Two schedules, one building, and a test that picks the winner
Every mixed-use owner eventually asks the same question: is my building residential or commercial for depreciation? The tax code answers with a bright-line test. If 80% or more of the building's gross rental income is rental income from dwelling units, the whole building is residential rental property on the 27.5-year schedule; below that line, it is nonresidential 39-year property. One test, eleven and a half years of schedule difference on every non-reclassified dollar.
That makes mixed-use the property type where classification planning and cost segregation interact most directly. The study reclassifies the same kinds of components either way (apartment interiors, retail build-outs, site work), and Engineered Tax Services reports typical acceleration of 22% to 35% of basis for mixed use. But the test result determines the schedule for the 65% to 78% that remains, and because the test runs on gross rental income year by year, the answer can change as your tenant mix changes.
This page covers the test, the study, and the lease-mix planning that sits between them.
Rent roll composition is partially within your control. A building sitting at 78% dwelling-unit income is one lease renewal away from dropping every non-reclassified dollar onto the 27.5-year schedule. Model the test before signing the next commercial lease, not after.
The 80% Test, Precisely
How the residential determination actually computes.
Section 168(e)(2)(A) defines residential rental property as a building where 80% or more of gross rental income is rental income from dwelling units. The test runs on gross rental income for the taxable year, dwelling units mean houses or apartments providing living accommodations (not units in a hotel or motel run on a transient basis), and if the owner occupies a unit, a fair-rental value for it enters both sides of the fraction.
Three practical consequences follow. First, the whole building takes one schedule; there is no floor-by-floor split of the structure itself when the test is met or failed. Second, the test can flip year to year as the rent roll moves, and the depreciation method follows the property's classification in the year placed in service, with changes handled under the accounting method rules, so the placed-in-service year determination matters most. Third, ground-floor commercial rent is often high per square foot, which means a physically small retail strip can fail the test for a mostly-residential building.
When a building's use genuinely shifts (say, converting retail floors to apartments), the change-in-use rules adjust the schedule prospectively. That mechanical corner is beyond this page; the point is that the classification deserves an annual glance, not a one-time assumption.
| Income source | Annual gross rent | Dwelling unit income? |
|---|---|---|
| 12 apartments, floors 2-4 | $372,000 | Yes |
| Corner restaurant, ground floor | $84,000 | No |
| Boutique retail bay, ground floor | $41,000 | No |
| Result: $372,000 / $497,000 = 74.8% | Below 80% | Entire building is 39-year nonresidential |
Same building with the restaurant space converted to two more apartments at $62,000 combined: $434,000 / $475,000 = 91.4%, and the entire building moves to the 27.5-year schedule.
What the Study Moves in a Mixed-Use Building
Both tenant profiles contribute short-life property.
| Component | MACRS life | Source |
|---|---|---|
| Apartment interiors: flooring, cabinetry, appliances | 5-year | Residential floors |
| Retail/restaurant build-out finishes owned by landlord | 5-year | Commercial floors; decorative millwork, specialty lighting |
| Dedicated electrical and plumbing serving tenant equipment | 5-year | Commonly restaurant-driven |
| Awnings, exterior signage structures | 5- or 15-year | Classification depends on attachment and function |
| Sidewalk vaults, rear parking, refuse enclosures, landscaping | 15-year | Site improvements |
| Facade, structure, roof, elevators, core systems | 27.5- or 39-year | Per the 80% test result |
Landlord-owned versus tenant-owned improvements matter: only basis you own enters your study. Tenant-funded build-outs belong on the tenant's schedule.
Worked example (illustrative)
Corner building, $2.4M purchase, apartments over retail
- Purchase price
- $2,400,000
- Land allocation
- ($480,000)
- Depreciable basis
- $1,920,000
- Reclassified to 5-year
- $310,000
- Reclassified to 15-year
- $225,000
- Total accelerated (27.9% of basis)
- $535,000
- Year 1 with 100% bonus
- ~$535,000 plus straight-line on the remainder
- Remainder schedule if test passed / failed
- 27.5 years / 39 years on $1,385,000
Illustrative numbers inside the ETS 22-35% range. Note how the 80% test result changes the annual deduction on the remainder by roughly $15,000 per year for decades, independent of the study.
