Real Estate Tax Calc
The basic ROI calculation
Cost segregation ROI compares the net present value of accelerated tax savings against the cost of the study. The rough estimate: multiply the reclassifiable portion of the depreciable basis (often 20–35% for residential, 25–40% for commercial) by the bonus depreciation percentage and your effective marginal tax rate to get the approximate first-year tax savings. Then subtract the study fee to see the net gain in year one.
Example: $800,000 depreciable basis, 30% reclassification = $240,000 in accelerated assets. Apply 40% bonus (2025 rate): $96,000 first-year deduction. At a 32% marginal rate: $30,720 tax savings in year one. If the study cost $8,000, ROI is ($30,720 − $8,000) ÷ $8,000 = 284%. Even on a conservative basis this often pays.
The time-value factor
The full ROI story includes what you do with the money saved. A $30,000 check you don't write to the IRS this year — and can invest in the next property — compounds forward. Even if recapture eventually brings some of it back, you had years of use of that capital. The larger the property and the higher your marginal tax rate, the more powerful the time-value argument becomes.
When ROI is negative
Studies rarely pay on lower-value properties. A study that costs $5,000 on a $100,000 building (only $90,000 depreciable) might reclassify $25,000 at 40% bonus and 24% tax rate = $2,400 in savings — a loss before factoring in paperwork. Rule of thumb: consider studies on properties with at least $500,000 of building value, and use the cost segregation calculator to estimate your specific savings before engaging an engineer.
Current bonus rate: 100% again after the OBBBA
The single biggest input to ROI is the bonus depreciation rate, and it changed dramatically in 2025. The One Big Beautiful Bill Act, signed in July 2025, restored 100% bonus depreciation permanently for qualified property acquired and placed in service after January 19, 2025 — reversing the scheduled phase-down (80% in 2023, 60% in 2024, 40% in 2025) that had been shrinking cost-seg benefits. At 100%, every dollar of reclassified 5-, 7-, and 15-year property is deductible in year one, which roughly doubles the first-year deduction compared with the 40% rate the older examples above assume. That makes the ROI case stronger than it has been in years. If your property was placed in service before the January 19, 2025 cutoff, though, the lower phase-down rate for that year still governs, so always match the bonus rate to the actual placed-in-service date.
Look-back studies: capturing missed depreciation with Form 3115
You do not have to run a cost segregation study in the year you buy. On a property you have owned for several years, an engineer can perform a look-back study and you claim the entire cumulative difference between the depreciation you took and what you could have taken as a single Section 481(a) adjustment — filed with Form 3115 (Application for Change in Accounting Method) in the current year, with no need to amend prior returns. This can drop a very large one-time deduction onto a single year's return, which is often the highest-ROI move available to a long-time owner. Because bonus depreciation is now 100% again, a look-back on a property bought in 2025 or later can pull forward substantial deductions at once. The trade-off is a somewhat higher study cost and the modest complexity of the Form 3115 filing.
ROI only counts if you can use the deductions
A study that generates a $150,000 first-year deduction is worthless this year if you cannot deduct it against income. Rental losses are generally passive, deductible only against passive income unless you qualify under an exception: the $25,000 active-participation allowance (phasing out between $100,000 and $150,000 of modified AGI), real estate professional status combined with material participation, or the short-term rental position where average guest stays are seven days or less and you materially participate. If none applies, the deduction is suspended and carries forward — you still get it eventually, but the ROI is a deferral, not an immediate win. Run the passive-loss analysis before you pay for a study, because the time value of a deduction you cannot use for years is far lower than the headline number suggests.
Recapture and the true, after-tax ROI
Cost segregation accelerates deductions; it does not create new ones. The depreciation you front-load reduces your basis, so more gain is exposed when you sell. Reclassified 5- and 7-year components are Section 1245 property recaptured at ordinary rates up to the depreciation taken, and the building portion carries unrecaptured Section 1250 gain taxed at up to 25%. The genuine ROI, then, is the time value of paying tax later rather than sooner — often years of use of the deferred cash, which you can reinvest into the next property — plus any permanent rate arbitrage if your marginal rate is lower at sale or you exit through a 1031 exchange or a step-up in basis at death. A defensible ROI estimate discounts the future recapture back to present value rather than ignoring it.
