Cost Segregation Study for Physicians: DIY or Hire a Pro? A Tax Planning Guide
You closed on a rental last spring. A colleague in the physicians’ lounge mentioned “cost seg,” you Googled it, and now you have two quotes on your desk. One is from an engineering firm. The other is from a website that promises a cost segregation study in five minutes, at a small fraction of the engineering quote.
Same words on the invoice. Very different products. This guide covers what a cost segregation study is, what the IRS says about who can prepare one, and what drives the price. Then it gets to the decision: pay for the engineering version, use software, or skip the study because the deduction would be trapped anyway. That last case is the one the vendor pages never mention. Based on current law as of September 18, 2026.
In This Blog
What is a cost segregation study?
A cost segregation study breaks the purchase price of a building into its components. It then assigns each one the recovery period the tax code actually gives that type of property, which is often far shorter than the building’s. Instead of writing off the entire building over 27.5 years (residential rental) or 39 years (nonresidential), the study identifies the pieces that qualify as 5-, 7-, or 15-year property, which can be deducted far faster.
Land never enters the picture. As the IRS puts it in Publication 527, you can’t depreciate the cost of land because land generally doesn’t wear out, become obsolete, or get used up. Every study, DIY or professional, starts by carving the land value out of the price.
What typically gets reclassified into shorter lives, using the IRS’s own examples:
Appliances such as stoves and refrigerators, carpets, and furniture used in the rental, which Publication 527 lists as 5 year property
Wall coverings, partitions, millwork, and lighting fixtures, which the IRS cost segregation guide lists as items that can qualify as section 1245 property, depending on the facts
Roads, fences, and shrubbery, which Publication 527 lists as 15-year property
Qualified improvement property, meaning certain interior improvements to a nonresidential building, which the Form 4562 instructions list as 15 year property
For the full mechanics, start with our guide to how cost segregation works for physicians. This post assumes you want a study and asks how to get one that holds up.
Why does a study matter so much more under current law?
Because of bonus depreciation. The One Big Beautiful Bill Act (OBBBA) restored a 100% first-year deduction for qualified property acquired and placed in service after January 19, 2025, and made it permanent. The IRS confirmed the rule in Notice 2026-11 and the 2025 Form 4562 instructions.
Here is why that changes the math. The 27.5- or 39-year building shell is not eligible for bonus depreciation. The 5-, 7-, and 15 year components a study carves out are. So the share of your basis a study reclassifies is, in most cases, the share you can deduct in year one.
Two cautions apply.
Property acquired before January 20, 2025 and placed in service during 2025 follows the older phase-down and is limited to a 40% bonus allowance. If you bought under the old rules, your tax team will tell you which schedule applies to the year you placed the property in service.
The acquisition date is not always the closing date. Under the new law, property is not treated as acquired after the date a written binding contract is entered into for the purchase. A contract signed on or before January 19, 2025 can put a later closing on the old schedule.
We cover the full schedule in our post on the bonus depreciation schedule under OBBBA.
Can I do my own cost segregation study?
Legally, yes. The IRS does not license cost segregation preparers. Its own Cost Segregation Audit Techniques Guide, the manual its examiners use, states plainly that there are no prescribed qualifications for cost segregation preparers.
Read the next sentence in that guide, though. Preparing a study requires knowledge of both the construction process and the tax law involving property classifications for depreciation purposes. Who signed the report matters less to the IRS than whether the person doing the work understood how buildings are built and how the code classifies each piece.
The guide also ranks the methods a study can use. At the top sits the detailed engineering approach built from actual cost records, which the IRS calls the most methodical and accurate approach. At the bottom sits the “rule of thumb” approach, where the guide tells examiners to view the method with caution since it lacks sufficient documentation to support its allocation of project costs. In between are estimate and sampling methods, and the guide notes the residual estimation method can also be less accurate.
So yes, you can do your own study. The IRS will judge it by the same standard it applies to a full engineering report.
What does DIY software actually produce?
Most “DIY” products are not you with a tape measure. They are software that takes your purchase price, square footage, property type, and photos, then applies modeled allocation percentages to produce a report. Some offer a tier where a tax professional reviews the output.
Ask any DIY provider three questions:
Which of the IRS methodologies does the report use, and does it say so in writing?
Was there a site inspection, or is the allocation modeled from comparable properties?
If the IRS asks, who explains the numbers, and is that included in the price?
The answers tell you whether you bought an engineering study delivered through software, or a percentage applied to your basis.
Do CPAs do cost segregation studies?
Some do. Most tax professionals, including our tax team, do not measure buildings. We apply the study. We decide whether the loss is usable, put the reclassified assets on Form 4562, file Form 3115 for a look-back, and fit the result into the rest of your return. The measuring and costing is engineering work, and the IRS guide lists 13 elements of a quality study that read like an engineering scope.
How much does a cost segregation study cost?
Pricing is set by the provider and moves with the market, so we will not print a range here. What we can tell you is what drives the price and what to compare.
