Wisconsin doesn’t allow bonus depreciation. Is a cost segregation study still worth it here?

Every Wisconsin investor who reads about 100% bonus depreciation eventually runs into the same sentence from their accountant: Wisconsin doesn’t allow it. The federal number was enormous. The state number is zero. And the natural conclusion, the one we hear from Milwaukee and Madison and the Fox Valley most weeks, is that a cost segregation study must be a federal-only play with nothing in it for the Wisconsin side of the return.

That conclusion is half right. The half that’s wrong is worth real money on a duplex.

Does Wisconsin allow bonus depreciation?

No, and it hasn’t for over a decade. For assets placed in service in taxable years beginning on or after January 1, 2014, Wisconsin computes depreciation under the Internal Revenue Code as it stood on January 1, 2014, and the state expressly disallows the additional first-year allowance under IRC §168(k). The Wisconsin Department of Revenue is blunt about it: bonus depreciation is not allowed for Wisconsin purposes.

The One Big Beautiful Bill didn’t change that. Its restoration of 100% bonus depreciation for property acquired after January 19, 2025 is a federal restoration only, and Wisconsin did not follow. What that leaves you with is two depreciation schedules for the same building: a federal one and a Wisconsin one, with the difference reported on Schedule I alongside your Form 1. Your CPA is already doing this for the building itself. A study doesn’t create the second schedule; it just fills it in more precisely.

So does a cost segregation study still help a Wisconsin rental?

Yes, because bonus depreciation and cost segregation are two different rules, and Wisconsin only rejected one of them.

A study doesn’t manufacture a deduction. It sorts your purchase price into the recovery periods the code already assigns: flooring, cabinetry, appliance-dedicated plumbing and electrical, window treatments, driveway, fencing, and site landscaping are not structural 27.5-year building. Bonus depreciation is the separate federal provision that lets you take that short-life property all at once instead of over its class life.

Wisconsin disallows the second part and keeps the first. The state still recognizes 5-, 7-, and 15-year MACRS class lives. So everything a study reclassifies still comes off your Wisconsin return dramatically faster than 27.5-year straight line, it simply comes off over five to fifteen years rather than in a single year. Without a study, none of it does, because absent an engineering-based allocation the whole building sits in the 27.5-year bucket on both returns.

The math on a $520,000 Milwaukee duplex.

Say you close on a $520,000 duplex on Milwaukee’s northwest side and place it in service in 2026. Carve out land first, call it 20% for a city lot, leaving $416,000 of depreciable basis. A residential study on a property like this typically reclassifies around 24% of that basis into short-life property, roughly $99,800, split about $70,000 into 5-year and $29,800 into 15-year.

Federal side. Because the property was acquired after January 19, 2025, 100% bonus applies, so the full $99,800 is deductible in 2026. At a 32% marginal federal rate that’s about $31,900 of first-year federal tax savings.

Wisconsin side. No bonus, so the same $99,800 runs on its normal MACRS schedule. First-year depreciation on that slice comes to roughly $15,500 — about $14,000 from the 5-year property and $1,500 from the 15-year. Had it all stayed in the 27.5-year building, Wisconsin would have given you about $3,600 on that same $99,800. You’re roughly $11,900 ahead on the Wisconsin return in year one, worth about $630 at the 5.3% bracket, or closer to $910 at Wisconsin’s 7.65% top rate.

Year one is the least impressive year. Run it out five years and the 5-year property is fully written off for Wisconsin while the 27.5-year alternative has delivered barely a fifth of it. Cumulatively you’re around $63,000 of additional Wisconsin deduction pulled into the first five years, on the order of $3,300 of Wisconsin tax deferred out of your early ownership and into later years.

Where the Wisconsin benefit actually is.

It is timing, not magic, and worth being honest about the size of it. The federal number will always be the headline on a Wisconsin property, because 100% bonus is a bigger lever than a class-life change. The Wisconsin piece is a few hundred to a few thousand dollars of deferral in the early years, and it costs nothing extra to capture, because the same study produces both schedules. What you should not do is skip the study on the theory that Wisconsin gives you nothing.

Two Wisconsin wrinkles to raise with your CPA.

First, your Wisconsin basis will diverge from your federal basis, which matters on sale rather than during ownership: the state never allowed the bonus deduction, so it also isn’t recapturing it, and the Wisconsin gain calculation follows the Wisconsin schedule. Second, the state does allow §179 expensing under its own limitations, which may be a lever depending on how your rental activity is structured. Both are your CPA’s call, and both are easier to make once the basis is actually sorted.

If you’re closing before December 31.

Placed-in-service date, not closing date, decides which return the deduction lands on, so a Q4 Wisconsin purchase needs the property genuinely ready and available for rent before year-end. Our residential studies run 5-10 business days once documents are in, with no site visit, so the calendar is forgiving, but December is not the month to start. If you’re weighing a fourth-quarter close, the year-end timeline note walks through what has to happen and when. If you own property in more than one state, our state conformity overview covers how other states handle this.

What to do next.

Run your own numbers on the savings estimate first, using your purchase price and a realistic land allocation. There are Wisconsin properties where a study doesn’t pencil — a small purchase price, a mostly-land parcel, an owner with no way to use the loss — and we will tell you so rather than sell you a report. Every study we produce is audit-ready and built so your CPA can implement it without translating anything.