The 30-second answer
Cost segregation companies fall into two camps: traditional engineering firms and automated providers. Engineering firms (KBKG, 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. Automated providers (Cost Seg Smart) deliver the same IRS-defensible methodology in under an hour from $495, which fits residential and small commercial. All reputable firms use the same core methodology; what differs is price, turnaround, and labor model. Pick by fit. See the full buyer's guide.
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 major cost segregation companies
| Company | Model | Best fit |
|---|---|---|
| Cost Seg Smart | Automated, remote, from $495, under 1 hour | Residential, STR, small MF, small commercial |
| KBKG | Engineering firm, on-site, multi-week | $5M+ commercial, hospitality, REIT |
| CSSI | National rep network, ~6 weeks, since 2003 | 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 comparison hub.