Top Cost Segregation Firms For Lookback Studies In 2027

Last updated: November 11, 2026

The best cost segregation firms for lookback studies in 2027 are Engineered Tax Services, KBKG and R.E. Cost Seg, followed by Madison SPECS, CostSegRx and RentalWriteOff. Engineered Tax Services leads for commercial and mixed portfolios, KBKG for owners whose CPA wants a firm with deep depreciation and accounting method experience, and R.E. Cost Seg for investors who want Form 3115 preparation offered alongside the study.

A lookback study is a cost segregation study done on a property you already own. The firm reconstructs the building’s components as of the date you placed it in service, then calculates how much more depreciation you would have claimed. Your CPA usually claims that difference in a single year by filing Form 3115, a change in accounting method, with a Section 481(a) catch-up adjustment. In most cases you do not need to amend prior returns.

That catch-up can be large, which is why lookbacks are one of the most useful tools for investors who skipped cost segregation when they bought. If the mechanics are new to you, read our guide to how cost segregation works first.

Lookback Cost Segregation Firms At A Glance

Firm	Location	Founded	Specialty	Best For
1. Engineered Tax Services	West Palm Beach, FL	2001	Licensed engineering firm for specialty tax	Commercial and mixed portfolios
2. KBKG	Pasadena, CA (seven US offices)	1999	Depreciation, fixed asset and incentive consulting	CPA-led accounting method changes
3. R.E. Cost Seg	Houston, TX	2022	Investor studies with Form 3115 preparation	Investors who want 3115 help bundled
4. Madison SPECS	Lakewood, NJ	2004	Cost segregation only, with in-house engineers	Older multifamily and commercial assets
5. CostSegRx	Sarasota, FL	Not published	Engineer-prepared residential and commercial studies	Rental owners who want 3115 support included
6. RentalWriteOff	Not published	Not published	Flat-fee remote studies for 1 to 4 unit rentals	Small rentals on a fixed budget
7. Cost Seg Smart	Los Angeles, CA	Not published	Fast, low-cost remote studies	Budget lookbacks on residential property
8. Capstan Tax Strategies	Jenkintown, PA	2015	Engineering-driven specialty tax for CRE	Commercial owners with past renovations
9. Kidder Mathews	Seattle, WA	1965	Commercial real estate firm with an engineering cost seg team	West Coast commercial owners
10. Cherry Bekaert	Raleigh, NC	1947	CPA firm pairing licensed engineers with tax staff	Owners who want study and filing in one firm

How We Evaluated These Firms

Every firm on this list performs studies on property already in service. We ranked them on how well they handle the parts that make lookbacks different: calculating the cumulative catch-up, supporting the Form 3115 filing, and documenting a building as it was on its original placed-in-service date, sometimes years after the fact.

We gave extra weight to firms that publish clear lookback guidance, include Form 3115 or Section 481(a) support in their pricing, or show named lookback results. We also considered audit support and price transparency. Rankings are editorial and no firm paid for placement.

Best Cost Segregation Firms For Lookback Studies In 2027

1. Engineered Tax Services — Engineering-Grade Lookbacks For Commercial And Mixed Portfolios

Engineered Tax Services publishes detailed guidance on look-back studies, explaining how a study can be applied retroactively and how Form 3115 lets owners claim previously missed depreciation in the current year. Its message to owners is simple: it is rarely too late, because the catch-up captures all missed depreciation in one adjustment.

As a licensed engineering firm with a national office network, ETS can inspect an older building in person, which matters when the engineer has to reconstruct what was there years ago. It can also review past improvements, which often hold missed depreciation of their own.

Best for: Owners of commercial buildings and mixed portfolios who want an engineering firm to rebuild the asset history behind a large catch-up.

2. KBKG — Depreciation And Accounting Method Depth For CPA-Led Lookbacks

KBKG has worked in cost segregation since 1999 and is known among CPAs for depth on depreciation rules, tangible property regulations and fixed asset reviews. That background is useful on a lookback, where the study has to fit cleanly into a change in accounting method rather than just produce a new asset schedule.

The firm runs seven US offices for engineered studies and also offers self-guided reports through CostSegregation.com for smaller residential properties, so one relationship can cover a large catch-up on a commercial building and a modest one on a rental.

Best for: Owners whose CPA wants a specialist that speaks the language of accounting method changes and fixed asset cleanup.

3. R.E. Cost Seg — Form 3115 Preparation Offered Alongside The Study

R.E. Cost Seg offers Form 3115 preparation as an optional add-on, including the Section 481(a) calculation that shows your cumulative catch-up between the depreciation you took and what the study supports. The firm also publishes plain-language guidance on look-back studies and on when a study is not worth doing.

Studies range from a Rapid Report starting at $950 to a Fully Engineered Study with a virtual or in-person site visit, and every study includes audit support. For investors whose preparer is less comfortable with accounting method changes, having the 3115 work available from the same firm removes a common sticking point.

Best for: Residential and small commercial investors who want the study and the Form 3115 paperwork from one place.

4. Madison SPECS — Large Retro Studies On Long-Held Buildings

Madison SPECS has a published track record on retroactive studies for buildings held for years. In one example, it performed a look-back study on a 154-unit residential development bought in 2006, producing a Section 481(a) adjustment of more than $1 million for the owner.

Its in-house engineers travel to perform site tours, which helps when an older building has been renovated several times and the paper trail is thin. The firm offers a free feasibility analysis, so you can see the likely catch-up before committing.

Best for: Owners of long-held multifamily and commercial buildings with large catch-up potential.

