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IRS ITG Audit Techniques Chapter 3

Chapter 3 – Cost Segregation Methodologies

Note: Each chapter in this Audit Techinques Guide (ATG) can be printed individually. Please follow the links at the beginning or end of this chapter to return to either the previous chapter or to proceed to the next chapter or select a chapter from the Table or Contents on the left of this page.


Cost segregation studies are conducted for a variety of reasons (e.g., income tax, financial accounting, insurance purposes, property tax). For income tax purposes, a cost segregation study involves the allocation (or reallocation) of the total cost (or value) of property into the appropriate property classes in order to compute depreciation deductions. The results of a study are typically summarized in an accompanying report, although there is no standard format for either the study or the report.

The methodology utilized in allocating total project costs to various assets is critical to achieving an accurate cost segregation study. Some of the more common methodologies, and their potential drawbacks, are summarized in this chapter. This discussion should assist the examiner in evaluating the accuracy of a particular study and in performing a risk analysis with respect to the depreciation deductions based on that study.


Various methodologies are utilized in preparing cost segregation studies, including:

  1. Detailed Engineering Approach from Actual Cost Records
  2. Detailed Engineering Cost Estimate Approach
  3. Survey or Letter Approach
  4. Residual Estimation Approach
  5. Sampling or Modeling Approach
  6. “Rule of Thumb” Approach

Examiners should not necessarily expect to see these terms mentioned in a study or in a report. Methodologies will also be described in varying detail in different reports. However, based on the information in this chapter, an examiner should be able to recognize the attributes of a given study and identify the methods or approaches used (and also identify the potential drawbacks). It should also be noted that other methodologies may be used, although most are merely derivatives of those enumerated above.


The following discussion takes a closer look at the main components and attributes of each of the methodologies listed above. Keep in mind that these are the steps normally taken in the preparation of a cost segregation study. The examiner’s responsibility is to review the steps taken and evaluate the accuracy of the study, as will be discussed in Chapter 5, “Review and Examination of Cost Segregation Studies.”

Detailed Engineering Approach From Actual Cost Records

The detailed engineering approach from actual cost records, or “detailed cost approach,” uses costs from contemporaneous construction and accounting records. In general, it is the most methodical and accurate approach, relying on solid documentation and minimal estimation. Construction-based documentation, such as blueprints, specifications, contracts, job reports, change orders, payment requests, and invoices, are used to determine unit costs. The use of actual cost records contributes to the overall accuracy of cost allocations, although issues may still arise as to the classification of specific assets.

This approach is generally applied only to new construction, where detailed cost records are available. For used or acquired property and for new projects where original construction documents are not available, an alternative approach (e.g., the “detailed engineering cost estimate approach”) may be more appropriate.

The detailed cost approach typically includes the following activities:

  1. Identify the specific project/assets that will be analyzed.
  2. Obtain a complete listing of all project costs and substantiate the total project costs.
  3. Inspect the facility to determine the nature of the project and its intended use.
  4. Photograph specific property items for reference. Request previous site photographs that illustrate the construction progress as well as the condition of the property before the project began.
  5. Review “as-built” blueprints, specifications, contracts, bid documents, contractor pay requests, and other construction documentation.
  6. Identify and assign specific project items to property classes (e.g., land, land improvements, building, equipment, furniture and fixtures, and other items of tangible personal property).
  7. Prepare quantitative “take-offs” for all materials and use payment records to compute unit costs.
  8. Apply unit costs to each project component to determine its total cost. Reconcile total costs obtained from quantitative take-offs to total actual costs.
  9. Allocate indirect costs, such as architectural fees, engineering fees, and permits, to appropriate assets.
  10. Group project items with similar class lives and placed-in-service dates to compute depreciation.

The detailed cost approach is the most time consuming method and generally provides the most accurate cost allocations. However, the examiner should recognize that the proper classification and costs of § 1245 property could still be an issue with this method.

Detailed Engineering Cost Estimate Approach

The detailed engineering cost estimate approach (or detailed estimate approach) is similar to the detailed cost approach. The difference is that the detailed estimate approach estimates costs, rather than using actual costs. This approach is used when cost records are not available or for an acquisition when the purchase price must be allocated.

The detailed estimate approach is methodical, relying on solid documentation and utilizing construction-based documents such as blueprints, specifications, contracts, job reports, change orders, payment requests, invoices, appraisals, etc. When estimates are required, they are based on costing data, either from contractors or from reliable published sources (e.g., R. S. Means or Marshall Valuation Service). The sources of estimating data are clearly referenced, including identification of the specific volume, page, and item number. Further, the same estimating techniques and unit cost data sources are used for all of the items that comprise the actual cost.

In essence, the steps for this approach are the same as the detailed cost approach, except for Step 7 (in which costs come from contractor estimates or estimating guides). However, if detailed cost estimates are prepared by qualified individuals, and the estimates are reconciled to actual costs, then reasonably-accurate cost allocations are possible.

