It happens more often than you'd think. An investor has a busy year, closes on a duplex in the spring and a furnished condo in the fall, and by the time the return comes together there are two new properties on it. Then the question lands: run a cost segregation study on both, or pick one and save the other for a year when the deduction is worth more?
The instinct to stagger is understandable. It's also usually built on a misreading of how the timing works.
Can you run a cost segregation study on two rentals in the same year?
Yes. There is no limit, written or practical, on how many properties you can study in a tax year. Each property gets its own study, its own asset schedule, and its own line on the depreciation schedule your CPA builds. They don't interact, they don't compete, and one doesn't dilute the other. Two studies in one year is simply two studies.
What matters far more than the count is when each property was placed in service, meaning ready and available to rent. That date, not your closing date, decides which tax year each property's first-year deduction belongs to. Two rentals placed in service in the same year belong on the same return.
So why does staggering feel like the safer move?
Because people assume the deduction is a thing they're allowed to move. It isn't. Studying one property now and the other "next year" doesn't shift the second property's first-year deduction into next year's return; it just means the second one spends its first year on the straight 27.5-year schedule, and sorting that out later becomes a conversation with your CPA rather than a clean first filing.
Both properties also share the same bonus-depreciation posture. Under the One Big Beautiful Bill, 100% bonus depreciation applies to property acquired (contract signed) and placed in service after January 19, 2025. Two properties bought in the same year are almost always on the same side of that line, so there's no timing advantage waiting for one of them.
Does stacking two deductions into one year waste them?
Here's the straight answer: the deduction isn't wasted, but it may not all be usable this year.
If your rentals are passive, and for most long-term landlords they are, the losses a study creates offset passive income first. Anything beyond that is suspended. Suspended is not lost: it carries forward indefinitely, it offsets passive income in future years, and it releases in full when you sell. We walk through exactly how that works in our note on what happens to losses you can't use this year.
The answer changes if you can treat the losses as non-passive, through real estate professional status or, for a short-term rental, through material participation. Then a stacked year is often the best outcome available, because both deductions land against ordinary income at once.
The math on two rentals placed in service in the same year.
Say you closed on a $520,000 duplex in April and a $365,000 furnished short-term rental condo in September, and both were rent-ready the month you closed.
On the duplex, carve out land first, roughly 20% of the purchase price here, leaving $416,000 of depreciable basis. A reasonable residential study reclassifies around 22% of that, about $91,500, into 5-, 7-, and 15-year property.
On the condo, land allocation runs lower, call it 15%, leaving about $310,000 of depreciable basis. Because it's furnished and short-term, the reclassified share runs higher, around 26%, or roughly $80,700, since furniture, appliances, and dedicated fixtures are all short-life property. Those are the assets STR owners most often leave on the 27.5-year clock.
Together that's roughly $172,200 of basis moved into short-life buckets, fully deductible in the placed-in-service year with 100% bonus depreciation in play. At a 32% marginal federal rate, that's about $55,100 in first-year federal tax savings, before any state effect. The remaining building basis keeps depreciating on the normal 27.5-year schedule; nothing is given up to get the acceleration.
If your passive income that year is, say, $18,000, most of that $172,200 is suspended rather than deducted immediately. It still belongs on this return, and it still shows up later.
Which property should you study first if you only do one?
Sometimes the honest answer is that only one is worth it right now. When that's the case, the ranking is straightforward:
Run the property with the higher depreciable basis and the higher expected reclassification percentage first. A furnished short-term rental usually beats an unfurnished long-term rental at the same price, and a property with real site work, driveway, fencing, landscaping, beats a condo with none. Better still, run the property whose losses you can actually use, which in practice means the short-term rental if you materially participate in it. There are properties where a study doesn't pencil at all, and we'll tell you that rather than sell you one.
What if one of them was placed in service in an earlier year?
Then the two aren't really a pair and don't get decided together. A property already sitting on a filed return has prior-year depreciation attached to it, and the right move depends on facts your CPA is closest to, so loop them in before ordering anything on that one. The property placed in service in the current open year is the clean case, and the one to act on now.
What to do before your extended deadline.
If your return is on extension and there are two 2025 properties on it, the calendar is the constraint, not the count. Our residential studies run 5-10 business days once documents are in, and two properties run in parallel rather than back to back, but your CPA still needs runway to build both schedules into the return. If you're working against the October 15 extended deadline, documents in by late September is the realistic line.
Run both properties through the savings estimate and compare them side by side. Start with the free estimate and we'll tell you whether one, both, or neither is worth doing.