What Makes a Quality Cost Segregation Study? The ATG's Checklist

The 2025 IRS Cost Segregation Audit Technique Guide does not define a quality cost segregation study by its final percentage alone. The ATG says a quality study is both accurate and well documented, with support for property classification, legal reasoning, and cost basis. It identifies 13 principal elements that help establish that quality. For investors, this creates a practical question: what should actually be inside a defensible cost segregation study? The answer is much broader than a schedule showing accelerated depreciation.

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Key Takeaways

• The ATG defines a quality study as accurate and well documented, with support for classification, legal rationale, and cost basis.
• A quality study documents its methodology, evidence, engineering procedures, interviews, cost development, and asset organization.
• Quality documentation helps investors and examiners understand how the study reached its classifications and cost allocations.
• The 13 principal elements apply across different property types and methodologies, even though the specific evidence may vary.
• Investors should look beyond the accelerated percentage and ask how the underlying costs and classifications were developed.
• A study can reconcile numerically while still leaving important questions unanswered if the supporting cost and classification evidence is incomplete.
• A quality study is not just a tax result. It is a documented chain of engineering, cost, and classification evidence.

What Is a Quality Cost Segregation Study?

The ATG says a quality cost segregation study is a study that is both accurate and well documented.

The ATG identifies three foundational requirements for a cost segregation study and report:

• Classify assets into appropriate property classes.
• Explain the rationale, including legal citations, for classifying assets as § 1245 or § 1250 property.
• Substantiate the cost basis of each asset and reconcile total allocated costs to total actual costs.

These requirements establish the foundation.

The 13 principal elements then explain what a quality study should contain to support that foundation.

The ATG identifies:

1. Preparation by an Individual with Expertise and Experience
2. Detailed Description of the Methodology
3. Use of Appropriate Documentation
4. Interviews Conducted with Appropriate Parties
5. Use of a Common Nomenclature
6. Use of a Standard Numbering System
7. Explanation of the Legal Analysis
8. Determination of Unit Costs and Engineering “Take-Off”
9. Organization of Assets into Lists or Groups
10. Reconciliation of Total Allocated Costs to Total Actual Costs
11. Explanation of the Treatment of Indirect Costs
12. Identification and Listing of § 1245 Property
13. Consideration of Related Aspects

The ATG also makes clear that there is no single prescribed format for cost segregation studies. A report may be brief or extensive, depending on the property and methodology.

Quality therefore does not mean length.

It means whether the study accurately and clearly supports its conclusions.

How Does a Quality Study Begin?

The first element is the person preparing the study.

The ATG says cost segregation requires knowledge of both the construction process and tax law involving property classifications for depreciation purposes. It notes that a construction engineer will generally provide a more reliable study than someone without an engineering or construction background, while also emphasizing experience in cost estimating, allocation, and applicable tax law.

A quality study should identify the preparer and reference the preparer's credentials, experience, and expertise in cost segregation.

This matters because cost segregation is not purely a tax exercise.

It requires someone to understand what was built, how it was built, what the assets do, how their costs were developed, and how the tax rules apply.

That combination is central to engineering-based cost segregation.

Why Must the Methodology Be Explained?

The ATG says a quality study always describes the methodology used and details the steps taken to classify assets and determine costs.

The report should therefore allow a reviewer to understand:

• What methodology was used
• What property was analyzed
• What records were reviewed
• How assets were identified
• How costs were developed
• How classifications were determined
• How the final allocations were reconciled

The ATG recognizes several common approaches, including detailed engineering from actual cost records, detailed engineering cost estimates, survey or letter, residual estimation, sampling or modeling, and rule of thumb.

A study can use a variant or combination of methods.

That makes the explanation even more important.

The reader needs to understand what the preparer actually did, not simply what a methodology might be called.

Why Is Documentation So Important?

The ATG says a quality study uses the best available documentation to classify assets and determine costs.

The available evidence can differ significantly between a newly constructed property and an acquired property.

For new construction, the documentation may include:

• Construction contracts
• Architectural drawings
• Engineering drawings
• Specifications
• Pay applications
• Change orders
• Invoices
• Contractor records
• Other contemporaneous construction records

For acquired property, the original construction records may be limited or unavailable.

The ATG recognizes that the amount of available construction information can range from extensive documentation to nothing more than the purchase price.

The methodology should adapt to the evidence that actually exists.

That does not mean lowering the standard of support.

It means using the best available evidence and explaining how it was used.

Why Do Interviews Matter?

Engineering documentation does not always answer every question.

The ATG therefore includes interviews as one of the principal quality elements.

Interviews can help establish:

• How a property is used
• What specific systems support
• What equipment performs
• How a facility operates
• What construction decisions were made
• Why certain components were installed

For example, a drawing may show a dedicated mechanical system.

An interview can help explain whether that system serves the building generally or supports a specific business process.

That distinction can matter to classification.

CostSegRx engineers use field analysis and documentation together because the physical asset, its function, and its cost evidence need to tell the same story.

Why Does Nomenclature Matter?

The ATG specifically warns against creative or misleading descriptions of property.

