Bonus depreciation and Section 179 both let you deduct the cost of an asset in the year you place it in service instead of spreading it across decades. If you own rental or commercial real estate, the choice between them decides how much of a new purchase, renovation, or cost segregation result reaches this year’s return.
As co-founder of Seneca Cost Segregation and a real estate investor myself, I’ve watched plenty of finished studies reach a CPA’s desk with one open question attached: bonus, Section 179, or both? What we see consistently is that the comparison guides owners find were written for equipment buyers, so the real estate rules that change the answer never come up.
Below, I compare the two provisions on limits, eligible assets, and income rules, show where each fits the components a study identifies, and flag the traps that catch landlords most often.
TL;DR — Bonus Depreciation vs Section 179
- ●Bonus has no dollar cap: qualified property acquired and placed in service after January 19, 2025 gets a 100% first-year write-off, however large the purchase.
- ●Section 179 tops out at $2,560,000 for 2026: the cap shrinks dollar for dollar once you place more than $4,090,000 of Section 179 property in service.
- ●Only bonus can push you into a loss: Section 179 stops at your active business income, while bonus can create a loss, subject to the passive and excess business loss rules.
- ●Parking lots and fencing go to bonus: 15-year land improvements a study identifies qualify for bonus and are shut out of Section 179.
- ●A new roof or HVAC system is where Section 179 earns its keep: on a nonresidential building those 39-year systems sit outside bonus, yet an eligible owner can expense them under Section 179.
- ●Most rental investors default to bonus: rentals that are not a trade or business, and noncorporate landlords leasing property out, generally cannot use Section 179 at all.
What Bonus Depreciation and Section 179 Each Do
Both accelerate depreciation by different routes.
How Bonus Depreciation Works Under Current Law
Bonus depreciation is an additional first-year allowance on qualified property, which covers MACRS property with a recovery period of 20 years or less. Under the One Big Beautiful Bill, property acquired and placed in service after January 19, 2025 qualifies for a permanent 100% rate, and “acquired” means the date of the binding written contract.
The allowance applies automatically. If you do not want it, you elect out for an entire class of property placed in service that year, such as all 5-year assets. Our breakdown of the bonus depreciation changes in the Big Beautiful Bill covers the transition dates in more detail.
How the Section 179 Election Works
Section 179 is something you opt into, asset by asset, on Form 4562. For tax years beginning in 2026, the IRS inflation adjustments in Revenue Procedure 2025-32 set the maximum at $2,560,000, reduced by every dollar of Section 179 property placed in service above $4,090,000.
The second limit matters more for most owners. Under IRS Publication 946, the deduction cannot exceed your taxable income from the active conduct of a trade or business, and anything disallowed carries forward to the next year. Partnerships and S corporations face the limits twice, once at the entity and again on each owner’s return.
Bonus Depreciation vs Section 179 Side by Side
Here is how they compare where real estate cases are decided.
Which Real Estate Assets Qualify for Each
A cost segregation study splits a building into components with different recovery periods, and each group lines up with these provisions in its own way.
Short-Life Components From a Cost Segregation Study
The 5- and 7-year property a study identifies, such as carpeting, cabinetry, appliances, and dedicated electrical, is eligible for bonus depreciation. Section 179 can reach some of the same tangible personal property, yet for a typical rental investor the trade-or-business and income limits keep it out of play.
Our guide to tangible personal property identification shows what engineers look for.
Land Improvements and Site Work
Paved parking, sidewalks, fencing, landscaping, and site drainage usually carry a 15-year life, inside the 20-year cutoff for bonus depreciation.
Publication 946 lists land improvements, including paved parking areas and fences, as property that does not qualify for Section 179, so a study’s 15-year bucket flows to bonus by default.
Roofs, HVAC, and Other Building Systems
A replacement roof or a central HVAC system is a structural component of the building, which generally means a 39-year life on nonresidential property and no bonus depreciation unless the work counts as interior qualified improvement property. Section 179 fills that gap through qualified Section 179 real property: roofs, HVAC, fire protection and alarm systems, and security systems added to a nonresidential building after it was first placed in service, plus qualified improvement property.
Picture a business replacing the roof on its own office building for $200,000. Straight-line over 39 years, the deduction runs about $5,128 a year; with a Section 179 election, the business could deduct the full $200,000 in year one, provided it has at least that much active business income. Interior work follows its own path, which our page on leasehold improvements and bonus depreciation explains.
Where Section 179 Falls Short for Rental Property Owners
Three rules keep Section 179 from most buy-and-hold investors, even for qualifying assets.