For a professional engineering study, price scales with:
Property type and size (a single-family rental costs less to study than a medical office building)
Whether the engineer visits the site or works from plans and photos
Whether it is a new purchase or a look-back on a property you have owned for years
Whether audit support is included, and for how long
For a software report, you are paying for the model and the report template, plus any professional review tier, plus your own time gathering documents and photos.
The fee itself is generally deductible as an expense of the rental. Publication 527 lists legal and other professional expenses, such as tax return preparation fees, as rental expenses, so the study fee travels with your other rental expenses rather than as a personal deduction. Your tax team will confirm how it is treated on your return, since the answer can depend on your facts.
DIY vs professional: how do you decide?
Here is the comparison the vendor pages will not give you, because each one sells one side of it.
Comparison | Professional engineering study | DIY or software report |
Method | Detailed engineering from actual costs or a detailed cost estimate, the approaches the IRS guide ranks highest | Modeled or statistical allocation; ask which IRS methodology it maps to |
Site inspection | Usually yes | Usually no |
Documentation | Full report: methodology, quantity takeoff, cost reconciliation, asset lists | Summary report; depth varies by product |
Audit support | Typically included or available | Limited or none |
Turnaround | Weeks | Days or minutes |
Price | Higher, quoted per property | Lower, often flat |
Best fit | Higher basis, commercial or mixed-use, furnished STRs, look-back studies, any physician relying on REPS or the STR path to use the loss | Low basis, simple single-family, owner who will still verify land allocation and keep records |
When is a professional study worth it?
The depreciable basis is large enough that a few percentage points of allocation swing tens of thousands of dollars. The bigger the building, the more a defensible allocation is worth.
The property is commercial, mixed-use, or a heavily furnished short-term rental, where the classification questions are harder and more is at stake in each one.
You are doing a look-back study on a property you have owned for several years, where the catch-up deduction is large and the Form 3115 filing must be right.
You are a physician household using Real Estate Professional Status or the short-term rental path to offset income taxed at the top bracket. A large, nonpassive deduction built on an allocation is exactly what the IRS audit guide tells its examiners to scrutinize, and you want the report that answers their questions.
When is DIY or software reasonable?
The basis is modest and the property is a simple single-family rental.
You understand that the report may not include a site inspection or audit support.
You still confirm the land allocation yourself and keep every record.
You have your tax team review the output before it goes on a return.
What goes wrong with DIY?
The failure modes are predictable:
Allocation percentages that are too aggressive for the actual building
Land treated as depreciable, or the land split not documented
Structural components (the roof, load-bearing walls, general electrical) classified as personal property
No documentation that can answer an IRS letter two years later
If an allocation cannot be supported on examination, the tax code provides a 20% accuracy-related penalty on the resulting underpayment under section 6662, in addition to the tax and interest. An understatement is “substantial” once it exceeds the greater of 10% of the tax required to be shown on the return or $5,000, a bar a large depreciation error clears easily.
Nothing in the tax code says DIY studies get examined more often, and we do not sell studies of either kind. The IRS judges the methodology and the documentation, whoever prepared the report.
Is a cost segregation study worth it for a physician? The question most guides skip
Every page that ranks for this topic shows you a big first-year deduction. Not one asks whether you can use it.
Rental real estate is a passive activity by default under section 469. A passive loss offsets passive income, not your W-2 or 1099 clinical income. A study that creates a $130,000 loss you cannot deduct this year has handed you a suspended loss to carry forward. There are three ways out. Two of them work for physicians.
The $25,000 allowance. The code lets active participants deduct up to $25,000 of rental loss against other income. The allowance shrinks by 50% of adjusted gross income over $100,000. Per Publication 925, it is gone once modified adjusted gross income reaches $150,000 ($75,000 if married filing separately). For an attending, this door is closed.
Real Estate Professional Status. You, or your spouse on a joint return, must spend more than 750 hours during the year in real property trades or businesses in which you materially participate. That time must also be more than half of all your working time. A full-time physician rarely clears the second test alone, so REPS is usually reached through a spouse. Our guide to Real Estate Professional Status for physicians walks through the tests and the time logs.
The short-term rental path. Under the passive activity regulations, an activity is not a rental activity if the average period of customer use is seven days or less. The property then falls outside the default rule that rental activity is passive, and if you materially participate, the loss is nonpassive. The most common test is more than 100 hours in the year, with no other individual (cleaner, manager, contractor) participating more than you. Document the hours as you go. Start with our short-term rental tax loophole guide for physicians.
Even a nonpassive loss has a ceiling. For the 2026 tax year, the excess business loss rules cap the net business loss you can use against other income at $256,000, or $512,000 on a joint return, per Rev. Proc. 2025-32. Anything above that is not lost. It carries forward as a net operating loss.
The order of operations, then: confirm the loss is usable this year, then decide how much to spend making it defensible. Paying for an engineering study on a loss that will be suspended is the most expensive way to feel productive.
