Every CostSegX study follows engineering-based methodology aligned with IRS Publication 5653 (Cost Segregation Audit Techniques Guide), IRC §168 depreciation rules, and Rev. Proc. 87-56 asset class lives. Below is the source-cited walkthrough — the same standard a traditional engineering firm applies, documented for review by your CPA, your tax attorney, or an IRS examiner.
These are the IRS publications, statutes, and revenue procedures that govern cost segregation. Every component classification in a CostSegX report ties back to one of these sources. Click through to read the IRS originals.
The IRS-published methodology reference for cost segregation studies. Defines what makes a study defensible: engineering-based component analysis, supporting documentation, and CPA-filable schedules.
The statutory authority for MACRS depreciation. Defines class lives (5-yr, 7-yr, 15-yr, 27.5-yr, 39-yr) and bonus depreciation.
The IRS revenue procedure that establishes the asset class lives used in MACRS. Source authority for component-by-component classification decisions.
Governs Form 3115 filings. DCN 7 is the automatic-consent change for cost segregation look-back studies — no IRS approval required, no user fee, §481(a) catch-up taken in the year of change.
Restored 100% bonus depreciation for property both acquired AND placed in service on or after January 19, 2025. Pre-OBBBA properties remain subject to TCJA phase-down (60% in 2024, 40% in 2025 for non-OBBBA-eligible).
Five steps from address to filing-ready report. Same methodology a traditional engineering firm applies — automated where automation is sound, with explicit user confirmation at the data-collection step.
The AI agent collects property data from public records (county assessor, property cards), geospatial sources (satellite imagery, Street View), and listing data (when available). Square footage, lot size, build year, structural type, exterior features, and interior features are extracted. The user confirms or corrects any AI-extracted facts before the study runs.
The engine performs an engineering-based component analysis: each portion of the depreciable basis is classified into a recovery period (5-year personal property, 15-year land improvements, 27.5-year residential structure) per Rev. Proc. 87-56 and the IRS Cost Segregation ATG. Personal property includes items like cabinets, appliances, flooring, and fixtures. Land improvements include driveways, fencing, landscaping, and exterior lighting. The structural shell (foundation, exterior walls, roof, plumbing, electrical) remains on the 27.5-year residential schedule.
Typical residential allocation
Foundation, framing, exterior walls, roof, plumbing, electrical, HVAC.
Cabinets, appliances, flooring, fixtures, lighting, window treatments.
Driveway, fencing, landscaping, patio, walkways, exterior lighting.
Illustrative split for a typical single-family residential rental. Your actual allocation reflects your property's exact composition; ADU-only or condo properties trend toward different mixes.
Each component is valued using replacement-cost-new-less-depreciation (RCNLD) methodology. Unit prices are sourced from current-year construction-cost data (Marshall Valuation Service, the same source professional engineering firms use), adjusted for location (regional cost factors) and acquisition year (historical cost factors). Quality and condition adjustments apply where appropriate. The component values sum to the total depreciable basis.
MACRS schedules are computed for each asset class — 200% declining balance for 5-yr and 7-yr property, 150% declining balance for 15-yr property, straight-line for 27.5-yr residential structure. OBBBA bonus depreciation is applied at 100% for properties both acquired and placed in service on or after January 19, 2025. Pre-OBBBA properties follow the TCJA phase-down schedule. Year-1 deduction, multi-year schedule, and §481(a) catch-up (for look-back studies via Form 3115 DCN 7) are all calculated.
The final report includes: methodology section with IRS citations; component analysis table showing each classification and supporting reasoning; depreciation schedules in CPA-filable format; Form 3115 package for look-back studies; recapture analysis for §1245 personal property at disposition; AmeriSouth-aware cabinet classification with detachability standard documented; state conformity warnings for non-conforming states (CA, NY, NJ, others). Delivered as PDF and Excel — your CPA reviews and files using the same line items they would receive from a traditional engineering study.
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Run my free estimate →The IRS evaluates cost segregation studies on the quality of the methodology and the completeness of the documentation, not on who produced them. A defensible study requires (1) an engineering-based component analysis, (2) supporting documentation for each classification, (3) recovery-period assignments consistent with Rev. Proc. 87-56, and (4) schedules a CPA can file. CostSegX reports include all four.
Specific audit-defense features built into every report:
The result is a study consistent with IRS Publication 5653 methodology and supportable on examination through the same documentation standards a traditional engineering study produces.
CostSegX is built for residential rental properties with 1–4 units and a depreciable basis up to $1,000,000. Within that scope, the methodology produces studies aligned with the same IRS standards a traditional engineering firm applies.
Outside that scope — commercial property, 5+ unit multifamily, mixed-use, properties above $1M basis, custom or unusual construction, or properties with significant tenant improvements — on-site inspection by a credentialed cost segregation professional adds value AI cannot replicate. We refer those properties to traditional firms; email us with the property and we'll point you to the right firm.
CostSegX is a software platform. CostSegX is not a CPA firm and does not provide tax advice. The reports produced by CostSegX are intended for review and filing by your tax professional. See our Terms of Service for the full scope of platform limitations.
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