Hypothetical case study
The owner who renewed a lease into the wrong schedule
This is a hypothetical, illustrative composite, not an actual client or an actual result. Savings vary with your income, entity, state, and how usable the losses are.
A hypothetical owner holds a four-story building at 82% dwelling-unit income: comfortably residential, 27.5-year schedule. The ground-floor tenant proposes a renewal at a 40% rent increase. Signed as offered, dwelling-unit income drops to 77% and the building fails the 80% test going forward, a result nobody in the negotiation priced.
Modeled in advance, the owner had options: take the increase and accept the classification consequence, restructure part of the payment as a CAM reimbursement rather than rent, or hold the line closer to the threshold. In this hypothetical the owner took the increase knowingly, because the cash was worth more than the schedule, but the decision was made with the tax effect on the table.
Hypothetical composite. The takeaway: in mixed-use, lease negotiations are depreciation decisions.
The Mixed-Use Owner's Stack
QIP, dispositions, and the books that keep two tenant types straight.
- Qualified Improvement Property: interior improvements to the commercial portions of a 39-year building can qualify as 15-year QIP, bonus-eligible, which softens the blow of failing the 80% test.
- Partial dispositions on retail turnover: each re-tenanting that demolishes a prior build-out is a write-off opportunity if the study documented the components.
- Separate commercial and residential books: security deposits, CAM reconciliations, and occupancy patterns differ by floor, and clean segmentation feeds both the 80% test and lender reporting. Our landlord accounting service structures this.
- The passive-loss gates apply as usual for individual owners; REPS or passive income decides usability of the study's loss.
- 1031 exchanges work for mixed-use like any real property, and the classification analysis restarts with the replacement building.
Taxstra Tip
Track the 80% computation in your year-end close every year, using gross rental income by unit. It is a ten-minute spreadsheet that catches classification drift before it compounds, and it doubles as documentation if the schedule is ever examined.
How We Handle Mixed-Use Studies
Classification first, engineering second, return third.
We resolve the 80% test and document the classification, then coordinate the engineering through Engineered Tax Services, whose reports allocate basis across both tenant profiles. Taxstra implements the schedules, files Form 3115 where a look-back or classification correction is needed, and monitors the test annually as part of the engagement.
Disclosure: Taxstra may receive a referral fee if you engage ETS through links on this page.
Estimate Your Savings
A quick estimate from the ETS calculator, then a study only if the numbers justify it.
Estimate Your Cost Segregation Savings
Run your property through the Engineered Tax Services savings calculator for a quick estimate, then have Taxstra pressure-test the number against your full tax picture.
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Calculator provided by Engineered Tax Services. Estimates are educational only and depend on an engineering-based study of your specific property; results are not individualized tax advice.
Disclosure: Taxstra may receive a referral fee if you engage Engineered Tax Services through links on this page. That relationship does not change your price, and it is not a recommendation for your specific situation.
See What a Study Could Do for Your Property
Engineered Tax Services performs the engineering-based study. Taxstra turns the report into actual tax savings on your return and coordinates the strategy around it. Start with their calculator or real case studies.
Want proof first? See real client case studies from ETS with the numbers behind each study.
Disclosure: Taxstra may receive a referral fee if you engage Engineered Tax Services through links on this page. That relationship does not change your price, and it is not a recommendation for your specific situation.
What to check before you order a study
The pre-study review that decides whether the deduction is actually usable.
Compute the 80% gross rental income test from the actual rent roll before setting any schedule.
Separate landlord-owned build-out basis from tenant-funded improvements.
Document the land allocation; corner commercial parcels often carry aggressive assessor land ratios worth reviewing.
Model upcoming lease renewals against the 80% threshold before signing.
Check QIP eligibility for planned interior work if the building is (or becomes) 39-year property.
Estimate the study benefit with the cost segregation estimator using the correct baseline schedule.