Survey Or Letter Approach

The survey or letter approach is an alternative method for estimating costs. In this approach, contractors and subcontractors are contacted via a survey or letter to provide information on the cost of specific assets that they installed on a particular project. These costs are then used in one of the engineering approaches or in the residual estimation approach (discussed in the following section). Cost allocation using the survey approach involves the following steps:

  1. Complete Steps 1 – 6 of the detailed cost approach to identify the specific property items that require cost estimates. Estimates should be reconciled to an actual cost if possible [either to an overall project cost or to an individual system cost (e.g., plumbing, electrical)].
  2. Divide property items by contractor and/or subcontractor.
  3. Ask contractors and/or subcontractors to provide the quantities and prices of specific property items.
  4. Use unit cost estimates obtained from the surveys to determine and allocate property costs.

In situations where the contractor provides actual cost data, the allocations may be reasonably reliable. However, when contractor data is obtained from other sites or projects, the data may not be comparable or reliable. The amount of detail provided by different contractors may also vary. The wide disparity in cost estimation methods dictates the use of caution to ensure that the total allocated costs do not exceed the actual total project cost.

Residual Estimation Approach

The residual estimation approach is an abbreviated method in which only short-lived asset costs (e.g., 5- or 7-year property) are determined. Short-lived asset costs are added together and then subtracted from the total project cost. The remaining or “residual” cost is then simply assigned to the building and/or other long-lived assets. Although this method is simpler and less time consuming than the engineering approaches, it can also be less accurate.

It should be recognized that this method generally does not reconcile project costs. In general, residual costs are not estimated or checked for reasonableness. A proper and “reasonable” residual cost should always be determined and then added back to the total of all short-lived asset costs to check if the total project cost is reconciled.

It should also be understood that different estimation techniques for short-lived assets can produce a skewed result in favor of § 1245 property (e.g., § 1245 property based on single-unit costs for high quality construction, while the building is based on gross square footage).

Sampling Or Modeling Approach

The sampling or modeling approach uses a created model (or template) to analyze multiple facilities that are nearly identical in construction, appearance and use (e.g., fast food chains and retail outlets). The use of sampling minimizes resources and costs compared to conducting studies on all properties.

Typical steps are:

  1. Stratify properties by type of facility (e.g., free-standing facility, mall location, leased or owned property, etc.).
  2. Perform a cost segregation study on a sampling of properties within each stratum.
  3. Based on the results in Step 2, develop a standard model for each type of facility.
  4. Apply the costs derived from the model(s) to the population on a percentage basis. For example, the model may indicate that 10% of the project costs are allocable to 5-year property. This same percentage is then applied to each facility within the same stratum.

A frequent issue is the accuracy of the sampling results. In some cases, the sampling method may not be statistically valid. In addition, a population less than 50 could limit the accuracy of a sampling technique, unless an appropriate sampling error is considered. Also, despite the fact that facilities within certain strata may appear to be very similar, variations in building codes, geographic location, and material and labor costs may make it difficult to determine an appropriate model. Statistical sampling is discussed in more detail in Chapter 5, “Review and Examination of a Cost Segregation Study,” and in Appendix Chapter 6.5.

“Rule Of Thumb” Approach

Some cost segregation studies are merely based on a “rule of thumb” approach. In general, this approach uses little or no documentation and is based on a preparer’s “experience” in a particular industry. For example, a preparer will estimate § 1245 property as a fixed percentage of project cost by relying on previously determined “industry averages” (e.g., 40% for a manufacturing facility). An examiner should view this approach with caution, since it lacks sufficient documentation to support its allocation of project costs.


Neither the Service nor any group or association of practitioners has established any requirements or standards for the preparation of cost segregation studies. The courts have addressed component depreciation, but have not specifically addressed the methodologies of cost segregation studies.

The Service has addressed this issue but only briefly, i.e., Revenue Ruling 73-410, 1973-2 C.B. 53, Private Letter Ruling (PLR) 7941002 (June 25, 1979), Chief Counsel Advice Memorandum 199921045 (April 1, 1999). These documents all emphasize that the determination of § 1245 property is factually intensive and must be supported by corroborating evidence. In addition, an underlying assumption is that the study is performed by “qualified” individuals or firms, such as those employing “…personnel competent in design, construction, auditing, and estimating procedures relating to building construction” (PLR 7941002).

Despite the lack of specific requirements for preparing cost segregation studies, taxpayers still must substantiate their depreciation deductions and classifications of property. Substantiation using actual costs is generally preferable to the use of estimates. However, in situations where estimation is the only option, the methodology and the source of any cost data should be clearly documented. In addition, estimated costs should be reconciled back to actual costs or purchase price.


Cost segregation studies are prepared for a variety of reasons (e.g., income tax, financial accounting, insurance purposes, property tax), and many different methodologies and procedures are used. While neither the Service nor any group or association of practitioners prescribes a specific methodology, there are certain approaches (e.g., studies based on actual costs or on proper estimation techniques) that produce more accurate and reliable allocations. Despite the use of one of these more reliable methods, issues may still arise with respect to the proper classification of § 1245 property.

Methodologies that yield accurate cost allocations expedite the Service’s review, saving time and resources for taxpayers, practitioners, and Service examiners alike. A study that is both accurate and well documented is considered (in this ATG) a “quality” cost segregation study. The specific characteristics that comprise a quality study are described in Chapter 4, “Principal Elements of a Quality Cost Segregation Study and Report”.