Choosing a provider and documenting the study
Not all studies are equal. A defensible study is an engineering-based analysis that inspects the property, reviews construction records or a purchase-price allocation, and cites the case law and IRS guidance (the Cost Segregation Audit Techniques Guide) supporting each classification. Fees generally run from a few thousand dollars for a small residential property to tens of thousands for a large commercial building. Beware 'rule of thumb' or software-only studies with no site work — they are cheaper but far weaker if the IRS examines the return. Keep the full report, the engineer's schedules, and the underlying invoices with your permanent records. A study that saves $30,000 but cannot survive an exam is a false economy; the incremental cost of a quality provider is usually small relative to the deduction at stake.
A decision framework before you commission a study
Rather than react to a provider's marketing, work through five questions in order. One: is the building basis large enough? Below roughly $500,000 of depreciable value the fee often eats the savings. Two: what bonus rate applies? At today's 100% rate the case is strong; at a phased-down rate on an older placed-in-service date it is weaker. Three: can you use the loss this year? If it will be suspended by the passive-activity rules, the ROI is a deferral, not an immediate return, and should be discounted accordingly. Four: how long will you hold? The longer the hold before sale, the more valuable the deferral, because you enjoy years of use of the deferred cash before any recapture. Five: how will you exit? A 1031 exchange or a step-up in basis at death can turn the deferral into permanent savings, sharply raising the true ROI; a straight taxable sale in a year or two does the opposite.
Run the numbers through the cost segregation calculator with your actual basis, marginal rate, and expected hold period before signing an engagement. A quick screen: if the estimated first-year tax savings are at least three to five times the study fee and you can use the loss, the study almost always pays. If the savings barely exceed the fee, or the loss will sit suspended for years, the money is often better spent elsewhere.
Frequently asked questions
How do I calculate cost segregation ROI?
Estimate first-year tax savings (reclassified basis × bonus rate × marginal rate), subtract the study fee, and divide by the fee. At meaningful property values and marginal rates above 24%, ROI is often 3–10x the study cost in year one alone.
What property size justifies a cost segregation study?
As a general rule, properties with $500,000 or more in depreciable building value are typically worth the study. Below that, the savings often don't exceed the cost.
Does the bonus depreciation phase-down affect ROI?
Yes. As bonus rates step down (40% in 2025, 20% in 2026), first-year savings shrink. Timing a purchase and study for a higher bonus year improves ROI meaningfully.
Isn't bonus depreciation back to 100% now?
Yes, for property placed in service after January 19, 2025. The OBBBA restored 100% bonus permanently, so the phase-down described above no longer applies to newly placed-in-service assets — which materially improves cost-seg ROI. Property placed in service before that date still uses the lower rate for its year.
Can I do a cost segregation study on a property I have owned for years?
Yes. A look-back study lets you claim the cumulative missed acceleration as a Section 481(a) catch-up adjustment via Form 3115 in the current year, without amending prior returns. For long-time owners this is often the highest-ROI option.
Does cost segregation actually save tax or just delay it?
Primarily it delays it — you accelerate deductions and later face more recapture at sale. The real return is the time value of deferring tax (cash you can reinvest for years) plus any permanent savings from a lower future rate, a 1031 exchange, or a step-up in basis at death.
How long should I plan to hold a property for a study to pay off?
The longer the hold, the better the ROI, because you keep the use of the deferred tax for more years before recapture. A very short hold can backfire — you accelerate deductions and then face recapture almost immediately, capturing little time-value benefit. If you may sell within a year or two, run the after-tax, present-value math carefully before paying for a study.
Does a higher marginal tax rate improve the ROI of a study?
Yes. First-year savings equal the accelerated deduction times your marginal rate, so a taxpayer at 37% captures far more up-front value than one at 22%. High-income investors who can also use the loss under the passive-activity rules see the strongest returns. If your rate is low or the loss will be suspended, the ROI shrinks accordingly.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.