What Is Cost Segregation, and Why Does It Matter More in 2026?
Cost segregation is an engineering-based study that breaks a rental property into its components and reassigns them to shorter depreciation schedules. Instead of writing off the whole building over 27.5 years, a study identifies the pieces that are legally personal property or land improvements, items like appliances, carpeting, cabinetry, specialty electrical, fencing, driveways, and landscaping, and moves them to 5, 7, or 15-year schedules.
That has always been legal. What changed is what happens to those reclassified components once they land on a short schedule.
The One Big Beautiful Bill, signed in July 2025, restored 100% bonus depreciation and made it permanent for qualifying property acquired after January 19, 2025. The IRS confirmed this treatment in Notice 2026-11, issued January 14, 2026. Anything a cost segregation study moves to a 5, 7, or 15-year class can now be deducted in full in year one instead of spread across those years.
For an owner who bought a St. Louis rental in the last two years, that combination is the difference between a modest annual deduction and a large first-year one.
How Cost Segregation Works on a Residential Rental Property
Residential rental buildings depreciate over 27.5 years. Commercial buildings depreciate over 39. Neither of those schedules qualifies for bonus depreciation, and the land under the building is never depreciable at all.
A cost segregation study does not change any of that. What it does is separate out the components that were never really “the building” in the first place:
- 5-year property: appliances, carpeting and removable flooring, window treatments, cabinetry and countertops that are not structural, dedicated electrical for specific equipment.
- 15-year land improvements: driveways, parking pads, sidewalks, fencing, retaining walls, landscaping, exterior lighting, site drainage.
- 27.5-year building: the structure itself, the roof, the foundation, the framing, the general plumbing and electrical systems.
On a typical residential rental, a study commonly reclassifies somewhere in the range of 15% to 30% of the building’s depreciable basis into the short-life categories. The exact share depends heavily on the property. A recently renovated property with new flooring, appliances, and site work will pull a larger share than a plain brick two-family that has not been touched in twenty years.
Can You Do a Cost Segregation Study on a Property You Already Own?
Yes, and this is the part most owners do not know. You are not limited to the year you bought the property.
If you have owned a rental for several years and never had a study done, you can have one performed now and claim the depreciation you should have taken in prior years as a single catch-up deduction in the current year. This is done by filing Form 3115, Application for Change in Accounting Method, and taking what is called a Section 481(a) adjustment. You do not amend prior returns.
The important caveat: the bonus depreciation rate that applies is the rate in effect based on when the property was acquired, not the year you run the study. A property acquired in 2022, when bonus depreciation was phasing down, does not get 100% bonus treatment just because the study happens in 2026. The catch-up is still often worth doing, but the math is different from a 2025 or 2026 purchase.
Talk to your CPA before ordering a study on an older property. The Form 3115 filing is not something to improvise.
Who Benefits From Cost Segregation, and Who Does Not
This is where a lot of online tax content oversells the strategy. A large paper deduction is only worth something if you are allowed to use it, and for most rental owners the passive activity loss rules are the gate.
The passive loss problem
Rental real estate is generally a passive activity. Passive losses can normally only offset passive income, not your W-2 salary or business income.
There is a carve-out. If you actively participate in the rental, you may deduct up to $25,000 of rental losses against other income. But that allowance phases out as income rises: it is reduced by 50 cents for every dollar of modified adjusted gross income above $100,000, and it is gone entirely at $150,000. For married filing separately, those figures are $50,000 and $75,000.
So a high-income professional who buys a St. Louis rental, runs a cost segregation study, and generates a $60,000 first-year deduction may find that almost none of it is currently deductible against their salary. It is not lost. It suspends and carries forward, and it becomes deductible against future passive income or in full when the property is sold in a fully taxable disposition. But “I will use it later” is a very different pitch than “this cuts your tax bill this April,” and the second pitch is the one cost segregation firms tend to make.
Who does get a current-year benefit
- Owners with other passive income. If you own several rentals and some are profitable, a big deduction on one can shelter income from the others.
- Owners under the income thresholds who actively participate and can use the $25,000 allowance.
- Real estate professionals. If you spend more than 750 hours during the year in real property trades or businesses in which you materially participate, and more than half of all your personal services for the year are in those businesses, your rental activity is not automatically passive. This is a demanding test with a real documentation burden, and it is a test the IRS litigates.
- Owners planning to sell other appreciated assets in the same year, where timing the deduction matters.
