Standard depreciation spreads a residential building's cost over 27.5 years — useful, but slow. Cost segregation is the engineering-based process of identifying everything inside and around that building that the tax code lets you depreciate far faster. It is the difference between deducting $14,000 a year and $140,000 in year one.
Here is a practical look at how studies work, the interaction with bonus depreciation, and the honest math on when a study pays.
What a Cost Segregation Study Actually Does
An engineering-based study inspects your property (physically or virtually) and reallocates its cost basis from 27.5/39-year 'building' into faster buckets:
- 5-year property — appliances, carpet, furniture, decorative fixtures, window treatments
- 7-year property — certain equipment and furnishings
- 15-year property — land improvements: driveways, fencing, landscaping, pools, patios
- Remaining basis stays as 27.5- or 39-year building structure
Bonus Depreciation: The Multiplier
Property in the 5, 7, and 15-year classes may qualify for bonus depreciation. Current federal law restored 100% additional first-year depreciation for qualifying property acquired after January 19, 2025, subject to acquisition, placed-in-service, related-party, business-use, and other eligibility rules. Transition rules can differ for property acquired under an earlier binding contract, so acquisition and placed-in-service dates belong in the plan.
Even when bonus depreciation is unavailable or an election out is preferable, moving eligible components to 5-, 7-, and 15-year schedules can accelerate deductions compared with building depreciation.
The Math: When a Study Is Worth It
Studies on single residential properties typically cost $2,500–$7,500; large commercial studies more. The value depends on your depreciable basis and — critically — whether you can use the losses:
- Depreciable basis above ~$200,000 usually clears the cost-benefit bar
- STR owners using the short-term rental loophole get W-2 offset value — the highest-value use case
- Investors with real estate professional status can absorb unlimited losses
- Purely passive investors may only bank suspended losses — still valuable at sale, but discounted
Already Owned the Property for Years? Catch Up Without Amending
A look-back study plus Form 3115 (change in accounting method) lets you claim every dollar of missed accelerated depreciation as a one-time 'Section 481(a) adjustment' on the current return — no amended returns required. We have seen catch-up deductions in the hundreds of thousands for long-held portfolios.
Recapture: Plan the Exit Before You Accelerate
Accelerated depreciation is a deferral-plus-arbitrage strategy, not free money. At sale, 1245 components and building depreciation face recapture — though often at rates below the ordinary rates you offset, and a 1031 exchange defers recapture entirely. Good planning models the full lifecycle: acquisition, hold, and exit.
Before commissioning a study, have your advisor run the numbers — our real estate tax practice provides no-cost benefit estimates so you decide with projections, not promises.
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Explore the serviceFrequently Asked Questions
Is cost segregation legal?
Completely. The methodology comes from decades of case law and the IRS's own Cost Segregation Audit Techniques Guide. What matters is using a quality engineering-based study with documentation — not a spreadsheet guess.
Can I do cost segregation on a property I bought years ago?
Yes. A look-back study with Form 3115 claims all missed accelerated depreciation in the current year as a Section 481(a) adjustment — one of the best 'found money' opportunities for longtime landlords.
Does cost segregation work for short-term rentals?
STRs are the best use case: furniture-heavy properties reclassify 25–35% of basis on average, and hosts who materially participate can use the losses against W-2 and business income under the STR exception.
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About the author
Samera Harvey, EA — Enrolled Agent & Founder
Samera Harvey is an IRS Enrolled Agent and the founder of Simply Smart Tax Advisors. She began her career in public accounting serving high-net-worth families, multi-state entities, and corporate tax structures — then built her own real estate investment companies, renovated and resold hundreds of properties, and educated more than 2,000 aspiring investors. She founded Simply Smart Tax Advisors to help entrepreneurs build tax strategy alongside wealth, not after it.
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