Real Estate Tax Calc
Why shorter-life classes matter
A standard rental building uses 27.5- or 39-year straight-line depreciation. Components reclassified into 5-, 7-, or 15-year MACRS classes depreciate faster — and may qualify for bonus depreciation in year one. A cost segregation study has a qualified engineer identify and support each reclassification.
What falls into each class
5-year property in residential rentals typically includes carpeting, appliances, and certain electrical or plumbing components that directly serve the tenants. 7-year property includes office furniture and some fixtures. 15-year property (land improvements) covers exterior items: parking lots, sidewalks, landscaping, fences, and outdoor lighting — particularly impactful for commercial and larger residential complexes.
How much can typically be reclassified
Cost seg studies on residential rentals typically reclassify 10–30% of the total building cost into shorter-life classes; commercial buildings often see a higher percentage due to more extensive equipment and improvements. The exact amount depends on the property's construction and components. Use the cost segregation calculator for a first-pass estimate.
The MACRS mechanics of each class
The shorter classes use 200% declining balance (5- and 7-year property) or 150% declining balance (15-year property), switching to straight-line when advantageous, versus the plodding straight-line method on the 27.5-/39-year building. Even without bonus depreciation, that front-loads deductions substantially — a 5-year asset under the half-year convention writes off 20% in year one, 32% in year two, and 19.2% in year three. Land improvements (15-year) fall under the General Depreciation System using 150% declining balance. The point of a study is not just to find these assets but to defensibly value and document them so the reclassification survives an audit.
A worked example
Take a $1,000,000 residential rental with $200,000 allocated to land, leaving an $800,000 depreciable building. Straight-line over 27.5 years gives about $29,090 of depreciation per year. Now run a cost seg study that reclassifies 25% of the building — $200,000 — into 5-, 7-, and 15-year property, leaving $600,000 in the 27.5-year class. With 100% bonus depreciation available on the short-life property, you could deduct roughly $200,000 in year one from the reclassified assets, plus about $21,800 on the remaining building — a first-year deduction near $222,000 instead of $29,090. At a 32% marginal rate that's roughly $71,000 of tax deferred into year one.
Bonus depreciation is what supercharges it
The reason 5-, 7-, and 15-year classifications matter so much is that they're eligible for bonus depreciation, which lets you expense a large percentage of the asset immediately rather than spreading it over its class life. Bonus depreciation has been a moving target: it was 100% through 2022, then phased down (80% in 2023, 60% in 2024, 40% in 2025) under the 2017 law, before 2025 legislation restored 100% bonus depreciation for qualifying property acquired and placed in service after January 19, 2025. Because the rate depends on the placed-in-service date and current law, confirm the year's percentage before you model — the difference between 40% and 100% bonus is enormous on a large reclassification.
The recapture trade-off at sale
Accelerating depreciation isn't free money — it's a timing benefit with a cost at sale. The building portion (Section 1250) recaptures at a maximum 25% rate, but the 5-, 7-, and 15-year components are Section 1245 property, and their depreciation recaptures at ordinary income rates, which can exceed 25%. So a cost seg study converts some future gain from the capped 1250 rate into higher-rate 1245 recapture. That's usually still worth it because of the time value of the earlier deductions — and because a later 1031 exchange or a step-up at death can defer or eliminate the recapture entirely — but it must be modeled, not assumed.
Who benefits most, and the passive-loss catch
Cost segregation shines for taxpayers who can actually use the accelerated loss. For most rental owners, the deductions are passive and can only offset passive income unless you qualify as a real estate professional or run a short-term rental with material participation (the STR loophole). Otherwise the excess loss suspends and carries forward until you have passive income or sell the property. High earners with real estate professional status, or STR operators, get the biggest immediate cash-flow benefit. A quick pre-study estimate and a conversation with your CPA about passive-loss limits should come before you pay for a full engineering study.
Do it right: quality of the study
The IRS Cost Segregation Audit Techniques Guide favors engineering-based studies that inspect the property and price components from actual construction records, over rule-of-thumb allocations. A shoddy study — or a DIY spreadsheet with unsupported percentages — is the kind of aggressive position that draws scrutiny and can be unwound on audit. Expect a reputable study to cost a few thousand to tens of thousands of dollars depending on property size, and to pay for itself many times over on a property with meaningful basis. For an existing property you've owned for years, a study can still be done and the missed depreciation caught up in one year via a Form 3115 change of accounting method.
