The AmeriSouth Case: What a Tax Court Loss Teaches Investors About Cost Segregation Audit Defense
Every cost segregation provider will tell you their studies are audit ready. Not every provider can tell you why the IRS actually wins some of these disputes, or point to a real case where a taxpayer lost most of a seven figure deduction because the underlying classifications did not hold up. That case exists, it is more than a decade old, and it is still the single most cited precedent in cost segregation practice today. It is AmeriSouth XXXII, Ltd. v. Commissioner, T.C. Memo. 2012-67.
With 100 percent bonus depreciation now permanent under the One Big Beautiful Bill Act, the dollar amounts riding on a single cost segregation study are larger than they have ever been. A study that misclassifies 15 percent of a building's basis used to mean a modest overstatement spread across a depreciation schedule. Today it can mean claiming several hundred thousand dollars of Year One deduction that does not survive contact with an examiner. AmeriSouth is the roadmap for exactly what goes wrong when a study reaches too far, and it is worth understanding in detail before you order one.
What Happened in AmeriSouth
AmeriSouth XXXII, Ltd. purchased an apartment complex in 2003 for roughly 10.25 million dollars. The partnership hired a cost segregation firm that identified more than a thousand individual building components and reclassified them out of the standard 27.5-year residential rental recovery period and into 5-year and 15-year MACRS categories. Across the 2003 through 2005 tax years, AmeriSouth claimed just over 3 million dollars in depreciation based on that reclassification.
The IRS audited the returns and disallowed roughly 1.08 million dollars of the claimed deductions, arguing that most of the reclassified items were structural components of the building rather than personal property or land improvements. AmeriSouth took the dispute to Tax Court. The court sided with the IRS on nearly every category in the study, allowing only a small number of the original claims to stand.
This was not a case about an obviously abusive shelter or a taxpayer with no legitimate basis for a study. AmeriSouth owned real rental property and had a genuine argument that parts of the building qualified for shorter recovery periods. The problem was how far the study pushed the classifications, and the quality of the analysis behind the categories that got disallowed.
The Twelve Categories the Court Reviewed
The Tax Court worked through twelve categories of components that AmeriSouth had reclassified: site preparation and earthwork, the water distribution system, the sanitary sewer system, the gas line, site electric, special HVAC, special plumbing, special electric, finish carpentry, millwork, interior windows and mirrors, and special painting.
Almost all of these categories involve infrastructure that serves the entire building or the entire property rather than a specific tenant improvement or a piece of readily removable equipment. Water distribution, sanitary sewer, gas lines, and site electric are the systems that make an apartment complex habitable in the first place. The court found that this kind of core infrastructure is a structural component of the building under the applicable Treasury regulations, not personal property, regardless of how the cost segregation firm had labeled it in its report.
Only a handful of items across the twelve categories survived. The lesson is not that these categories can never contain any properly reclassified cost. It is that AmeriSouth's study treated the general presence of these systems as sufficient justification for wholesale reclassification, without the item by item engineering analysis that distinguishes a removable fixture serving a specific unit from a building-wide utility system.
The Six-Factor Test Courts Still Use
To decide whether an item is a structural component of a building or personal property eligible for a shorter recovery period, the Tax Court applied the same framework it has used since Whiteco Industries, Inc. v. Commissioner in 1975. Whiteco laid out a set of factors for distinguishing tangible personal property from a structural component under the Treasury regulations governing depreciable property, and cost segregation practice has built on that framework ever since.
In broad terms, the factors ask whether the property can be and has actually been moved, whether it was designed and built to remain permanently in place, how the circumstances point to the intended length of time it will stay affixed, how much work and damage removal would involve, and the manner in which the item is physically attached to the building or the land. An item that would need to be cut out of a wall, that was installed as part of the original construction with no intention of ever moving it, and that serves the building's basic function as a habitable structure is going to fail this test even if a report labels it as personal property.
This is the same analytical framework endorsed in the IRS Cost Segregation Audit Techniques Guide, which examiners are trained to use when reviewing a study. A report that does not walk through this kind of factor-by-factor analysis for its more aggressive classifications is a report that has not actually done the underlying legal work, no matter how detailed the spreadsheet looks.
