22 Questions in This Hub
- What is a cost segregation study?
- When is a cost segregation study worth the cost?
- How much does a cost segregation study cost?
- Can I do my own cost segregation study?
- What are the 5, 7, 15, and 27.5 year components?
- How does bonus depreciation interact with cost segregation?
- Is bonus depreciation still available in 2026?
- Does cost segregation work for a single-family rental?
- Can I do cost segregation on a property I already own?
- What if my cost seg loss is suspended by passive activity rules?
- What is depreciation recapture at sale after a cost seg study?
- Can I do cost segregation and then 1031 exchange the property?
- What property types produce the biggest cost seg benefit?
- How is cost segregation different from the de minimis safe harbor?
- Why do real estate professionals push cost seg so hard?
- What is Form 3115 and when does my CPA file it?
- How do I pick a cost segregation provider?
- Does cost segregation make sense for small multifamily under 10 units?
- Should I do the study in the year I buy or wait?
- Can I do cost seg on a property I have already fully depreciated?
- How do I track 5, 7, 15, and 27.5 year components after the study?
- What are the downsides of cost segregation?
1. What is a cost segregation study? #
A cost segregation study is an engineering analysis that breaks a rental property's depreciable basis into components with shorter recovery periods than the standard 27.5 year residential building life. Instead of depreciating the entire building over 27.5 years on a straight line, a study reclassifies portions into 5 year property (carpet, appliances, cabinets, decorative lighting), 7 year property (certain fixtures and equipment), and 15 year property (site improvements, landscaping, fencing, parking, exterior lighting). The remaining shell continues at 27.5 years.
The reclassified components depreciate faster under MACRS, and depending on the tax year they may also qualify for bonus depreciation, which lets you write off a percentage of the component cost in the first year of service. The result is significantly more depreciation in the early years of ownership, which usually produces a paper loss that offsets rental income or, for some taxpayers, other income.
2. When is a cost segregation study worth the cost? #
A study makes economic sense when the present value of the accelerated deductions clearly exceeds the study fee, your time horizon is at least 5 years, and you can actually use the resulting losses on your return. Three filters tell you if you are in the zone: building basis above roughly $500,000, marginal tax bracket above 24%, and either passive income to absorb the loss or real estate professional status that makes the loss non-passive.
Below $500,000 of basis a study can still pencil if the property has heavy 5 and 15 year content (renovated kitchens, paved parking, mature landscaping) or if you are in a year with high other income you need to shelter. Below $300,000 of basis the math usually does not work because the study fee eats too much of the benefit. The cost seg estimator gives you a first-pass benefit number before you commission the full engineering report.
3. How much does a cost segregation study cost? #
A full engineering-based study typically costs between $3,000 and $12,000 for a small to mid-size rental, with the exact number driven by property size, complexity, age, and how much renovation work has happened. Single-family rentals and small multifamily under 20 units cluster in the $3,000 to $6,000 range. Larger multifamily, mixed-use, and commercial properties run higher because the engineer spends more time on site and on the report.
Lower-cost alternatives exist (residential cost seg estimators and DIY templates that range from $400 to $1,500) but they generally do not produce the same audit-defensible documentation as a full engineering study from a qualified firm. The IRS expects a study to follow the methodology in its Audit Techniques Guide for cost segregation. Cheap reports save money up front and cost more if questioned.
4. Can I do my own cost segregation study? #
Technically yes, practically no for most landlords. Nothing in the tax code requires you to hire a third party. The IRS just requires that the methodology be defensible under its Audit Techniques Guide, which describes engineering-based, residual, sampling, rule-of-thumb, and survey methods. An engineering-based study from a qualified provider is the gold standard because it ties each reclassified dollar to a documented building component.
What you can do yourself is run an estimator to see if the benefit justifies a full study, and then commission the study only when the math is clearly there. If you self-prepare, the IRS may disallow accelerated components on audit if the methodology is undocumented. The risk-adjusted cost of a $4,000 study is almost always lower than the risk of losing accelerated deductions plus penalties. Use the DoorVault estimator for a no-commitment first pass.
5. What are the 5, 7, 15, and 27.5 year components? #
Cost seg buckets a building's basis into four MACRS recovery periods. 5 year property includes carpet, vinyl flooring, removable cabinets and counters, appliances, decorative lighting, and other personal property installed in the building. 7 year property is a smaller bucket that covers certain fixtures and equipment, often minimal in residential rentals.
