Cost Segregation and Passive Loss Limits: Who Can Use the Deduction

A cost segregation study can create a large first-year loss, but whether you can deduct it against wages and other ordinary income depends on the passive activity loss rules. Rental activities are passive by default. Unless you qualify as a real estate professional, run a qualifying short-term rental, or fall under the $25,000 special allowance (which phases out between $100,000 and $150,000 of modified adjusted gross income), the loss is generally suspended and carried forward instead of reducing this year's tax.

That is the surprise many investors get after ordering a study for the big first-year deduction. Their CPA runs Form 8582 and most of the loss turns out to be suspended. With about eight weeks left in 2026, this guide explains the rules, works through two hypothetical examples, and gives a framework for deciding whether a study still makes sense. This is general education, not tax advice. Confirm how these rules apply to you with your CPA.

How a Cost Segregation Study Creates a Paper Loss

A cost segregation study separates a building's purchase price into components with different tax lives. Instead of depreciating everything over 27.5 years (residential rental) or 39 years (nonresidential), the study identifies 5-, 7-, and 15-year property, such as flooring, certain fixtures, and land improvements.

Short-life property can qualify for bonus depreciation. Under the One Big Beautiful Bill Act (OBBBA), 100% bonus depreciation applies to qualifying property acquired after January 19, 2025. Our guide to 100% bonus depreciation in 2026 covers the details. The result can be a first-year depreciation deduction far larger than the rental's cash income, which produces a paper loss: a tax loss with no matching cash loss.

Bonus depreciation makes the loss bigger. It does not make the loss usable. Whether you can deduct it this year is a separate question, answered by the passive activity rules.

Rentals Are Passive by Default

Under the passive activity rules, losses from a passive activity generally can offset only passive income, not wages, business profits, interest, or dividends. According to IRS Publication 925, a rental activity is passive even if you materially participate in it, unless you materially participated as a real estate professional.

In practice, a W-2 employee with a rental property starts from this position: the rental loss can offset passive income, such as profit from another rental, but not their salary. Three routes can change that outcome:

The $25,000 Special Allowance

Per IRS Publication 925, if you or your spouse actively participated in a passive rental real estate activity, you can deduct up to $25,000 of loss from that activity against nonpassive income, such as wages.

What counts as active participation

Active participation is a lower bar than material participation. The IRS says it can include approving new tenants, deciding rental terms, and approving capital or repair expenditures. You can use a property manager while still making these decisions.

Two disqualifiers to know about:

• Less than 10% ownership. An interest of less than 10% (by value) in the activity means no active participation.
• Limited partners. Limited partners are generally not treated as actively participating.

The MAGI phase-out

The allowance shrinks as income rises. Per Publication 925 and the Instructions for Form 8582:

• The allowance is reduced by 50% of MAGI above $100,000.
• It is generally zero at $150,000 or more of MAGI.
• For married filing separately and living apart all year, the figures are halved: $12,500 allowance, phase-out starting at $50,000, and zero at $75,000.
• If you file separately and lived with your spouse at any time during the year, no allowance is available.

MAGI here is a specific calculation made on Form 8582, and it is not the same as the AGI line on your return. Have your CPA compute it.

The allowance is an annual cap on total loss from your passive rental real estate, not a per-property amount. A second rental doesn't give you a second $25,000.

Hypothetical Example 1: $120,000 MAGI

The numbers below are hypothetical and for illustration only.

A single filer with $120,000 of MAGI actively participates in one rental. A cost segregation study plus 100% bonus depreciation produces a $90,000 net rental loss in year one.

MAGI exceeds $100,000 by $20,000.

The allowance is reduced by 50% of that excess: $10,000.

The allowance is $25,000 − $10,000 = $15,000.

This matches the math in IRS Publication 925's own example, which uses a $120,000 salary and a $31,000 rental loss to arrive at a $15,000 allowance. Here the loss is much larger, so the allowance is the binding limit and $75,000 carries forward.

Hypothetical Example 2: $160,000 MAGI

Also hypothetical.

Same property, same $90,000 loss, but the investor's MAGI is $160,000. Because MAGI is above $150,000, the special allowance is $0.

Unless the investor has other passive income to absorb the loss, or qualifies as a real estate professional or short-term rental operator, none of the first-year deduction reduces 2026 tax. The depreciation isn't lost. It is deferred.

Route 1: Real Estate Professional Status

A taxpayer who qualifies as a real estate professional can treat rental activities as nonpassive, but only if they also materially participate in the rental activity. Qualifying is demanding. It involves hours tests tied to real property trades or businesses, and both must be met in the same tax year. For married couples, the rules about whose hours count are strict.

REPS is also among the more heavily scrutinized positions, and documentation is what carries it. Our detailed guide, Real Estate Professional Status and Cost Segregation, covers the two tests, the material participation requirement, the grouping election, and how to keep a defensible time log. If you plan to qualify, the log should start now, not at tax time.

Route 2: The Short-Term Rental Route

Some investors reach nonpassive treatment through short-term rentals rather than REPS. When the average guest stay is 7 days or less, the property generally isn't treated as a "rental activity" under the passive loss rules. It is tested like an ordinary business instead. If you materially participate, the losses can be nonpassive and usable against W-2 income.

