1. What a cost segregation study does
A building normally depreciates over 27.5 years (residential) or 39 years (commercial). A cost segregation study breaks the purchase price apart and reclassifies components like flooring, cabinetry, dedicated electrical, and land improvements into 5, 7, and 15-year property, so a large slice of the basis depreciates on much shorter schedules.
On the federal return, that reclassified property also qualifies for bonus depreciation, which restores a 100% first-year write-off for qualifying property acquired and placed in service after January 19, 2025. States set their own rules, which is where Wisconsin comes in.
2. Wisconsin and federal bonus depreciation
Wisconsin fully decouples from IRC 168(k) bonus depreciation for both individual and corporate/franchise tax. Under Wis. Stat. 71.98(3), depreciation, depletion, and amortization are computed under the IRC in effect on January 1, 2014, when no bonus allowance applied to newly placed-in-service property, so bonus has never flowed through for assets placed in service in 2014 or later. The 2025 Wisconsin Schedule I instructions expressly state that OBBBA's permanent 100% bonus for property placed in service after January 19, 2025 (P.L. 119-21 sec. 70301) and the new IRC 168(n) qualified production property election 'do not apply for Wisconsin.' No 2025-2026 Wisconsin legislation conformed to these provisions; general conformity remains static at December 31, 2022, and OBBBA changes apply only if the Legislature acts.
Not a percentage addback with a fixed recovery schedule (unlike MN's 80%/5-year). Individuals use Wisconsin Schedule I (corporations use the Form 4/5S modification schedules): add back all federal depreciation, then subtract depreciation recomputed on a federal Form 4562 marked 'Revised for Wisconsin' using regular MACRS on the Wisconsin basis with no bonus. The disallowed bonus is recovered through normal MACRS deductions over each asset's recovery period, with an adjustment every year until the asset is fully depreciated; the remaining basis difference also adjusts Wisconsin gain or loss when the property is sold.
Worked example
A $1,000,000 building, with and without a study
Illustrative only. A residential rental purchased for $1,000,000 of building basis (land excluded), acquired and placed in service after January 19, 2025.
Building basis
$1,000,000
Reclassified to 5, 7, and 15-year property (25%)
$250,000
Federal first-year deduction at 100% bonus
$250,000
Year 1 on that $250,000 without a study (27.5-year straight line)
about $9,100
On the Wisconsin return, the $250,000 federal bonus deduction is not allowed. Not a percentage addback with a fixed recovery schedule (unlike MN's 80%/5-year). Individuals use Wisconsin Schedule I (corporations use the Form 4/5S modification schedules): add back all federal depreciation, then subtract depreciation recomputed on a federal Form 4562 marked 'Revised for Wisconsin' using regular MACRS on the Wisconsin basis with no bonus. The disallowed bonus is recovered through normal MACRS deductions over each asset's recovery period, with an adjustment every year until the asset is fully depreciated; the remaining basis difference also adjusts Wisconsin gain or loss when the property is sold.
Model your own numbers with the tax strategy projector.
3. Section 179 in Wisconsin
Uniquely, Wisconsin's Section 179 conformity is rolling: Wis. Stat. 71.98(4) adopts secs. 179, 179A-179E 'of the federal Internal Revenue Code in effect for the year in which property is placed in service' for taxable years beginning after Dec 31, 2013. That means the OBBBA-expanded limits flow through automatically, so for 2025 Wisconsin allows the full federal $2,500,000 expensing limit with the $4,000,000 phase-out threshold (inflation-indexed thereafter), plus the same business-income limitation. WI DOR confirms Wisconsin follows the same maximum dollar and business income limitations as federal. Taxpayers may even elect different 179 amounts for federal vs. Wisconsin purposes. The old $25,000/$200,000 Wisconsin caps only applied to taxable years beginning before 2014. Caveat for landlords: 179 is statutorily unavailable for most residential rental building components regardless of state, so it only partially substitutes for lost bonus.
4. Does it still help in Wisconsin?
Yes. The IRC as of January 1, 2014 includes full MACRS, so Wisconsin honors the 5-, 7-, and 15-year recovery periods (and 27.5/39-year building lives) that a cost segregation study produces; reclassified assets are depreciated on those accelerated schedules (including 200%/150% declining balance) on the Wisconsin return, just without the federal 100% first-year bonus, and rolling Section 179 conformity lets eligible 5/7-year personal property and qualifying nonresidential components be expensed up to the federal $2.5M limit.
- •Wisconsin has a split personality: general IRC conformity is static at Dec 31, 2022, depreciation is frozen at the Jan 1, 2014 IRC, but Section 179 is rolling conformity, so the OBBBA $2.5M/$4M 179 limits apply in Wisconsin even though 100% bonus does not.
- •Because Section 179 follows current federal law while bonus is disallowed, 179 expensing is the primary first-year write-off lever on the Wisconsin return; WI DOR explicitly notes 179 'operates independently of, and is claimed prior to' 168(k) bonus.
- •Taxpayers may elect a different Section 179 amount for Wisconsin than for federal purposes, a planning lever most states do not offer.
- •Wisconsin adopted the CARES Act technical correction giving qualified improvement property a 15-year MACRS life (2021 Wis. Act 1), so QIP is 15-year for Wisconsin too, but without bonus.
- •Annual Schedule I adjustments are required for every bonus-affected asset until fully depreciated, and affected federal forms (4562, 8582, Schedule E) must be recomputed and attached marked 'Revised for Wisconsin', a real compliance burden for rental owners with passive-loss limitations.
- •Wisconsin basis exceeds federal basis after bonus is claimed federally, so Wisconsin gain on sale is smaller (less recapture) than federal gain; for assets placed in service before Jan 1, 2014, Wisconsin and federal basis were equalized via a 5-year transition deduction under 2013 Wis. Act 20.
- •Wisconsin also declined OBBBA's new IRC 168(n) 100% deduction for qualified production property (nonresidential manufacturing real estate), and does not apply the federal excess business loss limitation under sec. 461(l).
5. The exit: recapture and timing
The accelerated deductions come back into view when you sell. Gain attributable to the 5, 7, and 15-year property is Section 1245 recapture, taxed at ordinary rates, and the straight-line depreciation on the building itself is unrecaptured Section 1250 gain, taxed at up to 25%. A study does not create that bill, it moves deductions forward, but the timing of the sale decides how much of the benefit you keep.
Two levers manage the exit. A 1031 exchange defers both flavors of recapture along with the rest of the gain, and simply holding the property lets the time value of the early deductions do its work; most owners want a 3 to 5 year horizon before a taxable sale for the math to stay comfortably positive. Model the exit before you commission the study, not after.