Filed an extension on your 2025 return? There's still time for a cost segregation study.

Mid-August is a strange, useful moment in the tax calendar. The April rush is long over, the fall deadlines are visible on the horizon, and a lot of 2025 returns are sitting in draft on a CPA's desk. If yours is one of them, and there's a rental property on it that you bought last year, you're holding an option many investors don't realize they have: there is still time to run a cost segregation study and put the full first-year deduction on the 2025 return that hasn't been filed yet.

Can a cost segregation study still make it onto your 2025 return?

Yes, as long as the return hasn't gone out the door. An extension moves your filing deadline; it doesn't lock anything in. Until the return is actually filed, the depreciation schedule for a property placed in service in 2025 is still being set up for the first time, and a study simply informs how it gets set up. Instead of dropping the whole building into the 27.5-year bucket, the study identifies the components that belong in 5-, 7-, and 15-year buckets, flooring, cabinetry, appliance-dedicated plumbing and electrical, driveways, fencing, landscaping, and your CPA builds the schedule from that.

Done this way, nothing has to be undone later. The first filing is the right filing, no amending, no cleanup. It's the cleanest window a study ever gets, and it closes when the return is filed or the deadline arrives, whichever comes first.

What are the extended deadlines for 2025 returns?

Two dates matter. If the property sits inside a partnership or S corporation, the extended deadline for the entity's 2025 return is September 15, 2026, a month from now, and the K-1s your personal return is waiting on flow from it. If the property is reported directly on your personal return, Schedule E, which is how most 1-4 unit landlords and short-term rental owners hold property, the extended deadline is October 15, 2026.

The entity date is the urgent one. If your rental lives in an LLC taxed as a partnership, the practical runway is measured in weeks, not months.

Why 2025 is a particularly good year to front-load.

Because 100% bonus depreciation is back. The One Big Beautiful Bill restored the full write-off for property acquired (contract signed) after January 19, 2025, which covers most 2025 purchases. The portion of your basis a study reclassifies into short-life buckets becomes fully deductible in the placed-in-service year instead of trickling out over decades. One nuance: if you signed your purchase contract on or before January 19, 2025 and closed later, the older phase-down rates apply instead, we cover the details in our note on the restored 100% rule. Your contract date settles it, which is why we capture it at intake.

The math, for a $475K rental placed in service in 2025.

Say you closed on a $475K single-family rental last summer, placed it in service in August 2025, and extended your personal return. Carve out land first, roughly 20% here, leaving $380K of depreciable basis. A reasonable residential study reclassifies around 22% of that basis, call it $83,600, into 5-, 7-, and 15-year property. With 100% bonus depreciation in effect, that full $83,600 is deductible on the 2025 return your CPA is about to file. At a 32% marginal federal rate, that's roughly $26,800 in year-one federal tax savings, before any state benefit.

Whether the resulting loss is usable this year depends on your situation, passive-activity limits, STR material participation, real estate professional status, but the deduction itself belongs on this return, and even a loss you can't use immediately banks for later rather than disappearing.

How long does a study take, and when is the real cutoff?

Our residential studies run 5-10 business days once your documents are in, no site visit required, the whole thing runs on your closing statement, property details, and photos or listing media. So the math on the calendar is forgiving, but not infinitely so. Your CPA doesn't just need the report in hand; they need runway to build the depreciation schedule into the return and look at the whole picture. For entity returns facing September 15, that means starting now. For personal returns facing October 15, get documents in by late September rather than riding it to the final week.

What if you already filed your 2025 return without a study?

Then this particular window has closed, and the conversation changes. Prior-year depreciation is your CPA's side of the table, and the right move depends on facts they're closest to, so loop them in before ordering anything. For your next acquisition, the cleanest play is deciding early, ideally in the year you buy.

What to do this week.

If your 2025 return is on extension and there's a 2025 property on it, run the rough numbers on the savings estimate, then start the free instant estimate. Two minutes gets you your projected savings and your flat study fee before any payment, in time to actually use it. There are properties where a study doesn't pencil, and we'll say so. If you've got a CPA, we work alongside them, the deliverable is built so they can implement it without translating anything. Start with the free estimate while the window is still open.