There are a lot of cost segregation providers. They all promise "IRS-compliant reports" and "accelerated depreciation," and they all charge somewhere between $500 and $15,000 for it. Under the marketing, though, the deliverables vary enormously — in depth, in defensibility, in turnaround, and in what you actually get when something goes wrong.
This guide gives you a practical framework for comparing providers on the things that matter. Use it to evaluate any provider, not just us.
1. Is it a real engineering-based study?
This is the single most important question, and the hardest for an owner to evaluate. Here's how to tell:
- Look for property-specific inputs. A real study uses your actual property — photos, square footage, year built, floor plan, site conditions, features, finishes. A weak study uses ZIP-code averages and applies them to a generic property type.
- Ask about the classification method. Real engineering-based studies use the Residual Estimation Method or similar documented approaches. If the provider can't explain their methodology in two sentences, that's a red flag.
- Check whether the report cites your actual features. A quality report will reference your specific flooring, fixtures, cabinetry, site improvements, etc. A generic report will describe a typical rental property that could be yours or any other.
"Engineering-based" is the operative phrase in IRS guidance. A study that doesn't meet that standard is much weaker at audit.
2. What's in the report package?
A complete, defensible cost segregation report should include:
- Executive summary — High-level findings, first-year impact, methodology reference
- Reclassified asset schedules — Every component broken out by 5-, 7-, 15-, and 27.5-year recovery period with its allocated basis
- Full depreciation schedule — Year-by-year deduction projection across all recovery periods
- Photo documentation — Visual evidence supporting the classifications, ideally annotated
- Methodology notes — The specific approach used, with IRS references
- Bonus depreciation applicability analysis — How bonus depreciation applies to the short-life components based on acquisition and placed-in-service dates
- Form 4562 / Form 3115 supporting detail — The specific numbers your CPA will put on your return
If any of those are missing, ask why. Especially the photo documentation and methodology notes — those are what matter in an audit.
3. How defensible is it in an audit?
A well-documented report defends itself; a thin report doesn't. Things to look for:
- Explicit methodology section. The report should name the method and tie it to IRS guidance. "Engineering-based cost segregation study consistent with the IRS Cost Segregation Audit Techniques Guide" is the baseline.
- Property-specific evidence for each short-life classification. If the 15-year property category is $16,000, the report should show which site improvements add up to that number, not just state it.
- Consistent internal logic. The executive summary, asset schedules, and depreciation tables should all match. Reports assembled from templates sometimes have internal inconsistencies that fall apart on inspection.
- Photo support. Every major classification category should have photos that visibly support it.
4. What does "audit support" actually cover?
Every provider promises audit support. Very few define it. Ask specifically:
- What happens if the IRS sends a letter about the study? Does the provider respond? Through whom? Is it included or extra?
- Is there an hours cap? Some providers cap audit support at 1 or 2 hours. Others include unlimited response for methodology questions.
- Does audit support include only defending the methodology, or also preparing documentation? There's a difference.
- Is audit support included in the flat fee or sold separately?
Pinning this down matters. "Audit support included" with no detail is marketing language; "we respond on methodology and documentation at no additional cost" is an actual commitment.
5. Turnaround time
This matters more than people expect. Traditional engineering firms often take 4–8 weeks, which is fine for planning but often useless for tight filing windows. A 2-business-day turnaround means you can start a study in mid-March and still have the report in your CPA's hands for an April 15 filing.
Fast turnaround shouldn't come at the expense of quality — a quality review before delivery is non-negotiable — but for residential rentals, a fully remote, standardized workflow can deliver both.
6. Pricing model
Look for:
- Flat fee vs. hourly. Hourly billing on a cost segregation study almost always ends badly.
- Fee as a percentage of savings (avoid). Some providers charge a percentage of the first-year tax benefit. The IRS has specifically warned against contingent-fee cost segregation arrangements because they create incentive problems for the engineer.
- Additional fees. Any additional fees beyond the base should be disclosed upfront. Bonus depreciation analysis, Form 3115 support, and audit support should all be included in the base fee for residential studies.
7. Property type fit
Not every provider is built for every property. Firms that specialize in commercial real estate often have heavyweight processes that don't pencil out on a $300,000 single-family rental. Residential-specialized providers won't be the right fit for a 200-unit apartment complex.
For residential rentals up to 4 units — single-family, duplex/triplex/fourplex, short-term rentals, and manufactured housing — you want a provider that has built their process specifically for residential. That means standardized methodology, remote-friendly workflow, and pricing that makes sense at residential scales.
A quick checklist
Before committing to a provider, confirm:
- ☐ Engineering-based methodology, not ZIP-code averages
- ☐ Reclassified asset schedules with property-specific support
- ☐ Photo documentation included
- ☐ Methodology notes tied to IRS guidance
- ☐ Bonus depreciation applicability included
- ☐ Form 4562 / Form 3115 supporting detail included
- ☐ Audit support defined, in writing, and included in the flat fee
- ☐ Turnaround time that fits your filing window
- ☐ Flat fee, not contingent on your savings
- ☐ Provider is experienced with your property type
If a provider hits all ten, the report will almost certainly serve you well. If they miss several, keep looking.
How RentalWriteOff measures up
For transparency, here's how we stack up against this checklist:
- Engineering-based methodology: Yes, Residual Estimation Method with property-specific inputs.
- Asset schedules with support: Every classification tied to observed components.
- Photo documentation: Included and annotated in every report.
- Methodology notes: Documented and tied to IRS guidance.
- Bonus depreciation analysis: Included.
- Form 4562 / Form 3115 detail: Included.
- Audit support: Included in the flat fee. We respond to IRS and state inquiries about methodology and documentation at no extra cost.
- Turnaround: 2 business days.
- Flat fee: Yes, no percentage-of-savings pricing.
- Property type fit: Residential rentals up to 4 units, including STRs and manufactured housing. That's what we're built for.
You don't have to take our word for it — run the checklist against any provider you're evaluating. If you want to see what our reports look like on a specific property, use the free calculator or start a study.