Bought a Rental in 2026? Here's Why December 31 Matters

Quick Answer: Depreciation, including the 100% bonus depreciation that makes a cost segregation study pay off, doesn’t start when you close. It starts when the property is placed in service, which the IRS defines as ready and available for rent, even if no one has booked it yet. To claim the deduction on your 2026 return, the rental has to be ready and available for guests by December 31, 2026, and the safest way to show that is a finished, furnished home with the listing open for bookings. If it slips into January, what happens depends on when your purchase contract became binding. For property acquired after January 19, 2025, you don’t lose the 100% bonus; the deduction simply moves to your 2027 return. For property under a binding contract on or before January 19, 2025, the stakes are real: 20% bonus if it’s in service in 2026, none on what that contract covers if it slips to 2027. The cost segregation study itself does not have to be done by December 31.

Every fall we hear some version of the same question: “We closed in September. Do we get the write-off this year?”

The honest answer is that the closing date doesn’t decide it. Neither does the date of your first booking. What decides it is a two-word tax concept that trips up a lot of new rental owners: placed in service.

What “placed in service” means

The Treasury regulations define it as the year the property is placed “in a condition or state of readiness and availability for a specifically assigned function.” IRS Publication 527, which covers rental property, puts it in plain English:

“You place property in service in a rental activity when it is ready and available for a specific use in that activity. Even if you aren’t using the property, it is in service when it is ready and available for its specific use.”

The IRS’s own examples make the point:

• A house is bought in April, repaired, and ready for rent on July 5. The owner starts advertising in July, and the first tenant moves in September 1. The house was placed in service in July, when it was ready and available, not in September.
• A property is listed for rent on October 1 and rented December 1. It was placed in service October 1.
• A dishwasher bought in November is delivered December 7 but isn’t installed until January 3. It wasn’t ready for use until January, so it was placed in service the next year.

So the rule cuts both ways. You don’t need a booking to be in service. But owning the property, or having the furniture sitting in boxes, isn’t enough either.

What “ready for guests” looks like for a short-term rental

For a short-term rental, the function the property is being readied for is hosting guests. Courts have consistently said a rental hasn’t started while it is still being repaired or renovated and hasn’t been offered for rent. In one Tax Court case, a house bought in August 2008 that still needed repairs and wasn’t rented until March 2009 was not placed in service in 2008.

Before December 31, the safest position is a property that is:

• Finished. Renovation and repair work complete, not “mostly done.”
• Furnished and stocked. Beds, linens, kitchen, everything a guest needs on night one.
• Permitted. If your city or county requires a short-term rental permit or registration, have it in hand. The IRS has taken the position that “approval of all required licenses and permits” is a factor in deciding when property is placed in service.
• Listed and bookable. The listing is live and the calendar is open. Being held out for rent is what courts look for.
• Documented. Screenshot the live listing with the date. Keep the permit, the final contractor invoice, and dated photos of the finished, furnished interior.

That last item matters more than people think. The IRS’s cost segregation audit guide specifically tells examiners to look for “incorrect placed-in-service dates.” If you’re ever asked, you want proof that the property was ready in 2026, not a recollection.

What happens if you miss December 31

This is where the One Big Beautiful Bill Act changed the stakes. In July 2025 it made 100% bonus depreciation permanent for property acquired after January 19, 2025. Before that, bonus was shrinking every year and missing a deadline cost you money. For most 2026 buyers, it now costs you time instead.

The date that matters is your acquisition date, which for a purchase is generally when a binding written contract became enforceable, after any contingencies and cancellation periods. It usually isn’t your closing date, but there’s an exception that can work in your favor: a contract that limits your damages to a deposit under 5% of the price may not count as binding, which can move your acquisition date later. If your contract was signed on or before January 19, 2025, have your CPA review it before assuming the old rules apply.

Your binding purchase contract	In service by Dec 31, 2026	In service in 2027
After January 19, 2025	100% bonus on your 2026 return	100% bonus on your 2027 return. The bonus isn’t lost, just pushed back a year.
On or before January 19, 2025	20% bonus on your 2026 return	No bonus on what that contract covers

The second row is where December 31 is a true deadline. Property acquired under a contract that became binding on or before January 19, 2025 stays on the old phase-down schedule. Under that schedule the rate is set by the year the property is placed in service, not the year you signed: 40% for 2025, 20% for 2026, and nothing after that. The IRS hasn’t released its 2026 forms yet, so confirm the rate with your CPA before filing.

This mostly affects long escrows, and some new construction, where the contract was signed in 2024 or early January 2025. For a home built for you under a contract signed before construction began, the date generally turns on when real construction work started, so a 2024 signature doesn’t automatically put you in this row. Your CPA can check it.

If you are in the second row, getting the property ready before year end is worth real money. One bright spot: furniture, appliances, and renovation work you bought or contracted for separately after January 19, 2025 have their own acquisition dates and can still qualify for 100% bonus. Your CPA can sort out which items fall on which side of the line.

For most owners in the first row, a one-year delay is still worth avoiding. A deduction on your 2026 return lowers the tax you pay next April. The same deduction on your 2027 return waits a full year longer. The big exception is a short-term rental owner who can’t realistically pass the tests in a few December weeks; see the traps below.

