How each works
Section 179 allows you to immediately expense the full cost of qualifying property in the year it is placed in service, up to an annual dollar cap (adjusted for inflation each year) and limited to your taxable income from active business activity. The deduction cannot create a loss. Qualifying property includes tangible personal property, certain improvements to nonresidential buildings (QIP, roofs, HVAC, fire protection, alarms, and security systems), and off-the-shelf software.
Cost segregation is an engineering analysis that reclassifies components of a building into shorter-lived depreciable categories. Once reclassified, those components can be combined with bonus depreciation to generate a 100% first-year deduction (under current bonus depreciation rates). Unlike Section 179, bonus depreciation can create a tax loss.
The practical difference: Section 179 is simpler (no study needed, just a tax election) but is capped by income. Cost segregation requires a study and works through bonus depreciation, which can produce passive losses usable against other passive income or carried forward.
Key differences in limits and planning
Income limitation: Section 179 cannot exceed your business income — it can zero out your income but not create a loss. If you have $50,000 of rental income and take $50,000 of Section 179, your income is zero but the deduction stops there. Bonus depreciation from cost segregation has no income cap and can create a paper loss.
Dollar cap: Section 179 has an annual dollar limit (reduced for high-investment years). Bonus depreciation has no dollar cap.
Passive activity interaction: Cost segregation losses are passive and subject to passive activity loss rules. Real estate professionals can offset active income; others may need to carry forward losses. Section 179 deductions on rental property face additional limitations — generally, Section 179 is less useful for passive rental activities than for active business property.
Recapture: Both Section 179 and bonus depreciation generate recapture on sale — Section 179 is Section 1245 recapture (ordinary income); bonus depreciation on personal property is also Section 1245.
Which to use for a rental property
For most individual rental investors, cost segregation combined with bonus depreciation is the better tool because it can generate tax losses (useful if you have passive income or REPS status) and has no income cap.
Section 179 on a rental property is limited: the passive activity rules generally prevent rental losses from sheltering W-2 income, and the income limitation caps the deduction at rental income. One place Section 179 works well in real estate: a QIP improvement on a nonresidential rental with positive net income, where you want to reduce taxable rental income without going below zero.
Frequently asked questions
Can I use Section 179 on a residential rental property?
Section 179 is generally not useful for residential rental properties because the passive activity rules prevent rental losses from offsetting W-2 income, and the income cap limits the deduction to your rental income. Bonus depreciation from cost segregation is usually a better tool.
Can cost segregation create a tax loss?
Yes. When combined with bonus depreciation, cost segregation can generate a paper loss. Whether you can use that loss depends on your passive activity status — real estate professionals can use it against any income; others may carry it forward.
Is Section 179 available for qualified improvement property?
Yes. QIP (interior improvements to nonresidential buildings already in service) qualifies for Section 179, as do roofs, HVAC, fire protection, and security systems added to nonresidential property.
Sources
- IRS Publication 946 — How to Depreciate Property
- IRS — Cost Segregation Audit Techniques Guide
- IRS Publication 527 — Residential Rental Property
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.