Qualified improvement property: the other short-life bucket
Beyond the 5-, 7-, and 15-year classes, interior improvements to nonresidential buildings can qualify as Qualified Improvement Property (QIP) — a 15-year class (after the 2020 CARES Act "retail glitch" fix) that's also bonus-eligible. QIP covers interior renovations made after the building was placed in service, excluding enlargements, elevators/escalators, and internal structural framework. For an investor renovating a commercial space or the common areas of a mixed-use building, QIP is a major accelerator that a cost seg study will identify alongside the personal-property components. Residential rentals don't use QIP, but their interior fixtures still land in the 5-year class.
Watch the mid-quarter convention
Most depreciation uses the half-year convention, treating assets as placed in service mid-year. But if more than 40% of your total personal property (the 5- and 7-year assets) for the year is placed in service in the fourth quarter, the mid-quarter convention kicks in, reducing first-year depreciation on those assets. Because a cost segregation study on a property bought late in the year can dump a large amount of 5-/7-year property into Q4, this trap is easy to trigger. With 100% bonus depreciation the effect is muted (bonus isn't subject to the convention), but if bonus is partial or you elect out, the mid-quarter rule can meaningfully cut your first-year deduction — a reason to model the timing.
Interaction with a future 1031 exchange
Cost segregation and 1031 exchanges can work together but need coordination. The accelerated 1245 (personal property) depreciation you take now recaptures at ordinary rates, and after the 2017 law personal property no longer qualifies for like-kind treatment — so on an exchange, the 1245 portion may be recognized rather than fully deferred, while the 1250 building portion carries forward. Many long-term investors accept this because a later step-up at death erases all the recapture anyway. If you plan to exchange, tell your CPA before the study so they can weigh how much 1245 recapture you might trigger versus the value of the earlier deductions.
Timing and who should consider it
The best time to order a study is the year you acquire or complete construction, so the accelerated deductions land when you can use them — but a look-back study with a Form 3115 catch-up works for older properties too. Cost segregation makes the most sense when: the building basis is large (often cited as $500,000+, though smaller STRs can pencil out), you'll hold long enough to justify the recapture trade-off, and you can actually use the losses (real estate professional status, a materially-participated STR, or ample passive income). If you expect to sell soon at a gain and can't defer, the recapture may claw back much of the benefit — run the numbers first with the cost segregation calculator and your CPA.
Repairs, partial dispositions, and the hidden bonus
A quality study pays off beyond year one. Because it itemizes building components, it enables partial disposition deductions: when you later replace a roof, HVAC unit, or parking lot, you can write off the remaining basis of the old component instead of depreciating two versions at once — and you avoid recapture on the retired asset. The component detail also sharpens the repair-versus-capitalize analysis under the tangible property regulations, since you can measure a repair against the specific unit of property rather than the whole building. These downstream benefits are easy to overlook when weighing a study's cost, but over a long hold they can add up to as much value as the original acceleration.
Frequently asked questions
What is 15-year property in a cost seg study?
Land improvements like parking lots, sidewalks, fences, and landscaping — depreciated over 15 years and potentially eligible for bonus depreciation.
How much of a building can be reclassified?
Typically 10–30% for residential rentals, more for commercial — it depends on the property's components.
Does cost segregation increase my taxes when I sell?
It shifts some gain into Section 1245 recapture, taxed at ordinary rates rather than the 25% cap on real property. The earlier deductions usually outweigh this, and a 1031 exchange or step-up at death can defer or erase the recapture.
Can I do a cost seg study on a property I've owned for years?
Yes. You can catch up the missed accelerated depreciation in one year using a Form 3115 change of accounting method, without amending prior returns.
Do I need to be a real estate professional to benefit?
Not to do the study, but to use the losses against non-passive income you generally need real estate professional status or a materially-participated short-term rental. Otherwise the losses are passive and carry forward.
What is the difference between 5-, 7-, and 15-year property?
5-year property is tenant-serving items like carpet and appliances; 7-year property is office furniture and certain fixtures; 15-year property is land improvements like parking lots, sidewalks, fences, and landscaping. All three depreciate far faster than the 27.5- or 39-year building.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.