of net rental income before depreciation, and they have another $30,000 of interest and dividends. The numbers are illustrative.
Before a study, their modified adjusted gross income is $420,000 ($340,000 wages plus $50,000 rental plus $30,000 investment income). Their net investment income is $80,000. The excess of income over the $250,000 threshold is $170,000. The NIIT is 3.8 percent of the lesser of $80,000 and $170,000, which is $3,040.
Now suppose a cost segregation study generates an additional $60,000 of first-year depreciation. The rental's own net income falls from $50,000 to zero, and the remaining $10,000 of loss is suspended, because Dana and Chris earn too much to use the $25,000 special allowance for active participation, which phases out between $100,000 and $150,000 of modified adjusted gross income. Their modified adjusted gross income falls to $370,000, and their net investment income falls to $30,000. The excess over the threshold is $120,000. The NIIT is 3.8 percent of the lesser of $30,000 and $120,000, which is $1,140.
The NIIT dropped by $1,900 in the study year, a modest slice of the total value, which is mostly the regular income tax on the $50,000 of rental income that no longer shows up on the return. The depreciation they took early comes back as gain if they sell.
If the average stay is seven days or less and you materially participate, the activity is nonpassive. If it is also a Section 162 trade or business, which a hosted short-term rental run with regularity for profit usually is, the net income is outside net investment income, and Form 8960 lets you exclude it.
Nell and Owen file jointly. Nell earns $390,000 in wages as a software executive. Owen manages a short-term rental cabin the couple bought in March 2025 and had ready for guests that spring. The average guest stay is about four days, and Owen spends 650 logged hours on bookings, guests, supplies, and maintenance. The cabin earns $70,000 before depreciation. They also have $20,000 of interest and dividends.
Because the stays are short and Owen materially participates, the cabin is nonpassive, and its income is outside net investment income. Their net investment income is $20,000 whether or not a study is performed. Before a study, their modified adjusted gross income is $480,000; the NIIT is 3.8 percent of the lesser of $20,000 and $230,000, which is $760. A study that produces $180,000 of first-year depreciation turns the cabin's $70,000 of income into a $110,000 loss, which can offset Nell's wages if the other limits allow; their $110,000 loss sits under the Section 461(l) excess business loss cap for 2025, $626,000 for joint filers ($313,000 single), adjusted annually, which we cover in the excess business loss limit. Their modified adjusted gross income drops to $300,000, and the NIIT is 3.8 percent of the lesser of $20,000 and $50,000, which is again $760.
The NIIT outcome did not change, because the cabin was never in the NIIT base. The benefit here is in regular income tax, where the loss offsets wages. The same study produces a different kind of benefit for Dana and Chris than for Nell and Owen, which is why you need to know which bucket you are in before you evaluate a study.
A real estate professional must spend more than half of their personal service time, and more than 750 hours, in real property trades or businesses in which they materially participate, and must materially participate in the rentals for the losses to be nonpassive. For the NIIT, the analysis is applied rental by rental. In the preamble to the final regulations, Treasury declined to adopt real estate professional status as a proxy for the trade or business exception and instead provided a safe harbor in Treasury Regulation 1.1411-4(g)(7). Under it, rental income and gain are treated as derived in a trade or business if you participate in the rental activity for more than 500 hours during the year, or if you participated for more than 500 hours in five of the ten preceding years. If you fall short of the safe harbor, you may still be able to establish that the rental is a Section 162 trade or business on the facts, but the more of your portfolio is managed by third parties, the harder that argument becomes. Grouping matters here too, because how rentals are grouped affects the hours counted for each activity. We cover the mechanics in The Grouping Election and the interaction with cost segregation in Real Estate Professional Status Is Step One.
Picture Alicia, a real estate professional who works 1,400 hours a year on a self-managed portfolio that meets the safe harbor on a grouped basis, and who also owns a triple-net retail building across the country where she spends 15 hours a year. Whether that building's income is in net investment income depends on how the rentals are grouped and on the facts. A CPA who treats her status as a blanket exemption could understate the NIIT.
A limited partner in a syndication is presumed under Section 469(h)(2) not to materially participate, so K-1 rental income is passive and included in net investment income. A study performed by the partnership reduces that income, and in the early years often produces a K-1 loss that is suspended, though it can offset passive income from other sources.
Gain on the sale of a passive rental is net investment income. Gain on property held in a nonpassive trade or business is generally excluded, except for the portion attributable to working capital. Your adjusted basis at sale is your cost minus the depreciation allowed or allowable, so accelerated depreciation means a larger gain at a given sale price. Gain attributable to depreciation on the 5- and 7-year components is taxed as ordinary income under Section 1245 up to the depreciation taken. Gain attributable to depreciation on real property is taxed under Section 1250, with unrecaptured Section 1250 gain subject to a maximum 25 percent rate. The NIIT applies on top of those rates for owners whose gain is net investment income. See Cost Segregation and Depreciation Recapture: What Really Happens When You Sell.
Back to Rosa, single, with a modified adjusted gross income of about $300,000 before the sale. Her Charleston building cost $1,500,000 in March 2025, of which $1,200,000 is allocable to the building and $300,000 to land, and it was ready and available for tenants in April 2025. The example is illustrative, uses the IRS mid-month table rate for April (2.576 percent for 27.5-year property) in year one and full-year depreciation after that, and ignores suspended losses to isolate the effect on the sale.