The most common material participation test used by hosts is more than 100 hours on the activity, and more than any other individual. Hosts who use managers or co-hosts should watch that last part, because outside help can push someone else's hours above yours.

Personal use of the property can also affect the analysis. Our guides on cost segregation for Airbnb and short-term rentals and a short-term rental cost segregation example walk through the mechanics and a worked case.

This route is often called a "loophole," but it is a defined rule with tests that must be met and documented.

What Happens to Suspended Losses

Suspended passive losses aren't forfeited. In general terms:

• They carry forward to future years, with no expiration date under the general rules.
• They can offset future passive income, including income from the same property once it is profitable, or from other passive activities.
• They can be released on a fully taxable disposition. Generally, when you dispose of your entire interest in the activity in a fully taxable transaction (to an unrelated party, for example), the suspended losses from that activity can be used against other income. Details and exceptions apply, and transfers such as gifts, related-party sales, and like-kind exchanges are treated differently. Ask your CPA how your exit plan interacts with suspended losses.

Also keep in mind that accelerated depreciation can come back as depreciation recapture when you sell.

When a Study Still Makes Sense Even if the Loss Is Suspended

A suspended loss isn't automatically a wasted study. Consider one when:

• You have passive income elsewhere. Profit from other rentals or passive investments can absorb the loss. Your CPA can model this on Form 8582.
• You plan to sell. A fully taxable sale can release suspended losses, though recapture is part of the same picture.
• You qualify, or expect to qualify, as a real estate professional. Timing a study with your qualifying year can make the loss usable.
• You operate a qualifying short-term rental. With material participation documented, the loss may be nonpassive.
• You have a long hold and expect your income to fall. If MAGI drops in a later year, more of the carryforward becomes usable under the allowance.

When It May Be Smarter to Wait

• Your MAGI is above $150,000, you're a W-2 earner, and you have no passive income and no REPS or STR route. Paying for a study purely for a deduction you can't use this year is hard to justify.
• Your records for material participation don't exist yet. Start the log first.

Waiting doesn't mean giving up the deduction. A look-back cost segregation study can be done on property you already own, with the catch-up depreciation claimed through a change in accounting method on Form 3115. That gives you flexibility to time the deduction for a year when you can use it. Whether it fits your situation is a question for your CPA.

Year-End Checklist: What to Do This Week

Confirm the placed-in-service date. The property must be ready and available for rent by December 31. See our year-end tax planning guide.

Estimate your 2026 MAGI. Where you land relative to $100,000 and $150,000 sets your special allowance.

Ask your CPA to model Form 8582. Have them show the usable loss, the suspended loss, and the tax impact with and without a study.

Confirm active participation. Make sure you or your spouse approve tenants, set terms, and approve repairs, and that you meet the 10% ownership threshold.

Gather material participation records. If you're relying on REPS or the short-term rental route, you need a contemporaneous log of dates, tasks, and hours, plus the average guest-stay data for each STR.

Order the study with timing in mind. The report needs to be ready before your preparer files, and your CPA needs it early enough to model the return.

Frequently Asked Questions

Can I deduct cost segregation against W-2 income?

Only if the loss is nonpassive or covered by the special allowance. A W-2 earner with MAGI up to $100,000 and active participation can generally use up to $25,000 of rental loss. Between $100,000 and $150,000 the allowance phases out, and above $150,000 it is generally zero. Real estate professionals who materially participate and qualifying short-term rental operators can potentially deduct more.

Does 100% bonus depreciation override the passive loss rules?

No. Bonus depreciation increases the size of the deduction, but the passive activity rules decide whether you can use it against nonpassive income. A bigger first-year loss can mean a bigger suspended loss.

Are suspended passive losses ever lost?

Generally no. They carry forward and can offset future passive income, and they can generally be released on a fully taxable disposition of your entire interest in the activity. Rules and exceptions apply, so confirm with your CPA.

Do I need to be a real estate professional to use the short-term rental route?

No. The short-term rental route is separate from REPS. It depends on an average guest stay of 7 days or less and on material participation in the activity.

If my loss is suspended, should I skip the study?

Not necessarily, but it changes the calculus. The deduction is deferred, not erased, and it can still be valuable if you have passive income, plan to sell, or expect to qualify for REPS or STR treatment. If none of those apply, it can be reasonable to wait.

The Bottom Line

A cost segregation study makes the depreciation bigger and bonus depreciation can accelerate it, but the passive activity rules decide who can use it. Active participants with MAGI under $100,000 can use up to $25,000, the allowance phases out to zero at $150,000, and everyone else generally needs real estate professional status, a qualifying short-term rental, or passive income to absorb the loss. Before you order a study, ask your CPA what Form 8582 will show.

This article is general education, not tax advice. Passive activity rules, the special allowance, material participation, and the treatment of suspended losses depend on your specific facts. The figures in the examples are hypothetical. Confirm everything with a qualified CPA before you act.

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ROOM42 prepares engineering-based cost segregation studies for residential and commercial investors, including look-back studies for properties you already own. Get your free estimate and see what your 2026 return could look like, with no credit card required.