Worked example: Dr. Okafor’s short-term rental
Dr. Okafor is a hospitalist with W-2 income plus 1099 moonlighting, filing jointly, in the 37% federal bracket (for 2026, taxable income above $768,700 on a joint return). In March 2026 she buys a furnished short-term rental for $600,000, averages three-night stays, and logs the hours to materially participate.
Assumptions, all hypothetical and for illustration only:
Land allocation: $120,000, using the county assessor’s land-to-building ratio, a method Publication 527 accepts when fair market values are uncertain
Depreciable basis: $480,000
Reclassification percentages and study fees below are assumptions, not quotes
Figures for a full year, before the mid-month convention that prorates the building’s first year and before any state tax
No study:
Building basis: $480,000
Straight-line over 27.5 years: about $17,455 of depreciation per year
Deduction in year one: about $17,455
DIY software report (assumes 30% reclassified):
Reclassified to 5-, 7-, and 15-year property: $144,000
100% bonus depreciation on the reclassified components: $144,000
Remaining building basis: $336,000, over 27.5 years: about $12,218
Deduction in year one: about $156,218
Fee: assume $800. Documentation: a modeled report, no site visit
Professional engineering study (site inspection supports 25% reclassified):
Reclassified: $120,000
100% bonus depreciation: $120,000
Remaining building basis: $360,000, over 27.5 years: about $13,091
Deduction in year one: about $133,091
Fee: assume $7,500. Documentation: full report with methodology, asset list, cost reconciliation, and audit support
Read the two study cases carefully. The DIY report produced a bigger number on paper. That gap of five percentage points in allocation is exactly what an examiner tests, and if the 30% cannot be supported, the “savings” reverse with interest and a possible 20% penalty. The engineering study’s smaller number is the one Dr. Okafor can defend.
Because she materially participates in a short-term rental, the loss is nonpassive. The difference between $17,455 and $133,091 is about $115,600 of additional first-year deduction. At a 37% marginal rate, that potentially defers about $42,800 of federal tax into future years. Set that against an assumed $7,500 fee and the deferred tax is many times the cost of the study. The documentation is what she is actually buying.
Her tax team also models two items before she signs the engagement letter. The reclassified components are section 1245 property, so the depreciation she takes on them is recaptured as ordinary income when she sells. And the 3.8% net investment income tax may apply to rental income and to gain at sale, depending on how the activity is classified. The $250,000 joint threshold for that tax is not indexed for inflation.
Already own the property? The look-back study
A study is not just for the year you buy. If you have owned a rental for several years and depreciated the whole building over 27.5 years, a look-back study can reclassify the components now.
Once you have depreciated the property the same way on two or more consecutive returns, the IRS treats that as an adopted method of accounting, per Publication 946. Switching from an impermissible to a permissible depreciation method is then a change in accounting method under the regulations. Rev. Proc. 2025-23 lists it as an automatic change. You file Form 3115 and take a section 481(a) adjustment, the catch-up for depreciation you should have taken. That is a different path from amending a prior return, which the IRS reserves for narrower fixes such as a mathematical error. Under the form instructions, a negative adjustment (one that reduces income) is generally taken into account in the year of change.
This is where a professional study earns its fee. The catch-up on a property held five years can be large, the classification has to be right, and the Form 3115 has to be filed correctly with the return. It is also where a DIY report is hardest to defend, because the examiner is looking at several years of depreciation at once.
What happens when you sell?
Cost segregation pulls deductions forward, and the tax code collects on them later. When you sell, depreciation you claimed on the reclassified 5-, 7-, and 15-year components (section 1245 property) is recaptured as ordinary income. Depreciation on the building shell is unrecaptured section 1250 gain, taxed at up to 25%. A physician who plans to hold for many years, or who expects a lower bracket at sale, may come out ahead. A physician who flips in three years may simply be prepaying a deduction. We go deeper in our post on depreciation recapture at sale and on residential vs commercial vs STR depreciation timelines.
Where your tax team fits in
We do not perform cost segregation studies and we do not recommend a vendor. What your tax team does is the part that decides whether the study was worth buying:
Confirm the loss is usable this year (REPS, the short-term rental path, and the excess business loss cap)
Vet the provider’s methodology against the IRS Audit Techniques Guide before you pay
Apply the study on Form 4562, or file Form 3115 for a look-back
Coordinate the result with your quarterly estimates and your state return, since state rules vary. California, for example, does not allow the federal bonus depreciation deduction, so the state return adds the difference back.
Before you pay for a study, or skip one, talk to your tax team about whether the loss is usable this year. Then buy the level of documentation your numbers require, because a deduction you cannot defend tends to come back as a letter from the IRS.
Contact your tax team today. Prompt, dependable communication throughout the year.
Disclaimer: This material is intended for educational and informational purposes only and does not constitute tax, legal, accounting, or financial advice. The content is general in nature and may not apply to your specific circumstances. Tax laws and financial regulations are subject to change and interpretation, and the application of these laws can vary based on individual situations. Before making any decisions, you should consult with a qualified tax advisor, legal counsel, or financial professional.
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