5. CostSegRx — Form 3115 And 481(a) Support In Every Pricing Tier

CostSegRx lists residential studies starting at $895, with custom quotes for multifamily and commercial property. Every pricing tier includes Form 3115 and Section 481(a) support, audit support and report revision support, which is exactly the package a lookback needs.

Studies are completed by its engineers and then reviewed by its accounting team before delivery. That two-step review is reassuring when the study feeds straight into an accounting method change.

Best for: Owners of rentals bought in earlier years who want engineer preparation and catch-up support at a published price.

6. RentalWriteOff — A Flat Fee With Form 3115 Included For Eligible Lookbacks

RentalWriteOff charges an $899 flat fee per property and includes Form 3115 for eligible look-back studies. The process is fully remote, built from appraisal or listing photos, public records and satellite imagery, with delivery in one to two business days after intake.

Audit support comes with every study. For a single-family rental or small multifamily property bought a few years ago, the fixed price makes it easy to judge whether the catch-up is worth pursuing.

Best for: Owners of one to four unit rentals who want a predictable price and the 3115 handled for them.

7. Cost Seg Smart — Lookbacks Priced The Same As A Standard Study

Cost Seg Smart prices lookback studies the same as its standard studies, and it publishes a catch-up calculator so owners can estimate missed depreciation before ordering. The study is performed as if it had been done at purchase, and the report includes the cumulative catch-up amount, component schedules and supporting documentation for the CPA.

Your CPA files the Form 3115 with the current-year return. Studies are remote and delivered quickly, which suits investors working against a filing deadline.

Best for: Residential investors who want a low-cost lookback and already have a CPA ready to file the 3115.

8. Capstan Tax Strategies — Lookbacks Combined With Partial Asset Disposition Work

Capstan Tax Strategies helps CPAs and commercial owners navigate the tangible property and fixed asset regulations, and its studies cover acquisitions, renovations, capital improvements and certain look-back scenarios. Its partners average more than 20 years in the field and have completed more than 8,000 studies.

That regulatory depth matters on older buildings that have been renovated, where a lookback can be paired with partial asset disposition and qualified improvement property analysis to capture value a simple catch-up would miss. Capstan’s engineers are degreed, and the firm offers a warranty for no-cost audit defense.

Best for: Owners of renovated commercial buildings, hotels and retail who want a lookback that also cleans up past improvements.

9. Kidder Mathews — Retroactive Studies Run End To End By Engineers

Kidder Mathews highlights retroactive studies for owners who did not complete cost segregation when they acquired, constructed or renovated a property. Its engineers handle the whole study, including the on-site inspection, which helps on a lookback where someone has to confirm what is actually in the building today.

As a commercial real estate services firm, Kidder Mathews also understands how a building’s history and condition affect value, which helps when reconstructing an asset base from an older purchase.

Best for: Commercial owners, especially in the western US, who want an engineer-led lookback with an in-person inspection.

10. Cherry Bekaert — Study, Accounting Method Change And Return Under One Roof

Cherry Bekaert pairs licensed engineers with tax professionals on every cost segregation study, and because it is also a full CPA firm, it can carry a lookback from the study through the accounting method change and onto the return. Every engagement starts with a complimentary feasibility analysis.

That integration is useful when the catch-up interacts with other parts of your tax picture, such as passive loss limits or a planned sale. The firm is open about the risk of low-cost, software-only studies and builds its work to the standard the IRS expects.

Best for: Owners who want one firm to handle the study, the Form 3115 and the wider tax planning around a large catch-up.

How To Choose A Cost Segregation Firm For A Lookback Study

Who Prepares The Form 3115?

Some firms prepare it, some include support, and some leave it entirely to your CPA. Ask up front, and make sure your preparer is comfortable with accounting method changes before you order the study.

Can The Firm Reconstruct The Original Basis?

A lookback has to describe the building as it was when placed in service, not as it is today. Ask how the firm handles renovations made since purchase and what documents it needs.

Is The Catch-Up Worth It For This Property?

The longer you have owned the building and the higher its basis, the larger the catch-up. If you plan to sell soon, weigh the benefit against depreciation recapture before you commission a study.

Can You Actually Use The Deduction?

A large catch-up only helps if you can use the loss. Passive activity rules can limit it unless you qualify for real estate professional status or the short-term rental exception.

What Audit Support Is Included?

A lookback changes your accounting method, so confirm the firm will defend the study and answer IRS questions for as long as you own the property.

Frequently Asked Questions

What is a cost segregation lookback study?

A lookback study is a cost segregation study done on a property you already own. It recalculates depreciation from the original placed-in-service date and lets you claim the missed amount as a catch-up in the current year.

Do I need to amend my old tax returns?

Usually not. Most lookbacks use Form 3115 to change the accounting method, and the full catch-up is claimed on the current-year return as a Section 481(a) adjustment. Your CPA should confirm the right approach for your situation.

How far back can a lookback study go?

There is no fixed time limit as long as you still own the property and it is still in service. The longer you have held it without a study, the larger the potential catch-up, although the remaining basis shrinks over time.

Do lookback studies cost more than standard studies?

Not always. Several firms on this list price lookbacks the same as a new-purchase study. Others charge extra for Form 3115 preparation. See our guide to cost segregation study pricing.

Conclusion

For most investors, the right lookback firm depends on property size. Engineered Tax Services, KBKG, Madison SPECS and Capstan suit larger and commercial catch-ups, while R.E. Cost Seg, CostSegRx, RentalWriteOff and Cost Seg Smart make small residential lookbacks affordable. Cherry Bekaert and Kidder Mathews are strong when you want an engineer and a CPA working the same file.

For related options, see our lists of cost segregation firms for small residential investors, cost segregation firms that offer on-site property visits and cost segregation firms for single-family rentals.