STR + cost segregation: how the loophole pairs up

By Tom, CPA · Updated October 27, 2026

Part of: Rental Property Taxes

TL;DR: A short-term rental with an average guest stay of 7 days or less is not a rental activity under the passive loss rules. If you also materially participate, a cost segregation study plus 100% bonus depreciation (for property acquired after Jan. 19, 2025) can create a large loss that offsets wages. The price is airtight records now and depreciation recapture later.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

CPA Warning Label: Paper losses need real logs. If your hours or stay data fail, the loss is passive; if they pass, you still owe recapture, partly at ordinary rates, when you sell.

How the combo works

Two independent rules have to line up, and people who sell courses tend to mention only the fun one.

1. The activity test. Under Treas. Reg. 1.469-1T(e)(3)(ii), an activity is not a "rental activity" if the average period of customer use is 7 days or less (or 30 days or less with significant personal services). That takes the STR out of the rule that makes rentals automatically passive. See the short-term rental loophole guide for the full test.
2. The participation test. Once it is not a rental activity, it is treated like any other business: passive unless you materially participate under one of the seven tests in Reg. 1.469-5T. Covered in the seven material participation tests.
3. The loss generator. A cost segregation study reclassifies parts of the building from 39-year (STRs with average stays of 30 days or less are generally treated as nonresidential real property, not 27.5-year residential) into 5-, 7- and 15-year property, which is eligible for bonus depreciation.

Pass all three and the first-year loss is non-passive. Non-passive losses can offset wages, business income and portfolio income, subject to the excess business loss limit under section 461(l). Fail the first two and you still get the depreciation; it just sits in the passive bucket as a suspended loss until you have passive income or sell.

One recovery-period nuance worth flagging: residential rental property is a building where 80% or more of gross rents come from dwelling units, and Pub. 946 treats units used on a transient basis (more than half of units for stays under 30 days) as not dwelling units. That is why many STR studies use 39 years for the building remainder. Confirm with your study provider.

Material participation needed

This is where most STR loss claims die in an audit: not on the math, on the hours. The tests most STR owners use:

• Test 3: more than 100 hours in the year and not less than anyone else, including your cleaner, handyman and co-host individually.
• Test 1: more than 500 hours in the year.
• Test 2: your participation is substantially all of the participation by everyone, which rarely works if you have a cleaner.

Hours have to be your own work in the activity: guest communication, cleaning, repairs, restocking, listing management, booking oversight. Investor-type hours (reading statements, researching the market) generally do not count unless you are directly involved in day-to-day management. A spouse's hours count toward material participation, even if the spouse is not on title (Reg. 1.469-5T(f)(3)).

The timing trap: the study is usually done the year you buy, which is also the year you are still learning the property. If you hire a full-service property manager, test 3 becomes very hard, because the manager almost certainly logged more hours than you. Keep a contemporaneous log. Calendar entries, message timestamps and receipts beat a spreadsheet reconstructed in April. Our time log guide shows a format that holds up.

Bonus depreciation rate today

As of Oct 2026, the One Big Beautiful Bill Act made 100% additional first-year depreciation permanent for qualified property acquired after January 19, 2025, per IRS IR-2026-06 and Notice 2026-11. Property acquired under a binding written contract before that date stays under the old phase-down, which was 40% for property placed in service in 2025. For a taxpayer's first year ending after Jan. 19, 2025, there is also an election to use 40% instead of 100%.

Section 179 is a different tool. It is generally not available for property used predominantly to furnish lodging (section 50(b)(2)), with an exception for transient lodging facilities. Bonus avoids that question entirely, which is why STR studies lean on it. See bonus depreciation for rental property and section 179 for rentals.

Recapture later

The first-year deduction is a loan from your future self at an interest rate of zero, payable on sale. When you sell:

• 5-, 7- and 15-year components are section 1245 property. Gain up to the depreciation taken is recaptured as ordinary income, at your marginal rate, not a capital gains rate.
• The building produces unrecaptured section 1250 gain, taxed at up to 25%.
• Anything left is long-term capital gain, and possibly 3.8% NIIT.

Much of the personal property value is gone by the time you sell (worn-out couches are worth what the next buyer pays for them, which is little), and gain is allocated by component value at sale. A good study supports a lower allocation to tired furnishings at sale, which limits 1245 recapture. But don't count on that magic: the purchase agreement and appraisal should support the allocation. Details in depreciation recapture on rental property.

Deferral options exist: a 1031 exchange into another property carries the deferred recapture forward, and dying with the property gets a basis step-up under current law. Neither is free; both change your choices for decades.

Realistic examples

Illustration (made-up numbers): Lavish Larry earns $300,000 in W-2 wages and buys a mountain cabin in March 2026 for $800,000, with $160,000 allocated to land. The $640,000 depreciable basis gets a study that assigns 25% to 5-, 7- and 15-year property: $160,000.

If Larry materially participates and the average stay is under 7 days, the loss offsets wages. At a 35% marginal rate that is roughly $52,000 of federal tax deferred, before state tax and before the excess business loss limit (which, for 2026, could bite on a loss this size only if he has other business losses; check the current-year threshold). The study might cost a few thousand dollars.

Now the same cabin with a property manager doing 300 hours while Larry does 80: he fails test 3, the loss is passive, and it sits suspended. Same depreciation, zero current benefit. Frugal Fran, meanwhile, is the one who reads the log requirements before buying.

Sale illustration: Larry sells in 2032 for $950,000. The $160,000 of bonus property, if it still has value at sale, is recaptured first at ordinary rates to the extent of gain allocated to it; building depreciation is taxed at up to 25%. Run the numbers with the cost seg savings calculator and the depreciation recapture calculator.

Who this pairing actually fits

It tends to work for people with high ordinary income who will truly self-manage, who have a multi-year hold, and who buy a property that pencils without the tax benefit. It works badly when the deal only makes sense because of the deduction, when the owner lives far away and relies on a full-service manager, or when you will sell within a couple of years and hand most of the savings back. Read our when a cost seg study is worth it and Schedule C vs Schedule E for STRs before signing anything, because substantial services can also move the income onto Schedule C with self-employment tax.