VaultSTROur take
The “STR loophole” is real, widely used, and badly explained by almost everyone selling something. Here is the plain version: the passive-activity rules that normally trap rental losses do not treat a short-term rental as a rental when average guest stays run seven days or less. Clear that bar, materially participate in the operation, and the property’s paper losses — driven mostly by depreciation — can offset W-2 and business income instead of piling up unused.
For the right buyer — high income, willing to self-manage the first year, buying a property that genuinely works as an STR — it can change the after-tax math of a deal materially. For the wrong buyer it is a tail wagging a dog: a mediocre property purchased for a deduction. The deal has to pencil first. Run it through the pro forma builder before anyone talks to a CPA about depreciation.
What the loophole actually is
Under Section 469, rental losses are passive by default, and passive losses only offset passive income — useless against a salary. The exception: Treasury regulations exclude activities where the average customer stay is seven days or less from the definition of “rental activity.” A true short-term rental is treated like an operating business.
That reclassification does nothing by itself. The owner must also materially participate in the business for the losses to be non-passive. Both tests, same tax year.
Test one: the seven-day average
Take the year’s total booked nights and divide by the number of stays. At or under seven, the activity is outside the rental definition. A ski cabin averaging 3.4-night stays qualifies; a monthly corporate rental does not, and a mixed calendar can fail the average even with plenty of weekend stays.
This is measured per property, per year, from actual booking records — pull the report from the PMS, do not estimate.
Test two: material participation
Seven tests exist in the regulations; STR owners usually rely on one of three: 500+ hours in the year; 100+ hours and more than anyone else (including the cleaner and any co-host); or substantially all of the participation. The 100-hour test is the practical route for most self-managing owners — and it is exactly where audits focus.
Hours must be documented contemporaneously: guest messaging, pricing management, turnover coordination, maintenance, bookkeeping. A reconstructed spreadsheet in March does not hold up. Full-service property management in year one usually kills this test — which is why the standard play is self-manage the loss year, then hand off.
What it’s worth: the depreciation math
The engine is depreciation, accelerated by a cost segregation study and bonus depreciation — restored to 100% for qualifying property acquired after January 19, 2025. A cost seg study typically reclassifies 20–35% of the building basis (not land) into 5-, 7-, and 15-year property that can be expensed immediately.
Rough shape: $800,000 purchase, $640,000 building basis, 25% reclassified ≈ $160,000 of first-year deductions before regular depreciation. Against a 37% marginal rate, that is roughly $59,000 of federal tax deferred in year one. Deferred, not erased — depreciation recapture waits at sale, though 1031 exchanges and long holds change that conversation. The full mechanics are in our cost segregation guide.
Where it goes wrong
The property doesn’t pencil. A tax benefit on a negative-cash-flow property in a saturated market is a discount on a bad purchase. The hours log is fiction. The IRS has litigated this repeatedly and wins when documentation is thin. The average-stay math fails. One 60-day winter booking can blow the average. Regulations moved. A city that caps stays or bans STRs converts the strategy to an unlicensed hotel problem — check the regulation tracker first. Recapture surprises. Sellers who took big year-one deductions and exit in year three sometimes hand much of it back.
What to tell your client
“The loophole is real, and it is the second reason to buy this property, not the first. Here is the underwriting with zero tax benefit — it works. Here is what your CPA will model on top if you self-manage year one and your average stay stays under seven nights. Talk to the CPA before we write the offer, because the strategy affects which property we pick.”
That framing does three things: keeps the deal honest, makes the agent the one who brought the strategy up, and puts the liability where it belongs — with the tax professional.
Bottom line
A legitimate, well-trodden strategy for high-income buyers who will actually operate the property and document it. It rewards exactly the discipline good underwriting rewards — and punishes wishful thinking twice: once in cash flow, once in an audit.
This article is research, not tax or legal advice. The rules described here have thresholds, exceptions, and documentation requirements that depend on individual facts. Involve a CPA who works with short-term rentals before acting on any of it.