A quality study should use common, clearly understood terminology consistent with blueprints and other project documents.

This may sound minor.

It is not.

Consider two descriptions:

Building water piping

versus:

Process piping

The second description could suggest a different classification question.

The ATG gives similar examples of potentially misleading terminology.

Using the actual terminology from construction documents helps the reviewer understand what the asset really is.

Good nomenclature reduces ambiguity.

Why Does the Numbering System Matter?

The ATG identifies the use of a standard numbering system as another quality element.

It specifically points to the Construction Specification Institute, or CSI, Master Format as an example.

A consistent numbering system can connect the cost segregation study to:

• Construction documents
• Contract bid documents
• Pay requests
• Building systems
• Property groups

This creates a common language between the construction records and the tax analysis.

It also makes the study easier to review.

For an investor, this means the report is not just a collection of tax categories.

It can be traced back to the way the property was actually constructed.

Why Does the Legal Analysis Matter?

The ATG says a quality study contains a thorough legal analysis, including relevant citations, supporting § 1245 property classifications.

The legal analysis should address the facts of the property.

This is important because the ATG recognizes that classification disputes can be intensely factual.

Different cases may appear inconsistent until the specific facts and circumstances are examined.

A quality study therefore does not simply state:

“This is § 1245 property.”

It explains:

• What the asset is
• What it does
• How it is connected to the property
• What legal standard applies
• Why the facts support the classification

That is where engineering and tax analysis intersect.

What Is an Engineering Take-Off?

Once property items are identified and assigned to property classes, their costs must be determined.

The ATG describes the breakdown of total project costs into individual property units as an engineering “take-off.”strong>

A quality study documents the take-off and shows the derived unit costs.

For new construction, the cost of property items can often be obtained from actual cost records.

When actual costs are unavailable, the costs must be estimated.

The ATG says individual property units should be clearly identified or highlighted on as-built blueprints when appropriate.

This creates an important connection:

Physical property → quantity → unit cost → allocated cost

The take-off is where the engineering analysis becomes a cost allocation.

Why Are Assets Organized Into Lists or Groups?

A quality study needs a clear way to organize the property it analyzes.

The ATG describes property unit summaries and property unit details as examples of how assets can be organized.

A unit group may combine individual assets that together form a larger assembly treated as a single asset.

For example:

Kitchen Equipment - Plumbing

might contain individual assets such as:

• Floor drain
• Grease trap
• Sanitary piping
• Sink
• Water supply piping

The important point is traceability.

The reviewer should be able to understand what is included in the group and how its cost basis was determined.

The ATG notes that abbreviated methodologies may not use formal unit-group schedules, but assets should still be identified, supported, and documented.

Why Must the Study Reconcile to Actual Costs?

Reconciliation is one of the most important quality controls in the ATG.

The total allocated costs should reconcile to the total actual costs.

This prevents the study from creating a tax allocation that is disconnected from the property's actual financial records.

For example, suppose the taxpayer's records show:

Total project cost: $10 million

The study allocates:

• Land improvements: $1 million
• 5-year property: $1.5 million
• 15-year land improvements: $500,000
• Building: $7 million

The allocation totals:

$10 million

That is a basic mathematical reconciliation.

But a quality study should also explain how those numbers were developed and what evidence supports each allocation.

Reconciliation is therefore both a mathematical and documentary control.

The ATG also says study results should be easily reconcilable to the taxpayer's depreciation or fixed asset schedules.

Why Must Indirect Costs Be Explained?

Indirect costs can affect multiple property classes.

The ATG says a quality study explains the purpose of each indirect cost and describes its allocation.

Some indirect costs relate specifically to land.

For example:

• Surveying and subdivision costs
• General grading

Other costs may be allocated across property classes.

The ATG gives examples such as:

• Building permits
• General conditions
• Contractor overhead and profit

Some indirect costs may also relate directly to personal property.

For example, specialized consulting for computer wiring or process engineering may be associated with a specific system.

The point is not to apply one universal indirect-cost percentage.

The point is to understand what the cost represents and explain why it was allocated where it was.

Why Must § 1245 Property Be Identified?

The ATG says a quality study lists § 1245 property, including amounts, and identifies property originally classified as § 1250 property that was reclassified to § 1245 property.

This is central to cost segregation.

The purpose of the study is not simply to create a percentage of accelerated property.

It is to identify specific property that belongs in different recovery periods under the applicable tax rules.

The report therefore needs to show what property was identified and how its classification was reached.

That is especially important for assets near the boundary between building components and separate property.

What Related Issues Should a Quality Study Address?

The ATG's final principal element is consideration of related issues.

The ATG specifically identifies:

• § 263A
• Changes in accounting method
• Sampling techniques

A quality study should address these issues when applicable.

For example, the ATG explains that § 263A requires capitalization of direct costs and certain indirect costs allocable to property produced by the taxpayer, including self-constructed assets and property built under contract.

The ATG also discusses changes in accounting method associated with changing depreciation classifications or recovery periods.

And when sampling is used, the study should address the population, population size, stratification, and sampling error.

These issues can sit outside the main asset schedule, but they can still affect the quality of the overall analysis.

