Tax Law
Bonus Depreciation for Real Estate, and How Section 179 Fits In
Cost segregation identifies which parts of your building qualify for a shorter depreciation life. Bonus depreciation and Section 179 are the two tools that determine how much of that reclassified amount you can actually deduct in year one. They work very differently, and for most rental property owners, only one of them usually applies.
What Bonus Depreciation Actually Does
Bonus depreciation lets you deduct a large percentage of a qualifying asset's cost in the year you place it in service, instead of spreading that deduction out over the asset's normal depreciation schedule. It doesn't apply to the building structure itself. It applies to the shorter-life components, typically 5, 7, and 15-year property, that a cost segregation study identifies inside that building. That's exactly why bonus depreciation and cost segregation are so often discussed together: cost segregation finds the components that qualify, and bonus depreciation determines how fast you can deduct them.
The 2025 Change That Made Bonus Depreciation Real Estate's Biggest Lever
Bonus depreciation has existed in some form for years, but it used to be scheduled to phase down gradually toward zero. That changed with the One Big Beautiful Bill Act (OBBBA), which permanently restored 100% bonus depreciation for qualifying property acquired after January 19, 2025. There is no scheduled phase-down written into current law and no annual dollar cap on the amount of bonus depreciation you can claim.
For a property with a large depreciable basis, this means every 5, 7, and 15-year component a cost segregation study identifies can potentially be fully deducted in the very first year of ownership, rather than trickling out over its shorter life. That's a materially different result than the depreciation environment real estate owners were working with just a few years ago.
One nuance worth knowing: the property has to be both acquired and placed in service after that January 19, 2025 date to qualify for the full 100% rate under this permanent restoration. A specialist or your CPA can confirm exactly how your specific acquisition date and timeline line up.
Where Section 179 Fits In
Section 179 is the other accelerated-deduction tool in the tax code, and it also saw its cap raised under the same law, up to $2.5 million. On paper, Section 179 sounds similar to bonus depreciation: both let you deduct a large amount of qualifying property cost immediately instead of over years. In practice, Section 179 comes with two restrictions that make it far less useful for a typical rental property owner.
- Section 179 generally can't create a loss. Your deduction is capped at your business's taxable income for the year, and any excess simply carries forward instead of reducing this year's tax bill. Bonus depreciation has no such limit; it can push a property into a taxable loss.
- Section 179 has stricter active-participation requirements. It's designed around active trades or businesses. Many rental property owners, particularly passive investors, don't meet the bar Section 179 requires, while bonus depreciation carries no comparable active-participation test.
That combination is why bonus depreciation, not Section 179, is usually the tool that actually applies to the components a cost segregation study reclassifies for passive rental owners. Section 179 tends to matter more for owners who also run an active business through the property, such as certain short-term rental operators who materially participate in day-to-day operations.
A Simple Comparison
| Feature | Bonus Depreciation | Section 179 |
|---|---|---|
| Deduction rate (current law) | 100% of qualifying cost | Up to $2.5 million cap |
| Can create a taxable loss | Yes | No, generally capped at taxable income |
| Active-participation requirement | No | Yes, generally requires an active trade or business |
| Typical fit for passive rental owners | Usually applies | Usually doesn't apply |
Federal Law Isn't the Whole Picture
Many states do not fully conform to federal bonus depreciation rules. Some states disallow it entirely for state income tax purposes, others allow a partial amount, and a few follow federal law exactly. That means the impressive federal-level deduction a cost segregation study unlocks can look meaningfully different once your state return is factored in. This is exactly the kind of detail worth modeling with a CPA who knows your specific state's rules before you assume your total tax savings will match the federal number.
Putting It Together
For most rental property owners considering a cost segregation study, the practical takeaway is straightforward: bonus depreciation is almost always the tool that applies to your reclassified components, not Section 179, and under current law it's available at 100% with no phase-down and no dollar cap for qualifying property. What that actually means in dollars depends on your basis, your income, your state, and how long you plan to hold the property. Our Is Cost Segregation Worth It guide walks through exactly how to think through that math, and our full benefits and risks breakdown covers the tradeoffs of accelerating depreciation this aggressively before you commit to a study.
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