This article is educational only and is not legal or tax advice; confirm how these rules apply to your return, entity, financing, and loss limitations with your tax advisor before filing.
A cost segregation study for a property you bought is built from a short list of core files, typically the closing or settlement statement, construction costs and invoices (or the contractor’s pay applications) for anything built or renovated, a land-value source such as an assessor ratio or appraisal, and, when the property is already on a filed or draft return, the current depreciation schedule. If you are on extension and gathering paperwork before you file, the practical question is whether those documents are strong enough to support a cost segregation study on the return you are about to file.
A cost segregation study changes the depreciation schedule attached to that return by separating building components that may qualify for shorter recovery periods from the building shell, which stays on 27.5-year residential rental or 39-year nonresidential depreciation under §168(c). Because cost segregation accelerates deductions rather than creating new basis, the study is only as strong as the paperwork that ties dollars to assets, recovery periods, and placed-in-service dates.
What documents do you need for a cost segregation study before you file?
The core files typically are the closing or settlement statement, construction costs and invoices or contractor pay applications, a land-value source such as an assessor ratio or appraisal, and the current depreciation schedule when the property is already on a filed or draft return. Together they answer the questions that matter on your return: what was bought, what was built or improved, what basis is depreciable after land is removed, and what depreciation has already been claimed.
- Closing or settlement statement: shows the purchase price, credits, prorations, and transaction costs that your tax advisor may capitalize into basis.
- Construction invoices or pay applications: show the cost detail needed to classify improvements into recovery periods under §168.
- Current depreciation schedule, when the property is already on a filed or draft return: shows the method and recovery period already used on filed or draft returns under §167 and §168.
- Land-value source: supports the split between nondepreciable land and depreciable building or improvement basis under §167 and §168.
The closing or settlement statement is usually the anchor for an acquisition because it shows the purchase price, closing costs, credits, and prorations. If the property was purchased and then renovated, the construction invoices or contractor pay applications become equally important, because they show what was added after closing and whether those costs belong in the building shell, land improvements, or tangible personal property.
When the property is already on a filed or draft return, the depreciation schedule tells the study team what your tax preparer has already claimed. If the building is already being depreciated as 27.5-year residential rental property or 39-year nonresidential real property under §168(c), the cost segregation study has to reconcile its new asset classes to that existing schedule.
The land-value source matters because land is not depreciable under §167 and §168, so the study starts from depreciable building and improvement basis rather than the total purchase price. An assessor ratio or appraisal is the usual reference, and your tax advisor should confirm that the land allocation on the return matches the support in your file.
This list is written for a property you acquired. For a building a general contractor built for you, the contractor’s pay applications and the construction drawings carry more of the load, and that case is covered in the document checklist for a contractor-built project.
ClickDrag Finance’s cost segregation qualifier asks about your situation, the property type, when you acquired the property and its approximate depreciable basis, and, after you enter an email, returns an estimated Year 1 deduction range for most property types and bases.
Why are the closing statement and construction costs the core documents for a small-property cost segregation study?
They are the core because they carry the strongest dollar trail: the closing statement fixes the total acquisition cost, and construction invoices tie dollars to specific components. In a smaller rental, office, retail, or mixed-use building, a cost segregation study often turns on whether the acquisition basis and the improvement basis can be allocated with enough support to identify shorter-life assets under §168.
The closing statement starts the acquisition-basis calculation, but it does not describe the assets inside the building. That is why a cost segregation study built on the methodology in the IRS Cost Segregation Audit Techniques Guide uses the closing statement as the total-cost anchor and then uses plans, photographs, invoices, site information, or estimating references to classify components.
Construction costs are more direct when you built, expanded, or renovated the property. If an invoice names flooring, appliances, specialty electrical, cabinetry, exterior paving, fencing, or landscaping, the cost segregation study can often connect those dollars to asset classes more directly than it can from a purchase contract alone.
If your file has only a closing statement and no construction detail, cost segregation may still be possible for an acquired property, but the result depends more heavily on cost estimates, property condition, photographs, and the purchase allocation your tax advisor accepts. If your file has detailed invoices or pay applications, the study can usually rely less on broad estimates because the costs are already separated by trade, draw, or vendor.
Can you still order a cost segregation study before the October 15 extended deadline if you are on extension and have not yet filed?