The Ownership Problem the Case Also Raised
Beyond the structural component question, the IRS also challenged whether AmeriSouth was entitled to depreciate certain assets at all, questioning whether the partnership actually owned some of the property it was claiming deductions on. This is a separate and often overlooked failure point in cost segregation studies. A study can correctly classify an item's recovery period and still generate a bad deduction if the taxpayer claiming it does not hold the depreciable interest in that asset, for example when infrastructure sits on land or easements controlled by a utility or a municipality rather than the property owner.
A properly prepared study confirms ownership and the depreciable basis of each component before assigning a recovery period, not after. This step is easy to skip and rarely shows up in marketing materials, but it is exactly the kind of issue that surfaces during an actual audit.
Why This Case Still Matters in 2026
AmeriSouth is more than ten years old, but nothing about the underlying legal framework has changed. Treasury regulations defining structural components have not been rewritten, and the Whiteco factors remain the operative test. What has changed is the incentive to push the boundaries of a study, and the exposure if you do.
Under the OBBBA, 100 percent bonus depreciation is now permanent for qualifying property, which means every dollar reclassified into a 5-year, 7-year, or 15-year category is deductible in full in Year One rather than spread across a multi-year schedule. That makes an aggressive study more tempting, because the immediate cash benefit of an extra 10 or 15 percent of building basis reclassified is larger than it would have been under a phased bonus depreciation schedule. It also means the immediate exposure if the IRS disallows those same items is larger, because the full amount was already claimed in a single year rather than trickling out over a decade.
In practice, this means the quality gap between a defensible engineering-based study and an aggressive one matters more today than it did when AmeriSouth was decided, not less. A study that reclassifies 30 percent of a building's basis by treating utility infrastructure and structural systems as personal property is not finding you extra money. It is setting up a future dispute over money you may have to pay back with interest and, depending on the facts, penalties under IRC Section 6662 for a substantial understatement of tax.
What a Defensible Study Looks Like By Comparison
The studies that hold up on audit share a few characteristics that AmeriSouth's did not. They apply the Whiteco factors, or an equivalent structural component analysis, to individual items rather than entire categories. A kitchen refrigerator and a building's central water main both technically sit inside the same twelve category framework the AmeriSouth court reviewed, but they are not remotely similar under a component by component test, and a rigorous study treats them differently.
They also document the analysis in writing. The IRS Cost Segregation Audit Techniques Guide specifically instructs examiners to look for a report that explains its methodology, not just a summary table with dollar amounts next to asset classes. A study that shows its work, including photographs, blueprints, invoices tied to specific components, and a written rationale for each classification that could plausibly be challenged, is the study that survives an examination. A study that hands you a spreadsheet with categories and percentages and no supporting analysis is the study that looks exactly like the one AmeriSouth lost with.
Finally, defensible studies are conservative about the categories that AmeriSouth shows are genuinely risky. Site electric, water and sewer infrastructure, gas lines, and other building-wide utility systems are treated as structural components unless there is a specific, documented reason a particular segment serves an individually removable purpose. This is not a matter of leaving money on the table. It is a matter of not claiming money that was never actually available in the first place.
What This Means for Your Study
If you are evaluating a cost segregation provider, ask directly how the firm handles the categories AmeriSouth lost on: site utilities, special electric and plumbing systems, and finish work like millwork and carpentry. A firm that has a clear, conservative, well-documented answer for how it treats these categories is a firm that understands the case law. A firm that promises an unusually high reclassification percentage without being able to explain the component-level basis for it is a red flag, regardless of how the sales pitch is framed.
None of this means cost segregation is risky or that the deductions are not real. The vast majority of properly prepared, engineering-based studies never get audited, and the ones that do generally hold up, because the underlying methodology matches what AmeriSouth and the IRS Cost Segregation Audit Techniques Guide both describe as the correct approach. The case is not a reason to avoid a study. It is a reason to be selective about who prepares it.