A U.S. rental building is normally depreciated over 27.5 years (residential) or 39 years (nonresidential). A cost segregation study breaks the building into its components and reclassifies part of the cost into 5-, 7-, and 15-year property, pulling deductions forward by decades. The permanent return of 100% bonus depreciation under the 2025 tax law (the OBBBA) has made the technique more powerful than ever. This article explains how cost segregation works, when it pays for itself, what happens at sale, and the special issues facing owners who live in Japan. Figures are as of 2026.
What a Cost Segregation Study Does
An engineering-based study allocates the purchase price of a building among its components and assigns each to the correct tax class. The structure itself (foundation, framing, roof, and so on) stays at 27.5 or 39 years, but many components qualify for shorter lives:
- 5-year property: carpeting and removable flooring, appliances, decorative lighting, and certain electrical and plumbing serving specific equipment
- 7-year property: furniture, fixtures, and equipment
- 15-year land improvements: parking lots, sidewalks, fencing, landscaping, and exterior lighting
Depending on the property type, roughly 20% to 40% of the depreciable basis is commonly reclassified, although the actual percentage varies widely. The IRS publishes a Cost Segregation Audit Techniques Guide, and a well-documented study is the expected support for the allocation.
Permanent 100% Bonus Depreciation Raises the Stakes
The One Big Beautiful Bill Act, signed July 4, 2025, permanently restored 100% bonus depreciation for qualified property acquired and placed in service after January 19, 2025. Bonus depreciation applies to property with a recovery period of 20 years or less, which means every dollar moved into the 5-, 7-, and 15-year classes can be deducted in the first year. For a residential property with a $1,000,000 depreciable basis (excluding land) and $250,000 reclassified, straight-line depreciation over 27.5 years would produce roughly $36,000 in the first year; cost segregation plus bonus depreciation produces a first-year deduction well above $250,000.
Look-back studies for property bought in earlier years
A study can be performed on property placed in service in prior years without amending those returns. The owner files Form 3115 to change the accounting method, an automatic change, and takes the cumulative difference in depreciation as a Section 481(a) catch-up deduction in the current year.
Costs and Cautions
- Study fees typically run from a few thousand dollars into the low five figures depending on the property. For small properties, the tax savings may not justify the cost.
- Using the losses: depreciation-driven losses are generally passive under the passive activity loss rules and cannot offset wages. Exceptions apply to real estate professionals (more than 750 hours and more than half of working time in real property trades) and to short-term rentals with average stays of seven days or less where the owner materially participates.
- Recapture at sale: depreciation on Section 1245 components is recaptured as ordinary income, and depreciation on the building is taxed as unrecaptured Section 1250 gain at a maximum 25% rate. Bonus depreciation defers tax; it does not eliminate it.
- State conformity: New York, California, and several other states do not follow federal bonus depreciation, so a separate state depreciation schedule is needed.
Special Issues for Owners Living in Japan
Without the net election, depreciation does nothing
A nonresident alien’s U.S. rental income is taxed by default through 30% withholding on gross rent, with no deductions. To benefit from cost segregation at all, the owner must make the Section 871(d) net election and report net rental income on Form 1040-NR.
Japan will not accept the U.S. depreciation figures
A Japan resident must also report the U.S. rental income in Japan and recompute depreciation under Japanese rules (statutory useful lives and the simplified method for used assets). Cost segregation and bonus depreciation cannot be imported into the Japanese return. In addition, since the 2021 tax year Japan disallows the offsetting of losses from overseas used buildings that arise from depreciation computed under the simplified method against other income. Because taxable income diverges sharply between the two countries, the foreign tax credit limitation is also affected.
Plan for FIRPTA and recapture at exit
When a nonresident sells U.S. real estate, 15% of the gross sale price is withheld under FIRPTA. The accelerated depreciation is recaptured in the U.S. at sale, and Japan separately taxes the gain under its own computation. A large first-year deduction can be largely reversed if the property is sold within a few years, so the holding period should be part of the plan from the start.
Frequently Asked Questions
Is cost segregation worthwhile for a single condominium unit?
Compare the study fee with the tax actually saved. For properties in the low hundreds of thousands of dollars, a streamlined study may be appropriate, or the analysis may show that skipping the study is the better choice. Whether you can use the loss in the current year, given the passive activity rules, is a key part of the decision.
Can I opt out of bonus depreciation?
Yes. You can elect out of bonus depreciation by asset class for the year the property is placed in service. If you expect higher tax rates later or cannot use the loss now, the regular depreciation schedule may be preferable.
Does a 1031 exchange defer the recapture too?
A qualifying like-kind exchange can defer the gain, including recapture on Section 1245 components, but the treatment depends on the mix of assets exchanged and received. Nonresident sellers must also coordinate the FIRPTA withholding certificate, so structure the transaction with an adviser in advance.
This article is provided for general informational purposes only and does not constitute individual tax advice. Please review current IRS rules and Japanese tax law, and consult qualified tax professionals in both countries before acting.
Summary
Cost segregation reclassifies part of a building into short-lived property, and with permanent 100% bonus depreciation it can generate very large first-year deductions. Its real value depends on whether you can use the losses, when you intend to sell, and how state and Japanese rules treat the same property. For owners in Japan, the net election, the limits on depreciation in the Japanese return, and the FIRPTA and recapture consequences at exit all need to be evaluated together before commissioning a study.
Related Articles
- US Real Estate Investment and Depreciation: Maximizing Tax Savings
- Rental Real Estate Depreciation and Recapture: A Comprehensive Guide to Unrecaptured Section 1250 Gain
- US Real Estate Investing While Living in Japan: Form 1040NR and the Net Election Under Section 871(d)
- Navigating Real Estate Rental Losses: A Comparative Analysis of Passive Activity Loss (PAL) Rules in Japan vs. the U.S.