What Does a Quality Study Look Like in Practice?

The ATG does not prescribe one report format.

Instead, a quality report can contain several complementary sections.

The ATG identifies:

• Summary letter or executive summary
• Narrative report
• Schedule of assets
• Schedule of direct and indirect costs
• Schedule of property units and costs
• Engineering procedures
• Statement of assumptions and limiting conditions
• Certification
• Exhibits

The narrative should explain the property, its use, the methodology, the legal analysis, and the data sources used.

The schedules should organize the assets and costs.

The engineering procedures should explain how property-unit costs were developed.

The exhibits can include client cost sources, cost-source reconciliation, photographs, and videos.

This structure creates multiple layers of support.

Why Does Study Quality Matter to Investors?

Study quality matters because the tax result is only useful if the underlying analysis can be understood and supported.

A quality study helps an investor understand:

• What property was analyzed
• What assets were classified
• How costs were developed
• What documentation supports the conclusions
• How the result reconciles to the investor's records

That matters during ownership.

It can matter when the property is refinanced.

It can matter when ownership changes.

It can matter when a CPA or tax advisor reviews the depreciation schedules.

And it can matter if the study is examined by the IRS.

The ATG specifically says quality studies can expedite the Service's review and minimize the audit burden on taxpayers, practitioners, and examiners.

How Should Investors Evaluate a Study?

An investor does not need to become a cost segregation engineer to ask better questions.

Start with the evidence.

Ask:

Who prepared the study?

What methodology was used?

What documents were reviewed?

Were interviews conducted?

Are asset descriptions consistent with the construction records?

How were unit costs developed?

Where are the engineering take-offs?

How were indirect costs treated?

Does the study reconcile to actual project costs?

Can the § 1245 classifications be traced to supporting facts and legal analysis?

These questions shift the conversation away from:

“How much accelerated depreciation did the study produce?”

and toward:

“How well does the study support the result?”

That is the better investor question.

Illustrative Example

Illustrative example only. Figures shown are estimated for demonstrative purposes only. Actual land allocations, asset classifications, depreciation, and tax results depend on the specific property, supporting documentation, engineering analysis, and taxpayer circumstances.

Assume two investors each own a hypothetical commercial property with a depreciable basis of:

$10 million

Both studies identify:

$2 million of accelerated property

At first glance, the studies appear identical.

But the supporting documentation is different.

	Study A	Study B
Accelerated property	$2 million	$2 million
Engineering methodology explained	Yes	Limited
Property-specific documentation	Detailed	Limited
Cost reconciliation	Yes	Unclear
Asset-level support	Detailed	Generalized

The numerical result is the same.

The quality of the evidence is not.

That distinction is the point of the ATG's quality-study framework.

A quality study is not defined solely by how much property was moved into shorter recovery periods.

It is defined by whether the classifications and costs are accurately and adequately supported.

What Should the Final Report Contain?

The ATG describes a quality report as the document that reflects the study's methodology and conclusions.

Because there is no standard prescribed format, the report can vary in structure and length.

But the ATG identifies several useful components.

The summary identifies the preparer, date, taxpayer, subject property, and property units classified.

The narrative explains the property's physical characteristics, use, legal description, methodology, supporting authorities, and data sources.

The schedule of assets identifies the assets that are the focus of the study and should generally tie to depreciation records.

The schedule of direct and indirect costs identifies project costs and explains indirect-cost allocations.

The schedule of property units and costs provides the detailed property classifications and costs that become the basis for computing depreciation.

The engineering procedures explain how property-unit costs were developed and identify records reviewed, estimating techniques, inspections, interviews, nomenclature, and numbering systems.

The report can also include assumptions, limiting conditions, certification, and exhibits.

How Does This Fit Into the ATG Encyclopedia?

This article is the gateway to the ATG's Quality of Study / Cost Development section.

The next articles can examine the individual elements in greater depth:

Quality Study

↓

Cost Reconciliation

How the study ties back to actual costs.

↓

Engineering Take-Offs

How property costs are developed and documented.

↓

Direct and Indirect Costs

How project costs are assigned to property classes.

↓

Acquired Property

How costs are reconstructed when original records are unavailable.

This structure mirrors the ATG itself.

The purpose is not to create five disconnected articles.

It is to build a reference system where investors can move from the overall definition of study quality into the specific engineering and cost-development questions that support it.

Engineering Principle

A Quality Study Is a Documented Chain of Engineering, Cost, and Classification Evidence.

The 2025 ATG does not define study quality by a particular percentage of accelerated property.

It defines quality through accuracy, documentation, methodology, classification reasoning, cost support, and reconciliation.

The 13 principal elements reinforce that framework.

The preparer needs appropriate expertise.

The methodology needs to be explained.

The documentation needs to support the analysis.

The asset descriptions need to be clear.

The legal analysis needs to address the facts.

The engineering take-offs need to support the costs.

The indirect costs need to be explained.

The final allocations need to reconcile.

That is what makes the result understandable and supportable.

A quality study is not just a tax result. It is a documented chain of engineering, cost, and classification evidence.