Cost Segregation and the 1031 Exchange

What Cost Segregation Does

When you buy real property, the IRS assigns a single depreciation life to the entire improvement value: 27.5 years for residential rental (apartments, multifamily), 39 years for commercial (office, retail, industrial). That schedule is conservative and slow by design — Congress intended it to understate economic reality.

Cost segregation is an engineering-based tax study that breaks apart the improvement value into its component parts and reclassifies those components into their correct depreciable lives under the MACRS system. What a single-figure $3M apartment building becomes after a cost seg study:

The short-life components (5, 7, and 15-year property) were already eligible for accelerated depreciation under prior law. What changed in 2025 is that OBBBA made them eligible for 100% immediate expensing permanently.

What OBBBA Changed in 2025

The Tax Cuts and Jobs Act of 2017 created 100% bonus depreciation but wrote in a phasedown schedule: 100% through 2022, then 80% in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and zero in 2027. Without a legislative fix, the bonus depreciation benefit would have been largely gone by 2026.

The One Big Beautiful Bill Act (OBBBA, signed July 2025) permanently eliminated the phasedown and restored 100% bonus depreciation for qualified property acquired and placed in service after January 19, 2025.¹ There is no new sunset date. Every dollar of 5-year, 7-year, and 15-year property placed in service from that date forward can be deducted in full in the year it is placed in service.

The acquisition date matters: property for which a binding written contract existed before January 20, 2025 is treated as acquired on the contract date and may not qualify. Property acquired and placed in service on or after January 20, 2025 qualifies fully, including replacement properties in exchanges that closed in 2025 and 2026.¹

How Cost Segregation Interacts With 1031 Exchange Carryover Basis

This is where 1031 exchange and cost segregation planning intersects most precisely — and where the details matter.

When you complete a 1031 exchange, the replacement property's tax basis is not its full purchase price. Under IRC § 1031(d), the adjusted basis of the replacement property equals the adjusted basis of the relinquished property (plus any additional cash paid, minus any boot received). This is the carryover basis. The remaining portion of the replacement property's value — everything above the carryover basis — is excess basis that comes from new money invested.²

For depreciation purposes, the IRS requires a "bifurcated basis" approach on 1031 exchange property:

• The exchange basis continues the old property's depreciation schedule — same remaining life, same method as the relinquished property. If your old property had 14 years remaining on its 27.5-year schedule, the exchange basis portion of the replacement property depreciates over those same 14 years.
• The excess basis starts fresh — a new 27.5-year (or 39-year for commercial) depreciation schedule beginning in the year the replacement property is placed in service.

Cost segregation applies to the improvement value of the replacement property across both basis layers. A cost seg study identifies which components of the building can be reclassified as 5-year, 7-year, or 15-year property. For the exchange basis layer, reclassified components continue on the old property's remaining schedule (accelerated from 27.5 years to 5 or 7 years, which is still faster). For the excess basis layer, reclassified components get fresh short-life schedules — and under OBBBA, are fully deductible in year one via bonus depreciation.

Practically, the largest cost seg benefit comes from the excess basis — the new money you invested above the old carryover basis. If you sold a property with a $600,000 adjusted basis and bought a $3,000,000 replacement, approximately $2,400,000 is excess basis that gets fresh depreciation. Cost seg can reclassify 10–20% of that as short-life property — $240,000–$480,000 eligible for 100% first-year deduction under OBBBA.

The §1250 Recapture Chain: Faster Depreciation Creates Future Tax Liability

Cost segregation accelerates deductions now. The tradeoff is that every dollar of accelerated depreciation on real property creates an equal dollar of §1250 unrecaptured gain when you eventually sell.³ That recapture is taxed at a maximum federal rate of 25% — a rate that does not disappear when you do another 1031 exchange. It follows the carryover basis into each successive replacement property.

The three paths for accumulated §1250 recapture:

1. Taxable sale: Recapture is recognized and taxed at up to 25% federal, plus state, plus 3.8% NIIT if income exceeds thresholds. On $400,000 of accumulated recapture, that is roughly $100,000–$120,000 in combined federal and net investment income tax.
2. Another 1031 exchange: Recapture is deferred again. It carries forward into the next replacement property's carryover basis, growing with each new round of accelerated depreciation. The liability defers indefinitely as long as exchanges continue.
3. Death and step-up: The § 1014 step-up at death erases all deferred gain — including every dollar of accumulated § 1250 recapture — by resetting the heir's basis to fair market value. The deferred tax disappears permanently. This is the primary exit strategy for investors who intend to hold real estate for life.

Passive Activity Loss Limitation: Who Actually Captures the Year-1 Deduction

Cost segregation creates large paper losses — but whether those losses immediately reduce your tax bill depends on your classification under the passive activity rules of IRC § 469.

Passive Investors (Most Rental Property Owners)

If you own rental property as a passive investor — a high-income W-2 employee or business owner who does not qualify for real estate professional status — the losses generated by cost segregation are passive losses. They can offset passive income (other rental income, limited partnership distributions, publicly traded partnership income), but they cannot offset wages, business income, or portfolio income such as dividends and interest.

Large cost seg losses in excess of passive income are suspended as passive activity loss carryforwards under the same rules discussed in the passive activity losses guide. They do not reduce your current tax bill unless you have passive income to absorb them. They carry forward and are eventually released on a fully taxable sale, or they die unused at death.

Real Estate Professional Status (REPS): The Key That Unlocks Full Benefit

Under IRC § 469(c)(7), a taxpayer qualifies as a real estate professional if:

• More than 50% of total personal service hours during the year are spent in real property trades or businesses in which the taxpayer materially participates, and
• The taxpayer spends more than 750 hours per year in those real property activities.⁴

A REPS investor who also materially participates in the specific rental activity can treat rental losses as non-passive. This converts cost seg deductions into deductions against any income — wages, business income, dividends. A $400,000 cost seg deduction for a REPS investor in the 37% marginal bracket produces $148,000 in federal tax savings in year one.