Yes, if the return is on extension and not yet filed and the study is complete before that return is filed: if you filed Form 4868 and have not yet filed your 2025 Form 1040, October 15, 2026 is the extended due date for that individual return. If you are on extension and have not yet filed, October 15, 2026 is a filing deadline under Form 4868, not a rule that makes an unfinished study usable after the return has been submitted.
If the property owner is a calendar-year C corporation that filed Form 7004 and has not yet filed, October 15, 2026 is also the extended due date for that Form 1120 under Form 7004. For a partnership return on Form 1065 or an S corporation return on Form 1120-S, the extended due date was September 15, 2026 under Form 7004, so an owner who holds the building through one of those entities cannot treat the individual deadline as the entity’s deadline.
How long a study takes depends on the property and on how complete the documents are, so the document review comes before the filing decision. Where the Form 3115 conditions described below are met, filing without the study does not lose the depreciation, because Form 3115 with a later return remains available for a property you placed in service in an earlier tax year and still own.
If you are comparing providers before filing, our guide to the best cost segregation companies explains what to look for in methodology, intake, and review process. If the property is in an Opportunity Zone or held through a Qualified Opportunity Fund, depreciation and basis add another layer, covered in our Opportunity Zone cost segregation guide.
Which documents show whether 100% bonus depreciation applies to the property a cost segregation study reclassifies?
The purchase contract and its amendments show it, not the closing statement alone: under §168(k), as amended by OBBBA in 2025, bonus depreciation is 100% for qualified property acquired after January 19, 2025. Per IRS Notice 2026-11 the acquired-date test turns on the written binding contract, not the closing date: the acquired date is the latest of the date the contract was signed, the date it became enforceable under state law, the end of any cancellation period, and the date any contingency was satisfied (Treas. Reg. §1.168(k)-2(b)(5)(ii)(B)). This applies to a written binding contract, meaning one enforceable under state law that does not limit damages to a specified amount (for example through a liquidated damages clause); under a contract that is not binding in that sense, the acquired date is generally when the taxpayer has paid or incurred more than 10 percent of the total cost, excluding land and preliminary activities (Treas. Reg. §1.168(k)-2(b)(5)(iii) and (v)).
For a 2025 purchase, that makes the signed contract, its amendments, and the records that show when a cancellation period ended or a financing or due-diligence contingency was satisfied part of the document set. Self-constructed property, including property built for the taxpayer under a written binding contract entered into before construction began, is acquired when physical work of a significant nature begins; paying or incurring more than 10 percent of the total cost (excluding land and preliminary activities) is a safe harbor. For a building you built, the records that date the start of physical work therefore matter in the same way.
If the property was acquired on or before January 19, 2025 and placed in service in 2025, the TCJA phase-down applies and bonus depreciation is 40% for 2025 under §168(k). Bonus depreciation under §168(k) applies only to qualified property with a recovery period of 20 years or less, such as the 5-year, 7-year, and 15-year property a cost segregation study identifies, and it does not apply to land or to the 27.5-year residential rental or 39-year nonresidential building shell under §168(c).
On the return you have not filed, the cost segregation study produces a new depreciation schedule showing the building shell, land improvements, and personal-property components separately.
When do the documents show that cost segregation may not help this return?
Cost segregation may not help this return when the documents show a deduction the owner cannot use this year, a short expected hold, or a depreciable basis too small to clear the study fee. A study is generally worth considering only when all three conditions hold: the owner can use the deduction this year under §469, the hold is long enough that §1245 recapture on sale does not erase the timing benefit, and the depreciable basis excluding land clears the study fee, where the roughly $500K floor is a screening guideline rather than a tax rule and moves down as the fee does.
The passive-loss records matter as much as the property documents when the building is a rental. Under §469(c)(2) a rental activity is passive unless an exception applies. Under §469(i), an individual who actively participates in a rental real estate activity (a separate test from material participation, and one that requires an interest of at least 10% by value (a spouse’s interest counts) throughout the year) is exempt from the §469(a) disallowance for up to $25,000 of loss from the rental real estate activities in which the individual actively participates; the $25,000 is reduced by 50% of modified adjusted gross income above $100,000 and is gone at $150,000, and for a married individual filing separately it is $12,500, phasing out between $50,000 and $75,000, only if the spouses lived apart for the entire year, and zero if they lived together at any time during the year. The exceptions, and what happens to a loss that is carried forward, are covered in Will Cost Segregation Help If My Rental or Short-Term Rental Loss Is Passive?
