🇺🇸 Made in America·100% U.S.-Based Team · 24+ Years in Cost Segregation
Somewhere in an office in Ogden, Utah, an IRS examiner sits down with a coffee and a cost segregation study report. The owner is being audited. The study reclassified $340,000 of the property into 5-year, 7-year, and 15-year MACRS property. That triggered $340,000 of Year 1 bonus depreciation. The IRS computer flagged the return.
The examiner does not know the owner. The examiner does not know the building. The examiner has the report in front of him, a return, and one document open on the second monitor. That document is 347 pages long. It is called the Cost Segregation Audit Technique Guide, and the current edition is IRS Publication 5653, dated February 6, 2025.
The next two weeks of the owner's life depend on what the examiner finds in that report when he compares it to the standards in the ATG.
That is the entire game.
Most property owners think the IRS hates cost segregation. They don't. The IRS publishes a 347-page manual explaining exactly how it should be done. The ATG is the most detailed document the IRS publishes on any subject related to building tax classification. It is publicly available. Anyone can read it. The firm that did your study should have read it. If they did not, you have an audit risk you do not need to have.
This article walks you through what the ATG actually says. The six methodologies it identifies. The two it prefers. The four it does not. The reasons that distinction matters. And what you should look for when choosing a cost segregation firm or evaluating a study that has already been done.
The Cost Seg America team has read the ATG. We have read every revision since the 2004 original. We use the methodologies the ATG prefers on every study. The result is 24 years in business, 16,000 studies, 125 IRS audits defended, zero losses, and $0 ever returned. The ATG is the reason that record exists. The rest of this article explains why.
The Cost Segregation Audit Technique Guide was first published in 2004. The IRS issues ATGs in different practice areas to give its examiners a consistent framework for evaluating returns in specialized fields. The cost segregation ATG was written specifically for IRS revenue agents who get a cost segregation study on examination. The current edition is Publication 5653, catalog number 20884M, dated February 6, 2025.
Three things to understand about the ATG.
First, it is not law. The ATG is internal IRS guidance. It tells IRS examiners how to look at studies. It does not create new rules. The underlying law is the Internal Revenue Code, MACRS regulations, and case law including Hospital Corporation of America v. Commissioner and the Whiteco factors. The ATG just tells examiners how to apply those existing rules.
Second, it is public. The ATG is available on the IRS website. You can read it. Your CPA can read it. Your cost segregation firm definitely should read it. Any firm that claims to perform cost segregation studies and does not own a current copy of this document is operating without the most important reference in the field.
Third, it is detailed. The current 2025 edition runs 347 pages. It covers methodology, asset classifications, industry-specific guidance, common audit issues, and dozens of examples. There have been significant updates over the years, including 2017 (electrical distribution systems) and June 2022 (Tax Cuts and Jobs Act and CARES Act revisions). Most property owners do not need to read the whole thing. Anyone who advises on cost segregation absolutely does.
What the ATG accomplishes is consistency. Before the ATG, an examiner in New York might handle a study one way and an examiner in Texas might handle it differently. After the ATG, examiners across the country had a single framework. That framework rewards studies that did the work properly. It punishes studies that did not.
The ATG identifies six general approaches that a cost segregation study can use. They are called Approaches 1 through 6.
Approach 1: Detailed Engineering Approach from Actual Cost Records. This is the highest quality methodology in the ATG. It applies when the property was built or significantly renovated and the owner has the actual construction cost records. The cost segregation engineer takes those construction invoices, change orders, contractor breakdowns, and architect drawings, and assigns every cost to its proper MACRS class. The math at the end matches the documented spend. The classifications are tied to specific invoices. Costs are sorted by Construction Specifications Institute divisions (concrete, masonry, metals, finishes, mechanical, electrical) to establish a clean audit trail from the contractor payment requests through to the final classification.
This is the most defensible kind of study. The examiner can verify every classification against a specific document. There is no estimation involved. The actual cost is the actual cost.
Approach 2: Detailed Engineering Cost Estimate Approach. When actual construction cost records are not available, which is the case on most acquired buildings, Approach 2 is the next best methodology. An engineer performs an engineering analysis of the property. The engineer measures, photographs, and documents every component. Cost estimates for each component are then built using the Replacement Cost New Less Depreciation methodology, with replacement cost data sourced from industry-standard published references: Marshall Valuation Service, R.S. Means Facilities Construction Cost Data, or comparable engineering cost manuals. The system distinguishes Section 1245 tangible personal property (eligible for accelerated depreciation) from Section 1250 real property (the building shell at 27.5 or 39 years).
The result is a component-by-component cost allocation built from a real engineering survey, with cost estimates supported by industry-standard published references. Every classification is documented. Every cost has a source.
Most cost segregation studies on acquired properties use Approach 2. It is the most common high-quality methodology in the field.
Approach 3: Survey or Letter Approach. Approach 3 relies on surveys or letters sent to contractors who originally built the property. The contractor provides cost information for various components. The cost segregation firm uses that information to build the classification. The ATG lists this as an acceptable methodology but notes the documentation is weaker. Contractor letters are not always reliable. Recollection of cost breakdowns from years earlier is imprecise. Studies built on Approach 3 are more vulnerable in audit because the supporting documentation rests on third-party recollection.
