🇺🇸 Made in America·100% U.S.-Based Team · 24+ Years in Cost Segregation
A real estate investor named David sat in his accountant's office in Atlanta last fall holding a Form 3115 in his hand for the first time. He had bought an $8 million office building in 2019. He had owned it for nearly six years without ever doing a cost segregation study. His CPA had set the depreciation at $205,000 per year on a 39-year schedule. David had paid exactly that depreciation amount on every tax return since.
His accountant slid a printout across the desk. The number on it was $1,847,000.
"What is that?" David asked.
"That is the cost segregation catch-up. Six years of accelerated depreciation you should have been claiming all along. The IRS lets you take it all in this year's return."
David did the math in his head. At his marginal tax bracket, $1.8 million in catch-up deductions was roughly $666,000 in actual federal tax savings. In one year. On a study he had not done.
He looked at his accountant. "Why has nobody told me this was an option?"
His accountant did not have a good answer.
Form 3115 is one of the most powerful tools in the cost segregation playbook, and one of the least understood by commercial property owners. It is the IRS-approved mechanism that lets a property owner who never did a cost segregation study, or whose original study was incomplete, claim every missed depreciation deduction in a single tax year. No amended returns. No going back through prior years. One filing. One catch-up. The deduction the law authorized all along, claimed now.
This article walks through how Form 3115 works specifically in the cost segregation context.
Form 3115 is the IRS form for an Application for Change in Accounting Method. It is filed when a taxpayer wants to change how a specific item is treated on the tax return going forward. In the cost segregation context, it applies to depreciation.
When you do a cost segregation study on a property you have owned for several years, you are not amending old returns. You are changing your depreciation method going forward from the current year. The catch-up calculation is called a Section 481(a) adjustment. It captures the difference between the depreciation you actually claimed in prior years and the depreciation you would have claimed if the cost segregation study had been in place at the start.
Here is the math in plain English. If you have owned a property for six years and claimed $205,000 of depreciation per year, you have claimed roughly $1,230,000 in total depreciation. If a cost segregation study shows that you should have been claiming $560,000 per year on average, the depreciation you should have claimed over six years is $3,360,000. The difference is $2,130,000. Form 3115 lets you claim that entire difference in the current tax year as a positive §481(a) adjustment.
In a single filing, $2.1 million of deduction the law always allowed but you never claimed becomes available on the current year's return.
Cost segregation changes are categorized by the IRS as an automatic change in accounting method. This is a critical distinction. Automatic changes do not require IRS pre-approval. The taxpayer files Form 3115 with the current year tax return, applies the §481(a) adjustment, and the change is deemed approved.
The specific designated change number for cost segregation is DCN #7. The procedure is governed by Rev. Proc. 2015-13 and updated periodically through subsequent revenue procedures. The current automatic change procedure was clarified in Rev. Proc. 2024-23. Following DCN #7 correctly is mandatory.
The Cost Seg America team has been performing engineered cost segregation studies that support Form 3115 filings for more than 24 years. The team has guided more than 16,000 of these. The team has defended 125 IRS audits without a single loss. Every Form 3115 filing has been correctly categorized under DCN #7. Every §481(a) adjustment has been calculated from documented engineering analysis rather than estimation.
The lookback window for cost segregation is generous. Under current Treasury rules, a property owner can file Form 3115 to apply cost segregation to a property placed in service in any tax year that remains open under the depreciation rules. Practically, this means roughly 10 years of catch-up depreciation can be captured in the current year's return.
A property purchased in 2016 and never studied can still benefit from a Form 3115 lookback in the current tax year. A property purchased in 2020 can certainly benefit. A property purchased last year can benefit even more, since the full Year 1 deduction is still available.
Run the math on common scenarios:
$2 million property, owned 5 years, never studied. A 30 percent reclassification rate produces roughly $600,000 of accelerated property that should have been deducted earlier than the 39-year schedule. The §481(a) catch-up captures approximately $440,000 of additional Year 1 deduction in the current return. At a 37 percent marginal federal bracket, that is roughly $163,000 in actual federal tax savings claimed this year on a property purchased five years ago.
$5 million property, owned 7 years, never studied. A 30 percent reclassification on $5 million produces $1.5 million of accelerated property. The §481(a) catch-up captures roughly $1.15 million of additional current-year deduction. At a 37 percent bracket, that is $425,500 in actual federal tax savings in a single return.
$10 million property, owned 4 years, never studied. A 30 percent reclassification produces $3 million of accelerated property. The §481(a) catch-up captures approximately $2.3 million of current-year deduction. Federal tax savings at 37 percent: $851,000.
These are not projections of future savings. They are recoveries of deductions that should have been claimed in prior years but were not. The IRS allows the full recovery in one current-year filing.
The Form 3115 is a CPA filing. It accompanies the property owner's tax return. The cost segregation firm provides the engineering documentation and the §481(a) calculation. The CPA files the Form 3115 with the return.