15 year property is land improvements: paved parking, sidewalks, fencing, exterior lighting, mature landscaping, retaining walls, signage. This bucket is usually the second-largest reclassification on a residential study. 27.5 year property is the residential building shell that remains after the other components are pulled out: structural walls, roof, plumbing, electrical, HVAC distribution, windows, doors. A typical small multifamily study reclassifies 20% to 35% of basis into 5 and 15 year buckets, with the rest staying in the 27.5 year shell.
6. How does bonus depreciation interact with cost segregation? #
Cost seg reclassifies components into shorter lives. Bonus depreciation then lets you deduct a percentage of those reclassified components in the first year of service rather than spreading them over the 5, 7, or 15 year schedule. The two are not the same thing: cost seg gives you the components, bonus depreciation accelerates them.
The bonus rate has stepped down from 100% (2017 to 2022) to 80% in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and 0% in 2027 unless Congress restores it. A study commissioned in 2025 stacks 40% bonus on the 5, 7, and 15 year components, then the remainder depreciates on the normal MACRS schedule. The interplay is where cost seg generates its biggest year-one paper losses, and why studies on properties placed in service in earlier high-bonus years were so powerful.
7. Is bonus depreciation still available in 2026? #
Yes, but at 20% under the current statutory phase-down schedule. The bonus rate schedule under the Tax Cuts and Jobs Act has stepped down annually since 2023: 80% (2023), 60% (2024), 40% (2025), 20% (2026), and 0% (2027). Congress has discussed restoring 100% bonus retroactively, but until that becomes law you should plan around the published schedule.
For a property placed in service in 2026, a cost seg study still generates value, but the 20% bonus on reclassified 5 and 15 year components is much smaller than the 100% bonus available in 2022. The decision to commission a study now needs to factor in the lower bonus rate against the study fee and your usable losses. By 2027 the bonus is zero and cost seg returns to a pure MACRS acceleration play.
8. Does cost segregation work for a single-family rental? #
It can, but the math is tighter than on small multifamily or commercial. A single-family rental typically has less site work, smaller hardscape, and fewer 15 year components than a 4 unit building, so the percentage of basis you can reclassify is lower. A typical SFR study reclassifies 15% to 25% of basis versus 25% to 40% on small multifamily.
The break-even is usually around $300,000 to $400,000 of building basis (after subtracting land) for an engineering study to clearly pay off, and that assumes you can use the losses. Lower-cost residential estimator products fill the gap below that threshold, with the trade-off in audit defensibility noted above. Run the numbers in the cost seg estimator before committing; do not assume a rule of thumb that fits a syndicator's deal applies to your duplex.
9. Can I do cost segregation on a property I already own? #
Yes, through a lookback study. You do not need to amend prior returns. Instead you file Form 3115 (Application for Change in Accounting Method) in the current year and take a Section 481(a) catch-up deduction equal to the depreciation you would have claimed in prior years if you had used the corrected component lives from day one. The catch-up flows onto the current year's Schedule E.
Lookback studies often produce the largest single-year deductions because you are catching up multiple years of acceleration in one return. There is no statute of limitations on how far back you can go; a 10 year old property can still benefit from a study today. The trade-off is that all of the depreciation you accelerate now becomes Section 1245 ordinary-rate recapture at sale, so the lookback is most valuable when you plan to hold long-term or 1031 exchange rather than sell soon.
10. What if my cost seg loss is suspended by passive activity rules? #
This is the biggest practical mistake landlords make with cost seg. Rental losses are passive under IRC Section 469 and can only offset passive income unless you qualify for the $25,000 active participation allowance (phases out from $100,000 to $150,000 of MAGI) or qualify as a real estate professional under IRC 469(c)(7). If neither applies, your shiny new $80,000 cost seg loss suspends on Form 8582 and carries forward.
Suspended losses are not lost; they release when the property is fully disposed of in a taxable transaction. But a suspended loss is worth less than a current loss because of the time value of money, and it forces you to time the study carefully against your tax situation. Always confirm with your CPA that you can use the loss before paying for a study. If the loss will suspend, you may be better off waiting until a year when REPS or active participation applies.
11. What is depreciation recapture at sale after a cost seg study? #
Cost seg splits your recapture into two buckets at sale. The 27.5 year shell uses straight-line depreciation and recaptures under Section 1250 at a maximum 25% federal rate (the unrecaptured Section 1250 gain rate). The 5, 7, and 15 year components used accelerated methods (and often bonus) and recapture as ordinary income under Section 1245 at your marginal rate, which can be 32% to 37% for higher earners.