Approach 4: Residual Estimation Approach. Approach 4 starts with actual costs for some categories and estimates the rest as a residual. If actual data exists for, say, 60 percent of the components, the remaining 40 percent is estimated by working backward from the known total. This approach is sometimes appropriate when partial cost data exists. It is less rigorous than Approaches 1 and 2. The estimated portion lacks the same documentation strength as the actual portion.
Approach 5: Sampling or Modeling Approach. This is the methodology most commonly used by software-driven cost segregation services. Approach 5 takes a small sample of components from the property, applies industry-average percentages from a database, and produces a category-level reclassification. The output is fast to produce. The numbers may look reasonable. The supporting analysis is thin. The ATG specifically discusses the limitations of Approach 5. Studies using this method are more vulnerable in audit because the classifications rest on industry averages rather than property-specific engineering analysis.
Approach 6: Rule of Thumb Approach. The weakest methodology in the ATG. Rule of thumb means the cost segregation firm applies blanket percentages to entire categories without component-level analysis. The ATG explicitly identifies Approach 6 as the lowest-quality methodology and most vulnerable in audit. There is essentially no documentation behind the numbers.
The ATG does not say all six methodologies are equal. It explicitly identifies Approaches 1 and 2 as the preferred methodologies. The reason is documentation.
When an examiner opens a study built on Approach 1 or 2, the examiner sees a component-by-component schedule showing every reclassified item, specific cost data supporting each component, engineering documentation of why each component qualifies for the assigned MACRS class, an engineering review report or actual cost records as the foundation, and citations to the Whiteco factors and relevant case law. The examiner can verify the work. The classifications are tied to documents.
When an examiner opens a study built on Approach 5 or 6, the examiner sees category totals with no component-level detail, industry-average percentages applied to category groups, little or no engineering documentation, and no supporting engineering review. The examiner cannot verify specific classifications. The numbers might be right. The supporting analysis is not there.
A study built on Approaches 1 and 2 will typically identify $60,000 to $150,000 more per $1 million of depreciable basis than a study built on Approach 5 or 6. The Approach 1 and 2 study finds the actual qualifying components. The Approach 5 study estimates the category totals. The first methodology produces more deduction and more documentation. The second produces less of both.
You get both more money and more audit protection from the better methodology. The choice is not money versus safety. The choice is doing the work right or not.
The ATG gives you a simple framework for evaluating any cost segregation firm. Ask three questions.
Which IRS methodology will you use on my study? The answer should be Approach 1 or Approach 2. If the firm says "Approach 5" or "software-driven" or "AI-powered" or anything similar, you are getting the weakest methodology the ATG identifies.
Will you perform an engineering analysis? Approach 2 requires an engineering analysis of the property. A qualified engineer evaluates the building and its components through review of construction records, design documentation, dimensional data, and property specifications, applying the Whiteco 6-factor test to every reclassified item. If the firm performs the entire study from cursory document review or software-generated estimates without proper engineering analysis, the study is not running Approach 2. It is running something weaker.
Will the report cite the Whiteco factors and the HCA case? A study built on Approaches 1 and 2 walks every reclassified component through the Whiteco analysis from the 1975 Whiteco Industries case and references the Hospital Corporation of America v. Commissioner ruling from 1997. These are the legal foundations of cost segregation. A serious study cites them. A weak study does not.
The IRS published a 347-page document explaining exactly how to do cost segregation studies. It identifies two methodologies as preferred. It identifies four methodologies as weaker. It walks through specific industry guidance. It flags common audit issues.
If you are about to do a cost segregation study, you have one main decision to make. You decide whether your study runs on the methodology the IRS itself identifies as preferred, or on a faster, cheaper, weaker methodology. The numbers may come out similar on the report. The audit defense will not.
The Cost Seg America team uses Approaches 1 and 2 on every study. Not most. Every. We have done so for more than 24 years. 16,000 studies. 125 IRS audits defended. Zero losses. $0 ever returned to the IRS. Every study is engineered, not estimated. The average first-year savings across those 16,000+ completed studies is $438,511. Our reports walk every component through the Whiteco analysis, cite the HCA case, and tie classifications to specific engineering documentation.
The cheap competitor in the cost segregation market is the $2,900 study. Software-driven. No engineering analysis. Approach 5 or Approach 6 at best. These studies recover $60,000 to $150,000 less per $1 million of property than a properly built engineered study, and they do not hold up the same way when an IRS examiner opens the file. Made in America, by Americans, is not just brand positioning. It is what the standard looks like.
Email: info@costsegamerica.com
Phone: 1-888-365-5023
Online: costsegamerica.com/free-proposal
The IRS told everyone how to do this work. The Tax Court told everyone the work holds up when it is done right. The OBBBA made the math the strongest it has ever been. The only question is whether your specific study is the kind the ATG describes, or the kind that gets disallowed when the examiner opens the file in Ogden, Utah, with a coffee and Publication 5653 open on the second monitor.