- ●Trade or business requirement: Publication 946 excludes property acquired only for the production of income, including rental property when renting is not your trade or business.
- ●Business income limit: a new rental that shows little or no active business income gets little or no current Section 179 deduction, with the rest carried forward.
- ●Noncorporate lessor rule: individuals, partnerships, and LLCs taxed as partnerships generally cannot claim Section 179 on property they lease to others, unless the lease and expense tests in Publication 946 are met.
How to Decide Between Bonus Depreciation and Section 179
A few questions with your CPA usually settle it.
- ●Your active business income this year: if it is modest, bonus depreciation can deliver the full deduction now while Section 179 would push part of it into future years.
- ●Whether you can use a loss: bonus can create a loss, but rental losses are generally passive, and the 2026 excess business loss threshold is $256,000 ($512,000 for joint returns).
- ●The asset type: 15-year land improvements point to bonus, while 39-year roofs and HVAC on nonresidential buildings point to Section 179.
- ●How much control you want: Section 179 lets you pick specific assets and amounts, while bonus runs class by class.
- ●Your state return: California, for example, caps Section 179 at $25,000 with a $200,000 phase-out and does not follow the federal qualified real property expansion, according to the Franchise Tax Board’s Form 3885 instructions.
- ●Your hold period: fast deductions on assets you sell soon can return as ordinary income.
How to Use Bonus Depreciation and Section 179 Together
You can claim both in the same year, and the order is set by the rules.
Apply the Section 179 Election First
Publication 946 reduces an asset’s depreciable basis by any Section 179 deduction before the special allowance is figured. Spend the election where bonus cannot reach, such as a nonresidential roof, and stay within your business income limit.
Run Bonus Depreciation on the Remaining Basis
Bonus then applies to the remaining basis in every class you have not elected out of, which at 100% typically clears the full cost of a study’s 5-, 7-, and 15-year property.
Depreciate the Rest Under MACRS
Remaining basis, including the building shell, stays on its regular 27.5- or 39-year schedule. Say an owner-operator with $180,000 of active business income places a $150,000 roof and $350,000 of study-identified components in service: electing Section 179 on the roof and taking bonus on the components produces a $500,000 first-year deduction, with the limits on losses still applying to the bonus portion.
Mistakes to Avoid With Bonus Depreciation and Section 179
Each is common and avoidable.
- ●Expecting Section 179 to create a loss: the deduction stops at active business income, and the excess carries forward. Model income first and route the rest to bonus.
- ●Claiming Section 179 on land improvements: paving, fencing, and similar site work are excluded, which invites an adjustment on review. Take bonus on those components instead.
- ●Ignoring the noncorporate lessor rule: an LLC leasing a building to a tenant can lose a deduction it assumed it had. Confirm the lessor tests with your CPA first.
- ●Missing the binding contract date: property under a written contract signed on or before January 19, 2025 stays on the older phase-down rates even if it is placed in service later. Pull the contract date before you model the deduction.
- ●Forgetting state add-backs: a decoupled state can shrink a large federal deduction. Run the state return alongside the federal one.
- ●Overlooking the business interest election: a real property trade or business that elects out of the Section 163(j) interest limit cannot take bonus on qualified improvement property. Weigh that before electing.
- ●Ignoring recapture at sale: fast write-offs on personal property can be taxed as ordinary income when you sell. Our explainer on the depreciation recapture tax rate shows how that math works.
Frequently Asked Questions
Below are the questions we hear most from owners comparing the two.
How Seneca Fits Into Your Depreciation Plan
Whichever provision your CPA chooses, the deduction is only as strong as the asset classification beneath it. At Seneca, our in-house engineers break down every component of the property, through an onsite visit or a virtual tour depending on the building, and our Head of Engineering signs off on every study before it reaches your CPA. You work directly with a dedicated Project Manager, our Engineering team, and an Advisor, with real-time updates at each stage.
Audit defense comes with every engagement, backed by 10,200+ properties assessed and zero IRS audits triggered or lost. We also run Qualified Production Property (QPP) studies for owners building under the new Section 168(n) rules. Run your numbers through our cost segregation calculator to see what a study could surface.
Conclusion
Bonus depreciation and Section 179 reach the same goal through different doors. For most real estate investors, bonus does the heavy lifting on the 5-, 7-, and 15-year property a study uncovers, while Section 179 serves owner-operators who need to expense a roof, HVAC system, or other building system bonus cannot touch.
The right mix depends on your income, your entity, your state, and how long you plan to hold. Our longer guide to cost segregation and bonus depreciation is a good next read, and when you want real numbers for your property, a free estimate from our team is the place to start.
