Short answer
Cost segregation software comes in two kinds, and the difference matters more than the price. The first kind is a tool: it organizes documents, measures from digital drawings, applies unit costs the user supplies, tracks classifications the user decides, and produces a reconciliation and a report from a practitioner's work. Practitioners use tools like that every day. The second kind is a product that takes an address, a property type, a price and a questionnaire, and returns a "study." That product cannot do what the IRS's Audit Techniques Guide describes a quality study doing: inspect the site, document the components, decide each classification on its function and the law, price from records or documented take-offs, and reconcile to the basis. It applies a percentage with extra steps, which the guide treats as the least reliable approach. The IRS prescribes no qualifications for preparers, so nothing stops an owner from using such a product; the question is whether the output would survive the requests an examiner is told to make. This article explains how to tell the two kinds apart and what to ask. It is general education, not tax advice.
What the IRS expects, and what software can supply
| Element of a quality study | A tool in a practitioner's hands | A questionnaire product |
|---|---|---|
| Preparer with expertise and experience, identified | The practitioner | Often no identified individual |
| Site inspection and interviews | Done by a person; photos and notes keyed in the tool | Not performed |
| Documentation | Indexed and stored in the tool | Purchase price and address |
| Take-offs and unit costs | Measured by a person, priced from records or documented sources | Derived from property type and size |
| Legal analysis for each classification | Written by a person; the tool tracks it | A class assigned by category |
| Asset list and reconciliation | Produced from the work | Produced arithmetically from the percentage |
| Workpapers for an examination | Exist | A questionnaire and an output |
The left column is what the guide describes. The right column is what an examiner would find when asking for the study, the workpapers, the construction documents and the preparer's qualifications.
How to tell which kind you are looking at
Ask the vendor six questions.
- Who prepares and signs the study? A name with credentials and experience, as the guide expects, or a company name.
- Does anyone visit the property or review drawings and records? If the answer is that the model does not need them, the product is a percentage.
- Where do the component costs come from? Take-offs and documented unit costs, or property-type averages.
- Is there a legal analysis for each classification? Ask to see one for a specific item.
- What do I receive if the return is examined? Workpapers and a person, or the same output again.
- What happens to my documents? Tax return information is protected; disclosure or use without consent is restricted. Read the terms for retention and training on your data before uploading a closing statement.
A vendor who answers all six plainly may be selling a tool with a practitioner behind it, sometimes at a lower price than a traditional engagement because the tool saves time. A vendor who answers with "AI-powered" and "IRS-compliant" is selling the second kind.
What DIY can reasonably do
An owner with time and care can do real work before or instead of paying anyone, and a good tool helps:
- Assemble the file: closing statement, appraisal, drawings, invoices, permits, prior schedules.
- Establish the land split by fair market value with the appraisal or the assessor's ratio, documented.
- Inventory the property: appliances, flooring, window coverings, fencing, paving, equipment, with photographs and invoices.
- Separate later purchases with their own invoices and dates.
That work makes a practitioner's study cheaper and better, and for a small property with little to reclassify it may be the sensible stopping point after a conversation with the adviser. What it does not produce is the classification judgement and the cost support for components inside the purchase price, which is where the study's value and its risk both sit.
What a good tool looks like
A tool worth using makes the practitioner's evidence better and easier to produce. It stores the document index with the request log; it keeps photographs keyed to the asset list; it measures quantities from drawings and records the measurement; it holds unit costs with their source and date and flags a cost applied to the wrong year or region; it separates actual from estimated costs; it carries the classification reason with each asset; and it reconciles to basis on demand and shows the difference when it does not tie. Its report is generated from that work, not in place of it. A tool that does all of this and still leaves the site visit, the classification decision and the signature to a person is a tool; one that offers to skip those steps is a product.
Pricing signals
Price alone does not identify the kind. A practitioner using a good tool on a simple property may charge less than a traditional engagement because the housekeeping is faster. A product may charge more than its work justifies because the buyer cannot see what was skipped. The signal is what the fee buys: an identified preparer, a site record, take-offs, a legal analysis, a reconciliation and workpapers, or an address and a percentage.
Where the risk lands
A questionnaire product is cheap because its output is not evidence. If the return is examined, the examiner asks for the study, the workpapers, the construction documents and the preparer's qualifications. The owner produces a questionnaire. The adviser who signed the return is answerable for it under the professional rules of competence and diligence that apply to practitioners before the IRS, and the owner pays the adjustment. The money saved on the product is not the cost; the adjustment and the adviser's time are.
A reasonable middle
Some practitioners offer a scoped service for smaller properties: the owner assembles the file with the tool's help, the practitioner reviews drawings and photographs, decides classifications with a written reason, prices from documented sources, reconciles, and signs. That is a study, done efficiently. The test is the same as always: does the file contain the elements the guide lists, and does a person with expertise stand behind it.
What people ask on Reddit and other forums
"Is the $500 online study legit" is a monthly thread in the "cost segregation reddit" discussions on r/realestateinvesting. The searches that lead people to these threads are usually phrased "cost segregation software", "DIY cost segregation study" and "online cost segregation calculator".
"Can software do a cost seg?" A tool can support a practitioner's study. A questionnaire product cannot inspect, classify or reconcile; it applies a percentage.
"Is it legal to use one?" Yes. The IRS prescribes no qualifications. The question is whether the output survives examination.
"The vendor says it's IRS-compliant." No product, method or provider is approved by the IRS. The guide describes what examiners look for; ask whether the product's output contains it.
"What can I do myself to save money?" Assemble the file, document the land split, inventory the property with invoices and photographs, and give that to a practitioner or your adviser.
Questions people also ask
Can I do my own cost segregation study with software?
You can assemble the file and inventory the property. The classification judgement and the cost support for components inside the purchase price are what a study is, and software that skips them produces a percentage.
Are online cost segregation calculators accurate?
They estimate from property type and size. The IRS guide treats rule-of-thumb approaches as the least reliable; a calculator is a screening tool, not a study.
What does the IRS look for in a study?
An identified, experienced preparer, documentation, site inspection, legal analysis, take-offs and unit costs, an asset list and reconciliation, and the workpapers behind them.
Is it safe to upload my closing statement to a cost seg website?
Tax return information is protected by law. Read the vendor's terms on data retention and use, and ask your adviser before uploading.
Do practitioners use software?
Yes, as tools for measurement, costing, tracking and reporting. The judgement and the responsibility remain the practitioner's.
Sources
- https://www.irs.gov/pub/irs-pdf/p5653.pdf — IRS Publication 5653, Cost Segregation Audit Techniques Guide (Rev. 2-2025): Chapters 3, 4 and 5.
- https://www.law.cornell.edu/uscode/text/26/7216 — 26 U.S.C. §7216(a).
- https://www.irs.gov/pub/irs-pdf/pcir230.pdf — Treasury Department Circular No. 230: §10.22, §10.35.
- https://www.irs.gov/publications/p551 — IRS Publication 551 (Rev. December 2024), Basis of Assets.
Related reading
- Why universal percentages fail in cost segregation
- Who is qualified to perform a cost segregation study?
- Responsible AI use in cost segregation work
- Cost segregation study cost: what drives the fee
- How the IRS examines a cost segregation study
- What Reddit asks about cost segregation, answered with sources
- Find a practitioner in the NBCSS directory