What is the difference between 27.5-year and 39-year depreciation? The difference is a single classification test built into IRC Section 168(c): a building depreciates over 27.5 years if 80% or more of its gross rental income comes from residential dwelling units, and over 39 years if it does not. The test applies once, to the whole building, which is why a mixed-use property with ground-floor retail and apartments above it usually lands entirely on one schedule rather than splitting floor by floor. For a passive investor, the distinction changes the size of an annual deduction and interacts directly with the broader tax benefits of commercial real estate.
Key Takeaways
- IRC Section 168(c) sets two MACRS recovery periods for real property: 27.5 years for residential rental property and 39 years for nonresidential real property.
- A building qualifies for the 27.5-year schedule only if 80% or more of its gross rental income comes from residential dwelling units, tested every year.
- The 80% test applies to the entire building at once, so a mixed-use property that fails it depreciates the entire building, including any residential units, over 39 years.
- Both schedules require the straight-line method and the mid-month convention; neither bonus depreciation nor Section 179 changes the building's own recovery period.
- On a hypothetical $10,725,000 depreciable basis, the 27.5-year schedule deducts about $390,000 a year while the 39-year schedule deducts about $275,000, a gap of roughly $115,000 annually.
- Nonresidential real property was depreciated over 31.5 years before a 1993 law change extended it to 39 years for property placed in service after May 12, 1993.
| Annual deduction on a hypothetical $10,725,000 depreciable basis | |
|---|---|
| 27.5-year (residential rental) | $390K |
| 39-year (nonresidential real property) | $275K |
Illustrative arithmetic to show the mechanism, not market data.
What Decides Whether a Building Gets 27.5 Years or 39 Years
Every building depreciated under the Modified Accelerated Cost Recovery System falls into one of exactly two real property categories, and the category, not the owner's preference, decides the recovery period. Residential rental property recovers its cost over 27.5 years. Nonresidential real property, the category that covers offices, retail, warehouses, and most of commercial real estate, recovers its cost over 39 years.
The classification is not an election a taxpayer makes on a return. It is a factual test applied to the building itself, and 26 U.S.C. § 168 sets out both the recovery periods and the definitions that sort a building into one category or the other. IRS Publication 946, How To Depreciate Property, is the practical reference most preparers use, and it restates the same test in plainer language: a building qualifies as residential rental property only if it clears a specific income threshold, covered in the next section.
Most commercial real estate investors never have to run this test, because an office building, a freestanding retail store, or an industrial warehouse has no dwelling units at all and falls into the 39-year category automatically. The test becomes consequential only for a narrower set of properties: apartment buildings, mixed-use buildings with residential units above commercial space, and any property where the mix of tenants is close enough to the line that the classification is not obvious on its face.
The 80 Percent Test, and How Income Is Counted
A building qualifies as residential rental property only if 80% or more of its gross rental income for the tax year comes from dwelling units, a test defined in Section 168(e)(2) and explained further in IRS Publication 527, Residential Rental Property. A dwelling unit means a house or an apartment used to provide living accommodations, and the definition specifically excludes a unit in a hotel, motel, or similar establishment where more than half the units are used on a transient basis.
Three details decide how the percentage actually gets calculated. First, the test looks at gross rental income, not square footage or unit count, so a building with many small apartments and one large ground-floor restaurant space can fail the test even though residential units outnumber commercial ones, if the restaurant's rent is large enough relative to the total. Second, the test is applied every tax year rather than once at purchase, so a building's classification can, at least in theory, move from one side of the line to the other as a lease mix changes, though in practice most buildings sit well clear of the boundary in one direction or the other. Third, if an owner personally occupies part of the building, the fair rental value of that space counts as dwelling-unit income for purposes of the test, which matters for a small multifamily property where an owner lives in one unit.
None of this test applies to a building with no residential units at all. A single-tenant retail building, an office building, or an industrial property has a gross rental income figure that is 0% dwelling-unit income by definition, which is why the 39-year schedule is the default assumption for nearly everything in commercial net lease and why the 80% question only becomes live once residential units enter the picture.
Why a Mixed-Use Building Usually Lands on One Schedule
The 80% test is applied to the building as a whole rather than floor by floor, which means a mixed-use property with ground-floor retail and residential units above it generally depreciates entirely over one schedule, not a blend of the two. A building that clears the 80% threshold depreciates every square foot, including the commercial ground floor, over 27.5 years. A building that fails the threshold depreciates every square foot, including the residential units above, over 39 years.
That whole-building outcome surprises owners who assume a split is available simply because a split would seem logical. The test does not ask what each portion of the building is used for. It asks what share of the building's total rental income came from dwelling units, and the answer to that one question sets the recovery period for the entire structure. A four-story building with three floors of apartments and one floor of retail can still land on the 39-year schedule if the retail tenant's rent is large enough relative to the building's total income, even though three-quarters of the floor plan is residential.
This is also a separate question from cost segregation, covered further down. Cost segregation identifies components inside a building that qualify for shorter recovery periods on their own terms, such as certain electrical, flooring, and site improvements. It operates after the building's overall classification, 27.5-year or 39-year, has already been determined, and it cannot change that underlying classification. The two questions are often confused because both involve recovery periods, but they are decided under different rules and at different points in the analysis.
How Much the Choice of Schedule Actually Costs
The gap between a 27.5-year schedule and a 39-year schedule is a straightforward division problem, and it compounds every year a property is held. A shorter recovery period spreads an identical depreciable basis across fewer years, which means a larger annual deduction for as long as the shorter schedule runs, and a correspondingly smaller deduction on the 39-year side of the comparison.