This is the cost most investors underestimate. A study that produced an $80,000 paper loss at a 24% marginal rate (saving $19,200 of current tax) can recapture as $80,000 of ordinary income at sale at a 32% rate (paying $25,600). The arbitrage works in your favor only when (a) you can use the deduction at a higher rate than recapture, (b) you defer recapture indefinitely through 1031 exchanges, or (c) you hold to death and step up basis. Do not commission a study without modeling recapture under your likely exit scenario.
12. Can I do cost segregation and then 1031 exchange the property? #
Yes, and it is one of the most powerful combinations available to a buy-and-hold investor. A cost seg study accelerates depreciation in the early years, generating paper losses you use against current income. When you eventually sell, a properly structured 1031 exchange defers both the capital gain and the depreciation recapture (Section 1245 and Section 1250) into the replacement property. The replacement property then continues with the relinquished property's adjusted basis, plus any new cash you put in.
You can repeat the cycle: cost seg the replacement property, accelerate again, 1031 again. This is the swap-til-you-drop strategy, and at death the heirs receive a stepped-up basis that wipes out the deferred recapture entirely. The catch is that the replacement basis is lower (because the relinquished basis carries over), so each subsequent cost seg produces a smaller acceleration benefit. Model the full chain before you start; you will hit diminishing returns after two or three exchanges.
13. What property types produce the biggest cost seg benefit? #
Properties with high concentrations of 5 and 15 year content reclassify the most. The leaders are: hospitality (hotels, short-term rentals with full furniture and finishes), restaurants and retail (decorative interiors, signage, parking, exterior lighting), small multifamily with paved lots and mature landscaping, recently renovated residential (new appliances, flooring, cabinets), and assisted living. These property types routinely reclassify 25% to 40% of basis.
Bare-land single-family rentals on small lots with minimal site work and original 1990s finishes produce the smallest benefit, often 12% to 18%. Newer construction generally outperforms older construction because more components are clearly identifiable. If you are evaluating a portfolio, prioritize studies on the highest-basis, highest-finish properties first; the per-dollar return is highest there.
14. How is cost segregation different from the de minimis safe harbor? #
Different tools that solve adjacent problems. The de minimis safe harbor under the tangible property regulations lets a landlord without an applicable financial statement expense items costing $2,500 or less per invoice or per item in the year of purchase, instead of capitalizing them. It applies to ongoing operating purchases (a $1,200 stove, a $400 toilet) and avoids the need to capitalize and depreciate every small item.
Cost segregation applies to the building's depreciable basis, typically at acquisition or after a major renovation. It reclassifies components that are already capitalized into shorter recovery periods. The two work together: use de minimis for small ongoing replacements, use cost seg to accelerate the depreciation of what is already on your basis schedule. Both are tools that small landlords routinely leave on the table.
15. Why do real estate professionals push cost seg so hard? #
Because real estate professional status (REPS) under IRC 469(c)(7) reclassifies rental losses from passive to non-passive, which means the cost seg loss can offset W-2, business income, dividends, and any other income on the return. For a high-earning REPS-qualified taxpayer, an $80,000 cost seg loss against a 37% marginal rate is worth roughly $29,600 of current tax savings.
Without REPS the same loss usually suspends on Form 8582 and you wait years to use it. The two pieces are designed to work together: REPS makes the loss usable, cost seg generates the loss. If a syndicator or marketer is selling you cost seg without first confirming you qualify (or can qualify) for REPS or have substantial passive income, they are skipping the most important question. For most W-2 investors the answer is simply that the spouse who can drop to part-time and log 750+ hours unlocks the strategy; for most others it does not.
16. What is Form 3115 and when does my CPA file it? #
Form 3115 (Application for Change in Accounting Method) is the form your CPA files when a cost seg lookback study changes how the property's basis was being depreciated in prior years. The IRS treats moving components from 27.5 year to 5, 7, or 15 year as a change in method of accounting, which requires Form 3115 along with a Section 481(a) adjustment that catches up the missed depreciation.
The catch-up adjustment is favorable (you get a deduction in the current year for under-depreciated amounts) and you do not need to amend prior returns. The form is filed with the current-year return and a duplicate copy goes to IRS Ogden. Most cost seg providers prepare the Form 3115 narrative as part of the study deliverable; your CPA assembles and files it with the 1040. Get this signed off in writing before you commit to a study so the filing path is clear.
