The 30-second answer
Cost segregation companies come in three types: specialty engineering firms, CPA-firm practices, and automated or software-based providers. Specialty firms (CSSI, Engineered Tax Services, Capstan, Bedford, Madison SPECS, Maven, Cost Segregation Guys) run multi-week, often site-visit studies that fit $5M+ commercial and unusual properties. CPA and accounting firms offer studies to their own clients, either with in-house engineering staff or by working with a specialty provider. Automated providers (Cost Seg Smart) deliver the same methodology aligned with IRS guidance in 1–2 business days from $495, which fits residential and small commercial. All reputable companies use the same core methodology; what differs is who does the work, price, and turnaround. For a firm-by-firm ranking by fit, see best cost segregation companies, compared.
Disclosure: Cost Seg Smart operates this page and is one of the firms listed. We describe firms by best-fit segment rather than ranking them; confirm current pricing and scope directly with each vendor.
The three types of cost segregation companies
1. Specialty engineering firms
Companies whose core business is cost segregation and related incentives. A study is usually led by an engineer or construction cost estimator, often with a site visit, and delivered over several weeks. Fees are typically quoted per property. When this type may be a better fit: large or specialty commercial property, ground-up construction, hospitality, manufacturing, or any building where on-site observation materially changes the component schedule.
2. CPA-firm practices
Many accounting firms offer cost segregation to their existing tax clients. Some keep engineers or cost estimators on staff; others coordinate the study with an outside specialty provider and handle the tax filing side themselves. When this type may be a better fit: you want one firm responsible for the study and the return, or your CPA already has a provider relationship they trust. Ask who actually prepares the study, since that answers the Audit Techniques Guide question of who did the work.
3. Automated and software-based providers
Providers that build studies from structured property data rather than a site visit. This group itself splits into self-service DIY tools, software with engineer review, and done-for-you automated studies. Turnaround is days rather than weeks, and fees are a fraction of a specialty engagement. When this type may be a better fit: residential rentals, short-term rentals, small multifamily, and small commercial property, where the components that drive the result are visible in public records and owner photos. The tools in this group are compared side by side in cost segregation software compared.
Examples: the major cost segregation companies
| Company | Model | Best fit |
|---|---|---|
| Cost Seg Smart | Automated, remote, from $495, within 1–2 business days | Residential, STR, small MF, small commercial |
| CSSI | National rep network, since 2003; turnaround not published | Commercial; local-rep relationship |
| Engineered Tax Services | Full-service specialty tax firm | Commercial; bundles R&D / §179D |
| Cost Segregation Authority | Engineering firm, since 2006 | Commercial; bundles energy incentives |
| Maven | In-house engineer + CPA, condensed or on-site | Owners wanting a named engineer + CPA |
| Cost Segregation Guys | Flat-fee engineering, accountant-coordinated | Commercial; flat-fee preference |
| Madison SPECS | Specialty engineering firm | High-end commercial / industrial |
How to pick a cost segregation company
Every reputable firm uses construction-cost-data component pricing and MACRS classification per Rev. Proc. 87-56, documented to the IRS Audit Techniques Guide. That is table stakes, not a differentiator. Decide on fit: match the firm's price and turnaround to your property. A $5,000 engineering fee is trivial on a $5M building and ruinous on a $400K rental. For the deeper firm-by-firm breakdown, see the best cost segregation companies guide; for individual head-to-heads, the cost segregation comparison hub.