If §469 limits the loss this year, cost segregation still accelerates the depreciation, but the unused passive loss is disallowed under §469(a) and carried forward under §469(b), which is not a current-year tax benefit.
If cost segregation moves basis into §1245 property and the property is later sold at a gain, §1245 treats the depreciation taken on that property as ordinary income up to the gain recognized on it (the lesser of the depreciation taken or the gain), while §1250 continues to govern the building shell.
Which documents does a Form 3115 catch-up need when the property was placed in service in an earlier year?
A Form 3115 catch-up for a property you placed in service in an earlier tax year uses the same core files, and the depreciation schedule becomes essential, because the §481(a) adjustment is the difference between the depreciation already claimed and the depreciation that would have been claimed under the corrected classes. Form 3115 reports missed depreciation on the current return as a §481(a) adjustment, with no amended returns, when the property has been depreciated under the old method on two or more filed returns and the taxpayer still owned it at the start of the year of change. For property the taxpayer placed in service in the tax year immediately before the year of change, with one filed return, either Form 3115 with the current return or an amended return for that year, filed before the return for the following year (the year of change) is filed, is available. A property placed in service in the current year goes on the original return and needs no Form 3115. (Section 6.01 of Rev. Proc. 2025-23, filed under the procedures of Rev. Proc. 2015-13; eligibility rules apply.)
On a 2025 return that is on extension and not yet filed, a building placed in service in 2025 goes on that return and needs no Form 3115. A building placed in service in 2024 or earlier can use Form 3115 with the 2025 return when it has been depreciated on two or more filed returns, or on one filed return if the taxpayer placed it in service in 2024, and the taxpayer still owned it at the start of 2025 and meets the other eligibility rules (for a 2024 building, an amended 2024 return filed before the 2025 return is the alternative).
The route is explained in Form 3115 Cost Segregation Catch-Up Depreciation for a 2025 Return on Extension. For the decision in front of you, the order is simple: if the return that will use the study is not yet filed, the document review comes first; if it is already filed, your tax advisor confirms whether the Form 3115 conditions are met and whether Form 3115 with a later return or an amended return is the route.
Related reading: Can You Still Claim Cost Segregation and Depreciation Before Filing Your 2025 Extended Return?, Cost Segregation and the January 19, 2025 Written-Binding-Contract Cutoff Under IRS Notice 2026-11 and Is Cost Segregation Worth It for a Small Rental Property Under $2 Million?.
Frequently Asked Questions
What documents are required for a cost segregation study?
For a property you acquired, the core files typically are the closing or settlement statement, construction invoices or contractor pay applications, a land-value source such as an assessor ratio or appraisal, and the current depreciation schedule when the property is already on a filed or draft return. Those documents let the study connect depreciable basis under §167 and §168 to the actual property components and remove nondepreciable land from the calculation.
Can I use cost segregation if I only have a closing statement?
Yes, cost segregation may still be possible for an acquired property when the closing statement is the only cost record, but the study then relies more on property facts, photographs, plans, and cost references. If you have invoices or pay applications, those records usually give stronger support for classifying improvement costs under §168.
Does cost segregation increase my total depreciation?
No, cost segregation does not increase total depreciation over the life of the property. It accelerates depreciation by moving qualifying components into shorter recovery periods under §168, the same depreciable basis is recovered over time, and §1245 recapture can apply to the depreciation taken on reclassified personal property when the property is sold at a gain.
Do I need a depreciation schedule before ordering a cost segregation study?
Yes, when the property is already on a filed or draft return, the study uses the depreciation schedule to see what has been claimed under §167 and §168. A property with no prior return, such as one placed in service in 2025 whose 2025 return is on extension and not yet filed, has no schedule to reconcile, and the study’s classes go on that original return.
Which documents show whether bonus depreciation applies to the assets found by cost segregation?
The purchase contract and the placed-in-service records show it, because under §168(k) as amended by OBBBA in 2025, bonus depreciation is 100% for qualified property acquired after January 19, 2025, and bonus depreciation applies only to property with a recovery period of 20 years or less. Per IRS Notice 2026-11, property bought under a written binding contract is acquired on the latest of the date the contract was signed, the date it became enforceable under state law, the end of any cancellation period, and the date any contingency was satisfied (Treas. Reg. §1.168(k)-2(b)(5)(ii)(B)), and property acquired on or before January 19, 2025 and placed in service in 2025 is at 40% under the TCJA phase-down.