Same methodology. Same compliance. Different delivery.
Automated and traditional cost segregation studies produce the same IRS-qualified output — MACRS class-life reclassification supported by engineering documentation. They differ in who does the work (software + reviewer vs. engineer on-site), how long it takes (hours vs. weeks), and what it costs (3–20× price delta). This page separates the substantive differences from the delivery differences, and identifies when the engineered study is actually worth the premium.
Side-by-side: automated vs traditional
Software-led study
- MethodologyMACRS asset-class model + engineer review
- Construction dataRSMeans regional cost database
- DocumentationOwner-supplied plans, photos, closing docs
- Site visitNot performed
- Deliverable40–80 page report · IRS format
- Engineer on reportYes · named reviewer
- Audit supportIncluded · 3 years
Fully engineered study
- MethodologyMACRS asset-class model + engineer analysis
- Construction dataRSMeans + on-site measurements
- DocumentationPlans + invoices + engineer photographs
- Site visitYes · 4–8 hours on property
- Deliverable80–200 page report · IRS format
- Engineer on reportYes · on-site engineer
- Audit supportIncluded · life of study
The study is the same. The process is different.
✓ SAME Substantive factors
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Methodology Both use the engineering approach per IRS Cost Segregation ATG Ch. 4. MACRS asset classes assigned per Rev. Proc. 87-56.
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Construction cost source Both use RSMeans or equivalent to estimate component costs when invoices are unavailable.
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MACRS compliance Both must correctly assign 5, 7, 15, 27.5, or 39-year class lives. The IRS does not rate one path more compliant than the other.
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Report structure Both follow the 13 principal elements of a quality study: methodology, asset identification, cost allocation, documentation, etc.
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Form 3115 compatibility Both support catch-up depreciation via Change in Accounting Method if the property was placed in service in a prior year.
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Audit defensibility Neither approach, on its own, increases or decreases audit risk. Risk correlates with study quality, not price.
◎ DIFFERENT Delivery factors
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Who produces the study Automated: MACRS-trained software with named engineer review. Traditional: engineer is the primary author and performs the site analysis.
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Site visit Automated: none. Traditional: 4–8 hours on-property measuring, photographing, and interviewing owner. Adds $1,500–$4,000 to invoice.
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Turnaround Automated: 15 minutes to 24 hours. Traditional: 4 to 8 weeks from contract to report.
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Pricing model Automated: fixed-fee, tiered by property type. Traditional: custom-quoted, often tied to % of basis or a minimum hours estimate.
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Engineer access Automated: reviewer available for questions. Traditional: named engineer is typically the direct point of contact, including during audit.
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Best-fit property size Automated: <$3M basis. Traditional: >$5M basis or unusual construction. $3M–$5M is the contested middle band.
The IRS does not require a site visit.
The Cost Segregation Audit Technique Guide — the IRS's internal reference for examining cost seg studies — enumerates thirteen elements of a quality study. A site visit is not among them. The ATG explicitly contemplates studies prepared from documentation alone when documentation is adequate.
A quality study identifies and classifies a property's assets using documentation that is sufficient to support the allocations — plans, specifications, cost invoices, photographs, and other records — and is prepared by a qualified individual using a recognized methodology. The ATG does not mandate a physical inspection as a condition of study quality.— Paraphrase of IRS Cost Segregation Audit Technique Guide, Chapter 4, "Principal Elements of a Quality Study"
This is not a loophole. An engineer on-site is sometimes the most efficient way to gather documentation — but when plans, invoices, and photographs are already available, a site visit is a cost, not a quality gain.
Turnaround
From signed engagement to delivered report. The main cost of a slow study is deferred tax savings: on a $500K SFR, a 6-week delay costs ~$1,200 in time value.
Price as a % of basis
Automated providers price nearly flat — at higher basis, the % cost drops dramatically. Traditional firms scale with basis, holding the ratio roughly constant.
When the engineered study earns its price.
There are specific situations where a traditional study is the right call. They are narrower than traditional firms imply, but broader than automated providers admit. Four signals:
Complex commercial over $5M
Multi-building, mixed-use, specialized MEP (data centers, hospitals, manufacturing). 7-year personal property identification benefits materially from on-site expertise.
Unusual construction
Historic buildings, adaptive reuse, unique architectural features. Costs cannot be cleanly estimated from RSMeans alone — engineer judgment on-site adds real value.
Incomplete documentation
No construction plans, missing invoices, older property with unknown recent improvements. Site visit can reconstruct basis when records cannot.
Aggressive Year-1 deduction
A property with $2M+ in Year-1 deduction has enough IRS-examination exposure that the engineer's direct involvement in a potential audit defense pays for itself.