In a hypothetical using round numbers chosen for arithmetic rather than drawn from any transaction, a property with a depreciable basis of $10,725,000 produces an annual straight-line deduction of about $390,000 on a 27.5-year schedule and about $275,000 on a 39-year schedule, a difference of roughly $115,000 every year the schedule applies. As the comparison shows, the two schedules are not a small rounding difference. Over a multi-year hold, that annual gap adds up to a meaningfully larger cumulative deduction on the residential side of the line.
None of this changes how much total depreciation exists over the full life of a building, since both schedules eventually recover the entire depreciable basis. What changes is the timing, and timing has real value. A larger deduction taken sooner is worth more than the same deduction taken later, both because of the time value of money and because depreciation taken now reduces this year's taxable income rather than a future year's. A larger deduction also means a larger depreciation recapture obligation calculated at sale, since recapture is measured against the depreciation actually claimed, so neither schedule is a one-directional advantage without a cost attached somewhere in the hold.
Straight-Line, Mid-Month Convention, and Why Neither Schedule Accelerates
Both the 27.5-year and the 39-year schedules use the straight-line depreciation method, and neither allows the accelerated declining-balance methods available to shorter-lived personal property. Section 168(b)(3) requires straight-line depreciation for residential rental property and nonresidential real property specifically, which means the deduction is the same dollar amount every full year rather than front-loaded the way a 5-year or 7-year asset can be.
Both schedules also use the mid-month convention, which treats a property as placed in service, or disposed of, in the middle of the month regardless of the actual date. A building placed in service on the 3rd of a month and one placed in service on the 28th of the same month receive the identical first-year deduction under this convention, because both are treated as having been in service for half that month. The same convention applies in reverse at sale, which is why the year of disposition always produces a partial-year deduction rather than a full one.
The practical effect of these two shared rules is that neither the 27.5-year nor the 39-year schedule rewards an owner for timing a purchase within a particular month, and neither one can be sped up through an accounting method election the way bonus depreciation can speed up a shorter-lived component. The only lever available on the building shell itself is the recovery period assigned by the classification test, which is the entire subject of this guide.
Where Cost Segregation Fits Once the Schedule Is Set
A cost segregation study separates a building's cost into components with their own, shorter recovery periods, commonly 5, 7, and 15 years, and that study is performed after the building's overall classification as residential or nonresidential has already been fixed by the 80% test. The guide to how a cost segregation study splits a building into separate depreciation schedules covers that process in detail, including what qualifies for the shorter buckets and what stays on the 39-year or 27.5-year shell regardless of how the study is performed.
For an investor holding property through a fund rather than directly, none of this classification work is performed by the investor. The entity makes the determination, commissions any cost segregation study, and reports the resulting depreciation as an allocated figure on each investor's Schedule K-1, often as a loss in a year the fund also distributed cash. Whether a specific fund's properties sit on the 27.5-year or 39-year schedule is rarely stated explicitly in investor communications, because the distinction matters to the fund's own return preparation rather than to the cash an investor actually receives.
Every determination described in this guide, including which schedule a specific building falls under, whether a mixed-use property clears the 80% test in a given year, and what a cost segregation study would actually be worth on a particular return, depends on facts specific to the property and the taxpayer. Freedom Commercial Real Estate does not provide tax advice, and nothing in this guide is tax advice. These questions belong with your own CPA or tax advisor, who can review the building's actual rent roll and depreciation schedule.
Freedom Commercial Real Estate publishes guides like this one so investors can understand how a building's own depreciation schedule gets set before a cost segregation study or a K-1 ever enters the picture. Questions about anything covered here, or a tax mechanic worth explaining next, can go straight to the team at info@freedomcre.net.
Frequently Asked Questions
Q: How does the 80% test apply to a building with both apartments and a ground-floor retail tenant?
A: The test compares the dwelling units' share of the building's total gross rental income against the ground-floor retail rent and everything else combined. If dwelling-unit rent reaches 80% or more of that total, the entire building, including the retail space, depreciates over 27.5 years. If it does not, the entire building, including the apartments, depreciates over 39 years. The test is not applied separately to each floor.
Q: Can a building's classification change from one tax year to the next?
A: The 80% test is applied for each tax year, so a building whose tenant mix shifts meaningfully, for example after a large commercial tenant moves out and the space converts to apartments, could in theory move from one classification to the other. In practice most buildings sit well on one side of the 80% line, and a change in classification is unusual enough that it is worth confirming with a tax advisor before assuming it applies to a specific property.
Q: Does a cost segregation study change whether a building uses the 27.5-year or 39-year schedule?
A: No. Cost segregation identifies components inside a building, such as certain electrical systems, flooring, and site improvements, that qualify for their own shorter recovery periods. It does not change the recovery period of the building shell itself, which is set by the 80% residential income test before any cost segregation study is ever performed.
Q: Has nonresidential real property always depreciated over 39 years?
A: No. Nonresidential real property placed in service before May 13, 1993 generally used a 31.5-year recovery period. A 1993 law change extended that period to 39 years for nonresidential real property placed in service on or after that date, and 39 years has applied to new acquisitions ever since.
Q: Does bonus depreciation shorten the 39-year schedule for a commercial building itself?
A: No. Bonus depreciation generally applies only to property with a recovery period of 20 years or less, which excludes the building shell on both the 27.5-year and 39-year schedules. It can apply to shorter-lived components identified through a cost segregation study, which is a separate question from the building's own recovery period.
Sources
- Internal Revenue Service, Publication 946: How To Depreciate Property
- 26 U.S.C. § 168, Accelerated Cost Recovery System, Legal Information Institute
- Internal Revenue Service, Publication 527: Residential Rental Property
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