Cost segregation: front-load years of depreciation into year one
The short answer
A cost segregation study is an engineering analysis that splits a building into components — flooring, fixtures, cabinetry, land improvements — that depreciate over 5, 7, or 15 years instead of 27.5 or 39. Combined with 100% bonus depreciation under current law, that often converts 20–35% of a building's cost into a first-year deduction. The catch: whether you can actually use that loss depends on the passive activity rules — which is why this strategy travels with REPS or the short-term rental loophole.
Who this works for — and who it doesn't
Good fit
- Buildings (excluding land) worth roughly $400k+ where the math clears the study fee
- Investors who can use the loss: real estate professionals, STR operators, or those with passive income to offset
- High-income years where a large deduction is worth the most
Not a fit
- Small properties where the fee eats the benefit
- W-2 earners with a long-term rental and no REPS or STR angle — the loss may just sit suspended
- Owners planning a quick taxable sale — recapture claws back the win
How it works
- Run the feasibility estimate first. A reputable firm (or your CPA) projects the reclassification percentage and the tax value before you pay for the study.
- The engineering study allocates the purchase price among 5-, 7-, 15-, and 27.5/39-year property with documentation an auditor can follow.
- Bonus depreciation applies to the short-life classes — currently 100% in year one.
- Old properties can catch up: a look-back study plus Form 3115 pulls all missed depreciation into the current year — no amended returns.
- Plan the exit: recapture at sale is managed with 1031 exchanges or timing.
Want your own numbers? Run them in our cost segregation calculator — a quick estimate plus a detailed property-specific version.
A worked example
Jordan buys a $1,000,000 rental ($800,000 building, $200,000 land) and commissions a study.
Jordan's year-one depreciation
Illustrative only — reclassification percentages vary by property type, and whether the loss offsets your other income depends entirely on your passive-activity status.
Common mistakes that draw IRS attention
- DIY component allocations with no engineering support
- Taking a six-figure loss against W-2 income with no REPS or STR qualification behind it
- Forgetting land is never depreciable
- Ignoring recapture in the sale-vs-exchange decision
Frequently asked questions
How much does a cost segregation study cost?
Typical engineering-based studies run a few thousand dollars for a single-family rental up to five figures for large commercial property. The study pays for itself when the accelerated deduction meaningfully exceeds the fee — which is why we run the estimate before you commission one.
Can I do a study on a property I bought years ago?
Yes. A look-back study with a Form 3115 accounting-method change lets you catch up all the missed depreciation in the current year without amending old returns.
Will I just pay it all back when I sell?
Some of it — accelerated depreciation is subject to recapture at sale. Investors manage that with 1031 exchanges, holding periods, or by pairing the deduction with high-income years. Recapture planning belongs in the decision, not as a surprise later.
Can I actually use the loss?
That's the key question. Rental losses are passive by default and may be locked until you have passive income or sell. The loss becomes usable against W-2 or business income through real estate professional status or the short-term rental route — which is why cost segregation is a combination play, not a standalone.
Want the feasibility math before you spend a dollar?
We'll estimate the reclassification, check whether you can actually use the loss, and tell you if the study clears its own cost — before you commission anything.
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