Real Estate Tax Calc
How they differ
Bonus depreciation applies automatically to qualifying assets with a recovery period of 20 years or less and can create or increase a loss. Section 179 is an election, has an annual dollar cap, and cannot create a loss — it is limited to your business taxable income.
What real estate qualifies
Both can apply to short-life assets identified in a cost segregation study — appliances, carpet, land improvements. Section 179 was expanded to cover certain nonresidential improvements like roofs, HVAC, and security systems, which bonus depreciation may not reach for residential rentals.
Which to use
Many investors use bonus depreciation for the bulk of cost-segregated assets because it can generate a loss, then apply Section 179 selectively to items bonus does not cover. Because Section 179 is income-limited and subject to state conformity differences, model both before filing.
The dollar limits and phase-out for Section 179
Section 179 has a moving annual cap set by statute and indexed for inflation. There is a maximum amount you can expense each year, and once your total qualifying purchases for the year exceed a much higher investment threshold, the deduction phases out dollar-for-dollar. High-volume buyers can lose the Section 179 election entirely in a big purchasing year. Bonus depreciation, by contrast, has no dollar cap and no spending-based phase-out, which is why it does the heavy lifting on large cost-segregation deductions. Always confirm the current-year figures, since Congress and inflation indexing adjust them regularly.
The taxable-income limitation in detail
The single biggest practical difference is the income limit. Section 179 cannot exceed your aggregate business taxable income for the year, and any amount disallowed by that limit carries forward to future years rather than being lost. Bonus depreciation has no such ceiling — it can drive your business or rental activity into a net loss. For an investor trying to shelter a large first-year deduction against other income, that distinction is decisive: bonus depreciation can create the loss you want, while Section 179 simply stops at zero taxable income.
What real estate actually qualifies for each
Bonus depreciation covers any MACRS property with a recovery period of 20 years or less — the 5-, 7-, and 15-year components a cost segregation study pulls out of a building. Section 179 covers that same tangible personal property, plus a category bonus often misses: qualified real property, which includes roofs, HVAC, fire protection and alarm systems, and security systems installed on nonresidential buildings, as well as Qualified Improvement Property. Neither one applies to the residential or commercial building shell itself (27.5 or 39 years), and Section 179 generally does not reach property used in a residential rental lodging activity — an important limit for landlords to remember.
A side-by-side example
Imagine a cost segregation study on a commercial property identifies $120,000 of 5- and 15-year components plus a $40,000 new HVAC system. With 100% bonus depreciation restored under the One Big Beautiful Bill Act, the $120,000 of short-life property is fully deductible in year one automatically. The HVAC — a building system bonus may not reach on its own for this purpose — can be expensed under Section 179 if you have enough business income to absorb it. Combining the two tools captures $160,000 of first-year deductions from the same project, something neither could do alone.
State conformity: the hidden trap
Federal rules are only half the story. Many states decouple from federal bonus depreciation, requiring you to add it back and depreciate on a slower state schedule, and states set their own Section 179 limits that are often far lower than the federal cap. The result is that your federal and state depreciation can differ substantially, leaving you with separate basis figures to track for years. Before relying on a big first-year federal deduction, check how your state treats both bonus depreciation and Section 179 — the state tax bill can partially offset the federal benefit.
Recapture applies to both
Neither tool escapes recapture. When you sell or convert the property to personal use, deductions taken under bonus depreciation and Section 179 are recaptured — generally as ordinary income under Section 1245 for personal property and short-life components, up to the amount of depreciation claimed. Section 179 has an added wrinkle: if business use of an asset drops to 50% or less before the end of its recovery period, part of the deduction is recaptured immediately. Factor recapture into the decision, because accelerating deductions is a timing benefit, not a permanent exemption.
A brief history of the two incentives
Section 179 is the older tool, long used by small businesses to expense equipment immediately rather than depreciate it. Bonus depreciation arrived as a temporary stimulus measure and was repeatedly extended and enlarged, peaking at 100% under the 2017 Tax Cuts and Jobs Act. The scheduled phase-down that began in 2023 was reversed by the One Big Beautiful Bill Act, which permanently restored 100% bonus for qualifying property acquired and placed in service after January 19, 2025. This history explains why the two tools overlap so much today, and why bonus — with no dollar cap — has become the dominant one for large real estate deductions.