With a study, assume $300,000 of the building cost is reclassified to short-life property and deducted in year one under 100 percent bonus depreciation, and the remaining $900,000 is depreciated over 27.5 years: $23,184 in year one at the April table rate, then $32,727 in each of years two and three. After three years she has taken $388,638 of depreciation. Without a study, the full $1,200,000 is depreciated over 27.5 years: $30,912 in year one, then $43,636 in each of years two and three, or $118,184 after three years.
She sells at the end of year three for a net amount realized of $1,850,000. With the study, her adjusted basis is $1,500,000 minus $388,638, or $1,111,362, and her gain is $738,638. Without the study, her adjusted basis is $1,500,000 minus $118,184, or $1,381,816, and her gain is $468,184. If the whole gain is net investment income and her income is well above the $200,000 threshold, the NIIT is 3.8 percent of $738,638, or $28,068, with the study, versus 3.8 percent of $468,184, or $17,791, without it. The difference is $10,277 of additional NIIT at the sale.
That number needs context. The additional $270,454 of gain is the same $270,454 of extra depreciation she deducted early, in year one, against income taxed at her ordinary rates. A real analysis also accounts for the time value of the money saved, the character of the gain, and suspended losses released on a fully taxable disposition. Cost segregation can still be a good trade at sale. The NIIT belongs in the full picture.
A Section 1031 exchange defers gain, and the NIIT on it, while the replacement property is held; see 1031 Exchanges and Cost Segregation. Suspended passive losses, including those created by a study, are released on a fully taxable disposition to an unrelated party and reduce the gain; see The Deduction You Could Not Use Finally Comes Loose. Holding until death eliminates the recapture through the basis adjustment. And a nonpassive owner's gain may be excluded from the NIIT in the first place.
Every number in this article starts with the depreciation figure. The IRS Cost Segregation Audit Techniques Guide describes six common approaches. A fully engineered and accounted study works under the first two: detailed engineering from actual cost records, or engineering with documented estimates reconciled to actual cost. Each component is identified, costed, and assigned to its recovery period, and the result is a component schedule your CPA imports and an examiner can trace line by line, signed by credentialed professionals, and defended for as long as you own the building. The estimated study hands your CPA a percentage, and on a Form 8960 question or a sale-year examination, a percentage has nothing behind it.
Assuming real estate professional status means no NIIT. The safe harbor and the facts control. Rely on the label and you can underpay, with penalties and interest; ignore the exclusion and you overpay.
Forgetting the NIIT in the sale year. Many owners model income tax and recapture and then discover an additional 3.8 percent on the entire gain. On a large sale, that is a five- or six-figure item.
Treating a suspended loss as a lost deduction. Passive losses carry forward and offset passive income or come loose on a qualifying sale.
Not keeping contemporaneous records. If your position depends on hours, the IRS can ask you to prove them. A calendar, a booking report, and a time log kept as you go are far more persuasive than a reconstruction made during an audit.
Choosing a study based on price instead of quality. The deduction is only as good as the study that supports it, and the sale-year gain calculation depends on the same component schedule. A thin report leaves your CPA guessing on both ends.
A study needs at least $180,000 of depreciable basis after land to be worth the fee. If you are a passive owner whose rental already shows little or no net income, the NIIT saving in the study year is close to zero and the deduction sits suspended until you have passive income or sell, so the fee buys a carryforward rather than cash. If a sale is planned within a couple of years, the larger gain, the ordinary-income recapture on the 5- and 7-year property, and the NIIT on top of it can outweigh the time value of the early deduction. And if your modified adjusted gross income sits below the threshold in every year including the sale year, the NIIT is not part of the decision at all, and the study stands or falls on regular income tax alone.
The rate is 3.8 percent. It applies to the lesser of your net investment income or the amount by which your modified adjusted gross income exceeds $250,000 for married couples filing jointly, $200,000 for single and head of household filers, or $125,000 for married filing separately.
It can. Rents are net investment income unless they come from a trade or business that is nonpassive for you. A passive long-term rental is included. A short-term rental in which you materially participate, or a rental trade or business in which you are nonpassive, is excluded.
Not automatically. The NIIT turns on whether the rental income is derived from a trade or business that is nonpassive for you. The regulations provide a safe harbor based on 500 hours of participation in the rental activity, and many real estate professionals qualify under it.
Gain from a passive rental is net investment income; Rosa's $738,638 gain in the sale example carries $28,068 of it. Gain from property held in a nonpassive trade or business is generally excluded. A Section 1031 exchange defers the gain, and the NIIT on it, until the replacement property is sold in a taxable transaction.
Often, yes. Depreciation can eliminate the rental's own taxable income, and any excess is suspended and carried forward to offset future passive income or released on a qualifying sale. Whether the economics work depends on the size of the deduction against the cost of the study and your ability to use it over time.
It can, to the extent the extra depreciation is deductible in the year. A nonpassive owner's loss reduces adjusted gross income directly. A passive owner's deduction stops at the rental's own income unless passive income or the $25,000 allowance absorbs the rest.
Work out which bucket you are in first, with your CPA. Then send Jim Dougherty and his team at Cost Seg America your closing statement and a few photos. You will have a free proposal within 24 hours showing the likely first-year deduction, so your CPA can model the regular tax, the NIIT, and the carryforward before you commit, the way Rosa's CPA modeled her sale year before she ordered. Every study is fully engineered and accounted, signed, and defended for as long as you own the building, with no time limit, no hour cap, and no additional fee. Call 1-888-365-5023 or email info@costsegamerica.com.
This article is for general educational purposes and does not constitute tax, legal, or accounting advice; the examples are illustrative with simplified assumptions, and you should confirm current requirements with your CPA before making any tax decision.
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