In one paragraph
CSSI and Cost Seg Smart both produce IRS ATG-aligned engineered cost segregation studies using industry-standard construction cost data and MACRS classification per Rev. Proc. 87-56. CSSI (Cost Segregation Services, Inc.) is a long-established national firm working since 2003 through a network of local representatives, with more than 60,000 studies completed, availability in all 50 states, and a typical turnaround around six weeks. Cost Seg Smart's studies are automated and done for you, with internal technical review and QC, delivered in under one hour starting at $495. CSSI may be the better fit for commercial owners who want a local representative relationship and a firm with very long tenure and large study volume. Cost Seg Smart may be the better fit for residential and small-commercial where speed and study cost decide the ROI.
Disclosure: Cost Seg Smart operates this comparison and is one of the firms compared here. See the methodology page for our standalone documentation.
CSSI: overview
CSSI (cssiservices.com) is a national, engineering-based cost segregation firm operating since 2003 with more than 60,000 studies completed and availability in all 50 states through a network of local representatives who coordinate the engagement with the property owner and their CPA. CSSI focuses heavily on commercial property and typically completes studies in about six weeks, and it publicizes a long track record of studies delivered without triggering IRS audits. The methodology and Rev. Proc. 87-56 MACRS framework are the same ones Cost Seg Smart uses; the differences are the labor model, turnaround, and study cost.
At a glance
| Dimension | Cost Seg Smart | CSSI |
|---|---|---|
| Study fee | From $495 | Quoted per property (confirm with vendor) |
| Turnaround | Under 1 hour (simple residential) | ~6 weeks typical |
| Model | Direct, automated, done for you | Local-representative network |
| Track record | Modern automated provider | Since 2003; 60,000+ studies |
| Methodology | industry-standard construction cost data + MACRS per Rev. Proc. 87-56 | engineering-based, construction cost data + MACRS |
| Form 3115 lookback | Included | Supported |
| Best fit | Residential / STR / small MF / small commercial | Commercial owners wanting a local rep + long tenure |
Methodology overlap (both firms)
- Industry-standard construction cost data with regional multipliers.
- MACRS classification per Rev. Proc. 87-56 (IRS Pub. 946 Appendix B).
- IRS Cost Segregation Audit Techniques Guide (Pub 5653) 13-element framework.
- Form 3115 §481(a) lookback for properties owned 2+ years.
- A reviewed, audit-supported deliverable at both firms.
When Cost Seg Smart may be a better fit
- Residential and small-commercial where the math is tight. From $495 and under an hour, the study fee does not eat the Year-1 benefit.
- Speed-sensitive filings. 60-minute turnaround vs. roughly six weeks.
- You prefer a direct, self-serve flow. No local-rep scheduling; order and upload online.
When CSSI may be a better fit
- Commercial property with a local-relationship preference. If you want a representative who meets with you and your CPA, CSSI's network model is built for that.
- You value very long tenure and volume. Two decades of studies and a large completed-study count are reassuring on a six-figure deduction.
- Larger or specialty commercial. CSSI's commercial focus suits bigger or more specialized buildings.
How to decide
- Is this a larger commercial property where you want a local representative relationship? Then CSSI fits well.
- Do you specifically value a firm with two decades of tenure and tens of thousands of studies? Then CSSI.
- Otherwise (residential, STR, small MF, small commercial, speed-sensitive)? Then Cost Seg Smart.
See the math with our free calculator. Methodology at /methodology/; pricing at /cheap-cost-segregation/; the full firm landscape at best cost segregation companies.
Last reviewed: June 2026. Maintained by the Cost Seg Smart Editorial Team. CSSI and Cost Segregation Services, Inc. are trademarks of their respective holder. No affiliation. This comparison is informational; both firms produce IRS ATG-aligned engineered cost segregation studies. Confirm pricing and scope directly with each vendor.