Cost segregation and the partial disposition election: writing off the roof, HVAC, or kitchen you tore out.

You gut the kitchen in a rental, tear off a failing roof, or swap out an old furnace. You already know the new component gets capitalized and depreciated. What most landlords miss is the other half of the transaction: the old component is gone, and its remaining un-depreciated basis can usually come off your return as a loss right now. That’s the partial disposition election, and it’s one of the most overlooked deductions in residential real estate.

The catch is that you can only claim it if you know the basis of the thing you removed — and that number almost never appears on your closing statement or depreciation schedule. That’s where a cost segregation study earns its keep.

What is a partial disposition election?

When you bought your rental, the IRS treats the whole building as a single asset depreciated over 27.5 years. But a building is really a bundle of components — roof, HVAC, plumbing, the kitchen, the flooring. Under the tangible property regulations (Reg. §1.168(i)-8), when you retire one of those structural components and replace it, you can elect to treat the retirement as a disposition of just that piece. You recognize a loss equal to the old component’s remaining basis, and you stop depreciating something that no longer physically exists.

Without the election, two awkward things happen. You keep depreciating a roof that’s in a landfill, stacked on top of depreciating the new roof — two roofs on the books, one in reality. And that phantom basis follows you to the sale, where it gets caught up in depreciation recapture even though you never got the benefit of writing it off.

Why would you write off something you just replaced?

Because the loss is real and it’s ordinary. The remaining basis of the retired component comes off as an ordinary loss in the year of the disposition — not a capital loss, not something spread over decades. For an investor in a decent bracket, that’s cash back on this year’s return, in the same year you’re already spending money on the renovation.

There’s a quieter benefit too. Removing the old component’s basis from the building means there’s nothing left to recapture on it later — you’ve converted a slow, unfavorable future recapture into a clean deduction today.

How does cost segregation make the election possible?

Here’s the practical wall people hit: to write off the old roof, you have to know the old roof’s basis. Your purchase records lumped it into one building number years ago. The regulations let you use any reasonable method to figure out the retired component’s share of that basis — but “reasonable” has to mean something you can defend.

A cost segregation study is exactly that method. The same engineering-based allocation that breaks a building into 5-, 7-, 15-, and 27.5-year buckets can isolate what a specific component was worth at purchase, then discount it back to reflect the year you bought. That gives you a documented, audit-ready figure for the retired piece instead of a guess. It’s the same discipline we describe in what a cost segregation study actually reclassifies, pointed at a single component rather than the whole property.

A worked example: replacing the roof on a $360K rental.

Say you bought a single-family rental in 2019 with $360,000 of depreciable building basis (land already carved out). In 2026 the roof fails and you replace it for $18,000.

An engineering allocation puts the original roof at about $28,000 of that 2019 building basis. Over roughly seven years of depreciation you’ve written off about $7,100 of it, leaving a remaining basis of roughly $20,900. Make the partial disposition election and that $20,900 comes off as an ordinary loss in 2026. At a 32% marginal rate, that’s about $6,700 in tax savings this year — on a component you were going to throw away regardless.

Skip the election and you get none of that now. Instead you’d keep depreciating the old $20,900 for another two decades, depreciate the new roof on top of it, and hand the old roof’s depreciation back as recapture at sale. The election trades that friction for a deduction you can use now.

What about the new component you installed?

The replacement gets capitalized and depreciated going forward. A new roof is part of the building structure, so it rides the 27.5-year schedule. But many renovations also add genuine short-life property — new appliances, cabinetry, flooring, landscaping — and because those items are acquired after January 19, 2025, they can qualify for 100% bonus depreciation as 5- or 15-year property. A study run on the renovation can catch both sides at once: the write-off of what came out, and the accelerated depreciation of what went in.

What’s the catch on timing?

This is the part to plan around. The partial disposition election generally has to be made on a timely filed return — including extensions — for the tax year in which the disposition happens. Miss that window and the deduction is much harder to recover. So the time to think about it is the year you do the work, not years later when you’re reconstructing what happened. If you have a renovation planned or recently finished, that’s the moment to loop in your CPA and get the component basis documented while the project details are fresh.

Is it worth the trouble on a residential rental?

Often, yes — especially on larger swaps like a roof, an HVAC system, or a full kitchen or bath gut, where the retired basis is meaningful. On a small cosmetic refresh, the numbers may not justify the analysis. It comes down to the size of the component and your marginal rate. Our savings estimate is a fast first cut, and we’re glad to talk through whether a partial disposition makes sense alongside a study on your property.