- Short-term rental operators who meet the material participation requirements for that specific carve-out, which works differently from the rules above.
If you are a W-2 earner above $150,000 with one rental property and no other passive income, be skeptical of anyone promising a cost segregation study will cut your tax bill this year. Ask them specifically how the deduction gets used given your situation, and get your CPA’s answer before you pay for the study.
The Recapture Tradeoff
Accelerated depreciation is a timing benefit, not a permanent one.
When you sell, the depreciation you claimed comes back. Gain attributable to depreciation on the building portion is taxed as unrecaptured Section 1250 gain, at a maximum rate of 25%, rather than at long-term capital gains rates. Depreciation claimed on the 5 and 7-year personal property that cost segregation created is subject to Section 1245 recapture, which is taxed as ordinary income up to the amount of depreciation taken.
That means a study that moved a large amount into a 5-year property and deducted it immediately can convert part of your eventual gain into ordinary income. Whether that is a good trade depends on your marginal rate now versus at sale, how long you plan to hold, and whether you intend to do a 1031 exchange or hold until death for a stepped-up basis.
Cost segregation is strongest for owners with a long hold horizon, a plan that does not involve an early sale, or a 1031 strategy. It is weakest for someone flipping in three years.
How Deca Helps St. Louis Owners Keep Better Depreciation Records
Deca Property Management does not perform cost segregation studies and does not give tax advice. What we do is maintain the records that make a study, and your CPA’s work generally, far easier and more accurate.
Every capital improvement, make-ready, and repair on a property we manage is documented with dated invoices and itemized detail through our owner portal, and our in-house maintenance division, Aced Maintenance, does most of that work directly. When a cost segregation engineer or your accountant needs to know exactly what was replaced, when, and what it cost, that record exists rather than having to be reconstructed from memory and a shoebox of receipts.
That distinction matters more than it sounds. The single most common reason an owner cannot substantiate a repair-versus-improvement position, or a component’s basis, is that nobody wrote it down at the time.
Frequently Asked Questions: Cost Segregation and Bonus Depreciation
Is bonus depreciation 100% in 2026?
Yes. The One Big Beautiful Bill, enacted in July 2025, restored 100% bonus depreciation and made it permanent for qualifying property acquired after January 19, 2025. The IRS confirmed this in Notice 2026-11. Property acquired on or before January 19, 2025 generally remains subject to the older phase-down rates that applied when it was acquired.
Is cost segregation worth it on a single rental property?
It depends far less on the property than on whether you can actually use the deduction. Rental losses are generally passive, and the $25,000 active participation allowance phases out between $100,000 and $150,000 of modified adjusted gross income. If you have no other passive income and income above that range, the deduction suspends and carries forward rather than reducing this year’s tax.
Can I do a cost segregation study on a rental I bought years ago?
Yes. You can perform a study on a property you already own and claim the missed depreciation as a catch-up deduction in the current year by filing Form 3115 and taking a Section 481(a) adjustment, without amending prior returns. The bonus depreciation percentage available depends on when the property was acquired, not when the study is performed.
What is depreciation recapture on a cost segregation study?
When you sell, depreciation claimed on the building portion is taxed as unrecaptured Section 1250 gain at up to 25%. Depreciation claimed on the 5 and 7-year personal property created by a cost segregation study is subject to Section 1245 recapture and taxed as ordinary income. Accelerated depreciation is a timing benefit, not a permanent tax savings.
Does Missouri allow bonus depreciation on rental property?
Yes. Missouri income tax begins with federal adjusted gross income and conforms to federal bonus depreciation treatment, with a historical exception only for property purchased between July 1, 2002 and July 1, 2003. Missouri owners generally do not need to maintain a separate state depreciation schedule for bonus depreciation purposes.
How much does a cost segregation study cost?
An engineering-based study on a single-family or small multifamily rental typically costs a few thousand dollars, scaling with property size and complexity. Studies generally make economic sense on properties with a depreciable basis in the low hundreds of thousands and up, and the threshold falls when bonus depreciation is at 100% because more of the benefit is realized immediately.
This article is for general informational purposes and is not tax or legal advice. Deca Property Management does not provide tax advice or perform cost segregation studies. Depreciation, passive activity, and recapture rules depend heavily on your individual circumstances. Consult a qualified CPA or tax advisor before ordering a cost segregation study or claiming any deduction described here.