Sources
Sources & Citations
Every IRS publication, Treasury regulation, court case, engineering standard, and data source we use — with direct links and what each is for.
Cost segregation is a tax strategy with a deep, well-documented authority base. Below is the full list of primary sources our content and engine are checked against. Every claim on this site links back to one of these — search this page for any source you want to verify against.
IRS publications
Primary source for asset-class lives, MACRS recovery periods, and bonus depreciation rules. Cited on every page that mentions MACRS, asset class life, or 5/7/15/27.5/39-year property.
Examination criteria for cost segregation studies. Our methodology is explicitly aligned with this guide. Cited anywhere we describe what makes a study 'IRS-defensible.'
The form used to claim missed depreciation under §481(a). Cited on every lookback / catch-up depreciation page.
The form used to report depreciation claimed in the tax year. Cited on pages explaining how cost-seg results land on a return.
Authoritative source on rental-property depreciation and passive activity rules.
Authoritative source on §469 passive activity loss limitations and the real estate professional exception.
Treasury regulations & US Code
Foundational regulation defining how property is depreciated under MACRS.
General Asset Account (GAA) rules and partial-disposition elections.
The class-life table that drives 5-year, 7-year, and 15-year property classifications. Foundational for any cost-seg engineering analysis.
The statute behind bonus depreciation. Pre-OBBBA phase-down was 80% (2023), 60% (2024), 40% (2025). OBBBA permanently restored 100% for 2025+.
The passive activity loss rules. §469(c)(7) is the real estate professional exception. §469(i) is the $25,000 active-participation allowance for non-REPS investors.
Average customer use 7 days or less takes the activity out of the §469 'rental activity' classification. The regulatory foundation of the STR loophole. See our plain-English reference.
The seven material participation tests. Test 3 (more than 100 hours and more than any other individual) is the most common qualifying path for STR owners.
The statute that authorizes the lookback / catch-up depreciation adjustment via Form 3115.
Cited on commercial energy-efficiency angle pages.
Court cases
Landmark Tax Court case establishing that engineering-based cost-seg methodology is acceptable. Foundational precedent for the entire industry.
Multifamily cost-seg case clarifying the line between structural building components and §1245 personal property.
Industry standards
Engineering norms referenced for site-work, foundation, and structural component classifications.
Engineering norms for concrete component lifing.
Data sources
The Bureau of Labor Statistics PPI series is the time-adjustment input that escalates our industry-standard construction cost baseline to current-year dollars by region. Component pricing in our engine is calibrated to nationally-recognized construction cost references.
County assessor data, rental comps, and property characteristics — used to enrich and cross-verify customer-supplied property details.
Building type, landuse, and footprint data for property verification. No personal data; bulk geographic features only.
Geographic context (population, income, building stock) for location pages and benchmarks report.
Our open-data research
Our open-data report (n=412 studies, CC-BY licensed). The benchmark dataset is the source for typical reclassification percentages, year-1 federal tax savings, and US provider pricing distribution claims on this site.
Found something missing or outdated?
Email research@costsegsmart.com. Substantive corrections are dated and noted on the affected page. Tax law updates trigger a full content sweep within 30 days of effective date.