17. How do I pick a cost segregation provider? #
Three filters narrow the field fast. First, the provider should employ engineers (often civil or structural) who do site visits, not a CPA running a residual-method spreadsheet. The IRS Audit Techniques Guide explicitly favors engineering-based studies. Second, the provider should deliver an audit-defensible report with photos, component schedules, basis allocation methodology, and a Form 3115 narrative if it is a lookback. Third, the provider should carry insurance and stand behind the report if the IRS questions component classifications.
Red flags: prices that seem too low (a $999 fixed-fee study on a $1.5M building rarely produces engineering-grade documentation), refusal to schedule a site visit on properties above $1M of basis, and aggressive 5 year reclassifications above 35% of basis without supporting detail. Get two or three quotes, and ask for sample reports redacted of client info before signing.
18. Does cost segregation make sense for small multifamily under 10 units? #
Often yes, especially if the basis exceeds roughly $400,000 to $500,000 and you have a clear plan to use the losses. Small multifamily typically has more 15 year site improvements than a single-family rental (paved driveways, multiple parking spaces, exterior staircases, larger landscaped areas) and similar 5 year content per unit. The percentage reclassified usually lands in the 25% to 35% range, which produces meaningful year-one acceleration on a property with $600,000 of building basis.
The decision still hinges on usability of the loss. If you self-manage and qualify for REPS, the case is strong. If you are a passive investor with a W-2 income above $150,000 and no other passive income, the loss likely suspends and the math weakens. Run the estimator first, then have your CPA sanity-check the usability assumption before commissioning a study.
19. Should I do the study in the year I buy or wait? #
Year of acquisition is usually the cleanest because the basis is fresh, no prior depreciation has been claimed, the engineering work captures the property as you bought it, and the resulting acceleration starts from day one of your ownership. You also avoid filing Form 3115 because you are not changing methods, just choosing the correct method at the start.
Lookback studies on properties owned for several years are still valuable (often producing larger one-year deductions because of the catch-up adjustment) but the basis has typically been partially depreciated already, the engineering may need to reconstruct earlier conditions, and the recapture exposure at sale is concentrated. If you are buying this year and the basis clears the threshold, schedule the study during the closing year so it lands on the first return.
20. Can I do cost seg on a property I have already fully depreciated? #
No. Cost seg reclassifies components that still have remaining basis to depreciate. If the building shell is fully depreciated (which takes 27.5 years of straight-line ownership without any major renovations adding new basis), there is no remaining basis to reclassify. The components would have already been written off under the original 27.5 year schedule.
What you can do on a long-held property is conduct a lookback study while there is still meaningful undepreciated basis remaining (typically before year 20), or commission a study after a major renovation that added significant new capitalized basis. Renovations that add a new roof, HVAC, kitchens, or site work create fresh capitalizable basis that a study can break into shorter-life components.
21. How do I track 5, 7, 15, and 27.5 year components after the study? #
Most CPAs add separate fixed-asset records for each reclassified component on the property's depreciation schedule, typically inside the tax software's asset register. The accounting side is harder for a small landlord without dedicated software because each component now has its own placed-in-service date, basis, recovery period, and accumulated depreciation. By year three the schedules become unwieldy in a spreadsheet.
DoorVault tracks each component as a tagged sub-asset under the parent property, automatically computes annual depreciation per component, and rolls up totals for Schedule E. When you sell, the recapture math is precomputed: Section 1245 ordinary on the 5, 7, and 15 year components and Section 1250 capped at 25% on the 27.5 year shell. This is one of the few places where the spreadsheet-to-software transition pays for itself in a single tax year.
22. What are the downsides of cost segregation? #
Five things to weigh before committing. First, study fees are real and non-refundable whether or not you can use the loss. Second, accelerated depreciation creates Section 1245 recapture taxed at ordinary rates at sale, often higher than the 25% Section 1250 rate that would have applied. Third, suspended passive losses sit on Form 8582 if you cannot use them currently, costing you the time value of money. Fourth, the schedules become more complex and your CPA fee may increase in subsequent years.
Fifth, audit risk increases marginally because cost seg is on the IRS radar, especially aggressive reclassifications. None of these are showstoppers when the math works. They are reasons to model the full lifetime tax picture (current deduction value minus recapture cost minus study fees, present-valued) rather than focusing only on the headline year-one deduction the marketing materials lead with.