That is the standard division of labor. The cost segregation firm produces the study, including a precise §481(a) calculation supported by component-by-component analysis. The CPA reviews the analysis, completes the Form 3115 itself, and files it as part of the regular tax return work.
If your CPA does not want to handle the Form 3115 filing, the Cost Seg America team can refer the matter to a partner CPA who specializes in cost segregation Form 3115 filings. That partner CPA charges a separate fee for the filing work. This is a backup option, not the default path.
The Form 3115 itself is a relatively short IRS form. The work behind it is substantial.
The engineered cost segregation study. The full report on the property, built to IRS Approaches 1 and 2 standards, with the Project Cost Summary, Component Unit Summary, and Component Unit Detail schedules.
The §481(a) adjustment calculation. A schedule showing the depreciation actually claimed since the property was placed in service, the depreciation that should have been claimed under the cost segregation analysis, and the difference (which is the catch-up adjustment).
The DCN #7 designation. The Form 3115 itself indicates that the change is an automatic change under DCN #7.
Supporting tax-year detail. Year-by-year depreciation schedules showing what was claimed and what should have been claimed.
Signed and dated by the taxpayer and the preparer. The Form 3115 has signature requirements for both.
Filed with the tax return AND with the IRS national office. The Form 3115 for automatic changes is filed in duplicate. One copy goes with the tax return. The other goes directly to the IRS Ogden Service Center under the automatic consent procedures.
Wrong DCN number. Some firms file under DCN #4, DCN #8, or other numbers. Cost segregation changes are DCN #7.
Estimated §481(a) calculation. Some firms produce a Form 3115 §481(a) adjustment that is just an estimate based on category percentages, without supporting component-level documentation. The §481(a) adjustment should be tied to the specific engineering analysis.
Incorrect prior-year depreciation reconciliation. The §481(a) calculation requires an accurate year-by-year reconciliation of what was actually claimed versus what should have been claimed.
Failure to file the duplicate copy with the IRS service center. The automatic change procedure requires the Form 3115 to be filed in duplicate.
No supporting engineering documentation. Form 3115 filings unsupported by an engineered cost segregation study sometimes get challenged on the grounds that the change in depreciation method is not supported by an actual analysis.
Can I file Form 3115 if I have owned the property for more than 10 years? The answer depends on whether the property is still on the depreciation schedule. If the property is in year 12 of a 39-year schedule, yes, you can still file Form 3115 to apply cost segregation. The math gets stronger the longer you have owned the property without a study.
Do I need to amend my prior tax returns to claim cost segregation on an existing property? No. Form 3115 is the IRS-approved alternative to amending prior returns. The §481(a) adjustment claims the entire catch-up in the current tax year as a single positive adjustment to depreciation.
Will filing Form 3115 trigger an IRS audit? Form 3115 filings are routine accounting method changes. A correctly prepared Form 3115 filing supported by an engineered cost segregation study does not flag the return for additional examination scrutiny.
What happens to depreciation going forward after the Form 3115 catch-up? The catch-up captures all the deferred deduction from prior years in the current return. Going forward, the property continues on the new depreciation schedule established by the cost segregation study.
How long does the Form 3115 cost segregation process take? A typical engineered cost segregation study takes 4 to 6 weeks from start to finish. The §481(a) calculation and supporting schedules are built into the study deliverables.
If you own a commercial or rental property that you have held for more than one tax year, and you have never done a cost segregation study, you have unclaimed federal deductions sitting on the table. The Form 3115 lookback is the IRS-approved way to bring those deductions home. In a single tax year. With no amended returns.
The Cost Seg America team has been performing engineered cost segregation studies that support Form 3115 lookback filings for more than 24 years. 16,000 studies. 125 IRS audits defended. Zero losses. $0 ever returned to the IRS. The average first-year savings across the 16,000+ completed studies is $438,511. Every study uses IRS Approaches 1 and 2. Every study is engineered, not estimated. Every Form 3115 package is built to the standards the IRS Audit Technique Guide describes. Unlimited audit defense included on every study. No time limit. No hour cap. No additional fee. Ever. Made in America, by Americans.
The next step on your property takes 30 seconds. Send the property address, the approximate purchase price, and the year you placed it in service. The Cost Seg America team sends back a free preliminary proposal within 24 hours.
Email: info@costsegamerica.com
Phone: 1-888-365-5023
Online: costsegamerica.com/free-proposal
David in Atlanta filed his Form 3115 with his 2024 tax return. The $1,847,000 §481(a) adjustment reduced his federal tax bill by $666,000 in a single filing. Money he had already paid to the IRS in prior years through depreciation he was legally entitled to but had never claimed. The deductions had been sitting there since 2019. They were always his. The Form 3115 just brought them home.
If you own a property and never did a study, your number is sitting there too.
