What Happens If the IRS Disallows a Cost Segregation Study?

What actually gets questioned, and what doesn't

It helps to separate two different things owners sometimes conflate. One is whether cost segregation applies to a given building at all, a question settled by Hospital Corporation of America v. Commissioner (109 T.C. 21, 1997) and not something a modern exam revisits. The other is whether a specific component in a specific study was classified correctly, which remains a live, ordinary part of any depreciation-related exam, the same way an examiner might question any other deduction's supporting facts.

When a cost segregation study comes up during an exam, it is almost always the second kind of question: did this particular electrical run actually serve specific equipment separately from the building, does this particular decorative lighting item really qualify for 5-year treatment, is the paving allocation supported. Those are component-level questions specific to that building, not method-level ones about cost segregation generally.

The exam process in plain terms

A cost segregation study typically surfaces in an exam because it produced a large first-year deduction, section 481(a) catch-up on a look-back study or an unusually large increase in depreciation expense. The examiner requests the study itself along with its supporting workpapers, the documentation showing how each reclassified component was identified and costed. See what the IRS's own Audit Techniques Guide looks for in that documentation.

From there, the examiner reviews the workpapers against the guide's quality elements: component-level detail, a documented cost allocation method, and consistency with the building's actual construction. Where the documentation supports the classification, that item generally stands. Where it does not, or where a class life looks aggressive relative to the property, the examiner can propose reclassifying that specific item back to its structural schedule (39-year commercial or 27.5-year residential).

What an adjustment actually changes

An adjustment on a specific component changes the depreciation schedule for that item going forward and recalculates the deduction taken in the year(s) affected. It is a recalculation, not a wholesale rejection of the study. A study with a small number of aggressively classified items might see those specific items adjusted while the rest of the reclassification stands. A study built on unsupported percentages across the board is more exposed, because there is less component-level documentation anywhere in it to defend.

This is also why a study typically shifting about 15 to 35% of building basis into faster schedules, varying by property type, is the range worth staying inside absent strong documentation for going higher. A reclassification percentage well outside that range, without a clear component-by-component reason, is the kind of thing that invites a closer look at every item, not just the outliers.

Penalties and reasonable cause

An honest disagreement over how a specific component should be classified, where the taxpayer relied on a documented, engineering-based study prepared in good faith, is different from a position with no supporting basis at all. Accuracy-related penalties generally require more than a good-faith classification dispute; they typically come into play where a position lacked reasonable basis or where the taxpayer failed to act with reasonable cause and in good faith. A well-documented study, prepared by qualified reviewers and relied on reasonably, is the position that supports reasonable cause if a component is later adjusted. This is a general description of how the penalty framework works, not a prediction about any specific return; whether penalties would apply in a given case, and how much they would total, is a legal question for your CPA or tax attorney, not something a cost segregation provider can assess.

Where audit defense of the report fits into this process

When an examiner questions specific classifications, Basis provides full audit defense of the report it produced: the engineers who did the original classification work answer the examiner's questions about those specific items directly, since they are the ones who know why a given component was classified the way it was. That is defense of the study's technical content. It is not representation of the taxpayer in the broader exam; the client's CPA continues to handle that relationship and the rest of the return. The precise boundary between those two roles is laid out at what cost segregation audit defense actually means.

Why documentation quality is the entire story

Put together, the pattern is consistent: the method is not in question, specific components can be, and how well those components are documented determines the outcome far more than which firm produced the study or how large the deduction was. A $599,678 first-year deduction on a Free-Standing Restaurant study, at a 66.6:1 ratio to its $9,000 fee, is not inherently riskier than a smaller deduction, provided the documentation behind each reclassified kitchen component, the ranges, the hoods, the walk-in coolers, the specific electrical serving them, holds up the same way a smaller study's documentation would.

This is also the reason to evaluate any provider, including Basis, on documentation practices rather than on the size of the number they project. See the red flags worth watching for when vetting a cost segregation firm, from either side of the table.

Getting a study designed to hold up under exactly this process

A free Preliminary Benefit Estimate at /qualify starts from an engineering-based approach that documents each component as it is classified, the same documentation an examiner would eventually review if the study were ever questioned.

Whether a specific exam outcome, penalty exposure, or reasonable-cause argument applies to your return is a question for your CPA. What a documented, engineered study provides is the paper trail that process runs on, component by component, from the first classification decision through whatever question eventually gets asked about it.

Frequently asked questions

Can the IRS reject cost segregation entirely?

The method itself is settled law since Hospital Corporation of America v. Commissioner in 1997. An examiner can question specific component classifications within a study, but does not reject the underlying method as invalid.

What triggers an IRS review of a cost segregation study?

There is no single published trigger. A large first-year deduction, a section 481(a) catch-up on a look-back study, or an unusually high reclassification percentage relative to a property's type are the kinds of things that can draw a closer look during a broader exam.

Does a disallowed component mean I owe back taxes plus penalties?

An adjustment to a specific component generally means recalculating the depreciation and any tax difference for the affected years. Whether penalties apply depends on documentation and reasonable cause, a legal determination for your CPA or tax attorney, not something a general description can resolve for your specific return.

Who handles an IRS question about my cost segregation study?

The firm that produced the study defends its own report's technical content, meaning the engineers explain their classifications. Your CPA continues to represent you in the exam itself and the rest of your return.