Which one to elect first
When both apply, the order matters. Because Section 179 is limited to taxable income and bonus depreciation is not, a common strategy is to apply Section 179 first to the assets you specifically want expensed, up to your income limit, then let 100% bonus depreciation sweep up everything else — including the amount that would drive you into a loss. Reversing the order can waste the income-limited Section 179 deduction. Tax software applies a default ordering, but for a large cost segregation study it is worth modeling the sequence deliberately with your preparer.
Real-world example with income limits
Suppose your rental and other business activities show $60,000 of taxable income this year, and a cost segregation study on a nonresidential property identifies $200,000 of accelerated assets, including a $45,000 HVAC system. You could elect Section 179 on the $45,000 HVAC (well under your $60,000 income limit), then take 100% bonus on the remaining $155,000 of 5- and 15-year property. The bonus portion can push you to a net loss, while the Section 179 portion stops at income. If instead you tried to Section 179 the full $200,000, $140,000 would be disallowed and carried forward — a far worse result than letting bonus handle it.
Vehicles, equipment, and mixed-use assets
Both incentives reach the tangible personal property a real estate business uses — tools, computers, office equipment, and vehicles used more than 50% for business. Section 179 has special caps for certain vehicles (notably a limit on heavy SUVs), and both require you to watch the business-use percentage. If business use of a Section 179 asset later drops to 50% or less before the end of its recovery period, part of the deduction is recaptured immediately. Keep mileage logs and usage records so the property genuinely supports the deduction you claimed.
Bottom line: use them together
For most real estate investors, the practical answer is not either/or but both. Bonus depreciation, now permanently at 100%, does the bulk of the work on cost-segregated components because it has no dollar cap and can create a loss. Section 179 fills specific gaps — chiefly nonresidential building systems like roofs, HVAC, and security that bonus may not reach — and lets you fine-tune the exact deduction when you do not want a loss. Layer them in the right order, respect the income limits and state conformity rules, and plan for recapture at sale.
Frequently asked questions
Can Section 179 create a loss?
No. It is capped at your business taxable income. Bonus depreciation can create or deepen a loss.
Does bonus depreciation cover a new roof on a rental?
Often not for residential rentals, since roofs are long-life. Section 179 can reach certain nonresidential building improvements.
Do states follow these rules?
Not always. Many states decouple from federal bonus depreciation and Section 179 limits, so check state conformity.
Does Section 179 have a dollar limit?
Yes. Section 179 has an annual expensing cap and phases out once your total qualifying purchases exceed a higher investment threshold. Bonus depreciation has no dollar cap and no spending-based phase-out. Confirm the current-year figures, which are indexed for inflation.
Can I use both Section 179 and bonus depreciation in the same year?
Yes. A common approach is to apply Section 179 first to selected assets (up to the income limit), then let bonus depreciation cover the rest. Bonus can create a loss while Section 179 cannot, so ordering them thoughtfully maximizes the usable deduction.
Does Section 179 apply to residential rental property?
Generally not to the residential rental lodging activity or its structural components, though tangible personal property used in the business may qualify in limited cases. Section 179's real-property category — roofs, HVAC, security systems — applies to nonresidential buildings. Bonus depreciation is usually the primary tool for residential rental cost-seg components.
What happens to my Section 179 deduction if business use drops?
If an asset's business use falls to 50% or less before its recovery period ends, part of the Section 179 deduction is recaptured as ordinary income that year. This immediate-recapture rule does not apply the same way to regular MACRS depreciation.
Which should I take first, Section 179 or bonus?
Generally Section 179 first, up to your business taxable income, then 100% bonus depreciation for the rest. Because Section 179 is income-limited and bonus is not, this order avoids wasting the income-limited deduction and still lets bonus create a loss.
Is bonus depreciation better than Section 179 for real estate?
Usually bonus does the heavy lifting because it has no dollar cap and can create a loss, which most cost-segregation deductions need. Section 179 is best for nonresidential building systems (roofs, HVAC, security) that bonus may not reach, and for fine-tuning when you do not want a loss.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.