The REPS test applies separately each year. An investor who retired from W-2 income, whose spouse manages properties full-time, or who has shifted to full-time real estate investment may qualify. The 750-hour threshold and the majority-of-working-time test require careful documentation throughout the year.

Worked Example: $3.2M Replacement Apartment Complex

Marcus sold a $2.4M fourplex in January 2026 and completed a 1031 exchange into a $3.2M apartment complex in March 2026. His old adjusted basis (carryover basis) was $440,000. He invested $600,000 in new equity; the rest was debt replacement.

Cost Segregation Study Results

Marcus commissions a cost segregation study ($14,000 fee). The study identifies 12% of the improvement value as short-life property:

Under OBBBA 100% bonus depreciation (property placed in service March 2026, after January 19, 2025):¹ the $345,600 in short-life components is deductible in full in the 2026 tax year.

Scenario A: Marcus Qualifies as a Real Estate Professional

Marcus retired from his corporate career in 2025 and now manages his 12-unit portfolio full-time. He meets the REPS test for 2026. The $345,600 cost seg deduction offsets his ordinary income at the 37% federal rate:

Even accounting for the deferred recapture liability, Marcus nets approximately $27,000 in permanent tax savings on a present-value basis — and has use of the $127,872 tax payment he did not make in 2026 invested elsewhere for the hold period. If he holds until death, the step-up eliminates the $86,400 recapture liability entirely.

Scenario B: Marcus Is a Passive Investor

If Marcus still has W-2 income and does not qualify as a real estate professional, the $345,600 deduction creates $345,600 in passive losses. These losses suspend under § 469 and carry forward. He can absorb them against:

• Passive income from the apartment complex itself (net operating income above debt service)
• Passive income from other rental properties or limited partnerships
• All income in the year of a fully taxable sale

The cost seg study still makes sense if Marcus expects passive income to absorb the losses within 5–7 years, or if he plans a taxable sale in the medium term. It is less compelling if the losses are likely to suspend for a decade and eventually die unused at death.

When to Commission a Cost Segregation Study

A cost seg study has a setup cost ($5,000–$18,000 for most commercial and multifamily properties) that must be compared against the tax benefit it generates. The math usually works when:

• Property value exceeds $1M: Below $1M, the reclassifiable components are often not large enough to justify study costs, especially for residential properties. For commercial properties, some providers offer engineered studies starting at $5,000 for properties in the $1M–$2M range.
• Replacement property has a large excess basis: The cost seg benefit is largest on the new-money portion of the purchase above the carryover basis. An investor who paid $3M for a replacement property against a $400K carryover basis has $2.6M in excess basis — a large base for cost seg to work on.
• The investor qualifies (or nearly qualifies) for REPS: The full benefit of cost segregation is unlocked only with REPS. If REPS status is obtainable, the year-1 tax savings are typically 5–10× the cost of the study.
• Hold period is 10+ years: The deferred recapture liability grows with the hold period — but so does the compounding benefit of investing money that would otherwise have gone to taxes. Longer holds and estate-planning exits (step-up at death) improve the cost-benefit.
• The investor has other passive income to absorb losses: Even without REPS, passive investors with income from other real estate holdings, limited partnerships, or other passive sources can use cost seg losses immediately against that income.

Timing: When to Order the Study

Commission the cost seg study within the first few months after the replacement property closes. The study must be completed before the tax return for the year the property is placed in service is filed (or amended). A study completed and delivered before the April tax deadline can be applied to that year's return, or you can file an extension and use the September or October deadline. Properties placed in service in prior years can still be studied — the IRS allows a catch-up deduction via a § 481(a) adjustment on Form 3115 (Change of Accounting Method) without amending prior returns.

Cost Segregation and the DST: A Limitation to Know

If your replacement property is a Delaware Statutory Trust (DST), you cannot commission a cost segregation study on your interest in the trust. The DST sponsor controls the property, and the Seven Deadly Sins restrictions prohibit new capital expenditures after closing. DST investors receive their pro-rata share of the DST's depreciation schedule — typically straight-line 27.5 or 39 years at the trust level. No cost seg benefit passes through to individual investors.

This is one of the financial planning trade-offs between direct replacement property (where cost seg is available) and a DST (passive, no management burden, but no cost seg). For an investor who qualifies for REPS and has a large basis gap, the cost seg opportunity on direct property can be worth hundreds of thousands of dollars — an advantage DSTs cannot match.

How the Financial Advisor Fits into Cost Segregation Planning

The cost seg study is typically ordered by the property owner and performed by a cost segregation engineering firm. The CPA incorporates the results into the tax return. But the decision of whether to commission the study, what to do with the resulting deductions, and how cost seg interacts with the overall financial plan is where a fee-only financial advisor adds the most value.

Specifically, a financial advisor can model:

• Whether pursuing REPS is financially worthwhile given the investor's other income and working arrangements
• The present-value comparison between taking the immediate deduction (with future recapture) versus spreading depreciation over the standard schedule
• How suspended PAL carryforwards interact with new cost seg losses and whether strategic boot in the exchange might be preferable to accelerating passive losses
• The estate planning integration — whether the step-up-at-death exit strategy justifies aggressive cost seg now, given the investor's age and estate planning goals
• How cost seg interacts with the decision to exchange again versus sell taxably in the next property transaction

DST commission conflicts aside, the cost seg decision is one of the clearest examples of where the 1031 exchange and the broader financial plan need to be modeled together rather than in parallel silos.

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