An example

Here is an illustration, not a client: a furnished short-term rental bought in 2026 for $1,100,000, with 20% of the price allocated to land. That leaves $880,000 of depreciable building and improvements.

A cost segregation study typically moves a meaningful share of a furnished short-term rental into 5-, 7-, and 15-year property: furniture, fixtures, appliances, finishes, landscaping, and site work. Using 32% (an assumption for this example; actual studies come in higher or lower), that’s $281,600 eligible for 100% bonus depreciation. The remaining $598,400 is depreciated over 39 years, which is how short-term rentals with average stays under 30 days are commonly treated, though no court or IRS ruling has settled it. Your CPA makes the final call on the recovery period.

	Ready in December 2026	Ready in January 2027
Depreciation on the 2026 return	about $282,200	$0
Depreciation on the 2027 return	about $15,300	about $296,300

Without a cost segregation study, the same property placed in service in December would produce about $940 of depreciation for 2026, because the building only gets half a month.

At a 35% federal tax rate, a $282,200 deduction is worth roughly $98,800, if the loss can offset your other income. Whether it can depends on the rules in the next section, and on a separate cap called the excess business loss limit, which limits how much business loss can offset wages and other income in a single year. A loss this size can hit that cap, especially on a single filer’s return, and a deduction this large usually spans more than one tax bracket. Your CPA can tell you what it’s actually worth to you. These figures are estimates for illustration; an actual study sets the real numbers.

The short-term rental timing traps

For many short-term rental owners, the whole point of cost segregation is the so-called STR loophole: if the average guest stay is seven days or less and you materially participate, the rental isn’t treated as a passive activity, and the depreciation can offset W-2 or business income. (Our guide to passive activity loss rules explains the full framework.)

Both of those tests are measured for the tax year. A December start squeezes them, and missing them has a long tail. If you fail either test for 2026, the bonus you claim that year is passive. Passing both tests in 2027 doesn’t send it back against your W-2 income; it generally waits for income from this rental, other passive income, or a sale. So for an owner counting on the short-term rental rules, a rushed December launch can turn out worse than a January launch with a full year to qualify. Have your CPA run both scenarios before you push.

The seven-day average is calculated from the stays in that year. If you go live on December 10, your 2026 average rests on a handful of December bookings, plus any stay that runs over New Year’s. If you’re listed but get no stays at all in 2026, there’s nothing to average, and we haven’t found IRS guidance or a court case on how that year is treated. Don’t count on the 2026 loss offsetting other income in that case until you’ve talked it through with your CPA.

Material participation has to happen in that year too. The most common test for short-term rentals is more than 100 hours and not less than anyone else, and that includes your cleaner and any property manager. With only a few weeks of operation, a cleaner’s hours can exceed yours fast. Whether hours you spend setting up the property before it’s available count toward the test is an open question; we’re not aware of any court case or IRS guidance that squarely decides it. Keep a detailed log from the day you buy, and talk to your CPA about how to treat it.

Watch your own use of the house. If you stay in the property personally this year for more than 14 days (or 10% of the days it’s rented, if greater), the tax code treats it as your residence for 2026. If it’s also rented for fewer than 15 days in total during 2026, the rental deductions are disallowed for the year, depreciation included. Rent it longer and your rental deductions are generally capped at your rental income, so the depreciation can’t create a loss against your other income that year; the excess carries forward. Buyers who vacation in a new house over the summer and list it in December are the ones who get caught.

If your average stay is longer than seven days, or you won’t materially participate, the depreciation is still real but is generally passive. It offsets passive income now and carries forward until it can be used. For owners in that position, a one-year slip into 2027 usually costs less.

The study can wait. The property can’t.

Here’s the good news: nothing requires your cost segregation study to be finished by December 31. What has to happen by year end is the property being ready and available. The study only has to be done in time for your CPA to file the 2026 return, which for an individual owner is April 15, 2027, or October 15, 2027 with an extension (March 15, 2027, or September 15 with an extension, if the rental is held in a partnership or S corporation).

And if you file without one, the benefit isn’t gone. If the study is done before your 2027 return is filed, your CPA can generally amend the 2026 return. After that, it comes through a catch-up adjustment on Form 3115, which we explain in cost segregation on a property you already own. A catch-up lands in the later year, so whether it offsets W-2 income depends on whether you pass the short-term rental tests in that year.

What you can’t fix that way is the placed-in-service date itself. The regulations say a change in placed-in-service date “is not treated as a change in method of accounting,” so getting it wrong is fixed by amending returns or adjusting later ones, not with a simple catch-up form. Get the date right, and document it, the first time.

Before December 31: a checklist

1. Find your contract date. Check when your purchase contract became binding. If it was on or before January 19, 2025, treat December 31 as a hard deadline.
2. Decide with your CPA whether to push. If you’re counting on the short-term rental rules, compare a December launch with a January one before you rush.
3. Finish the work. Repairs, renovation, and furnishing complete.
4. Get the permit if your city or county requires one.
5. Go live. Listing published, calendar open.
6. Screenshot and save everything with dates.
7. Start your hours log now, and know how many hours your cleaner and manager are logging.
8. Don’t use the property personally in ways that could trigger the personal-use rules.
9. Line up the cost segregation study. It can be done after year end, but starting early gives your CPA time.

Where we come in

We prepare the engineering-based cost segregation study your CPA uses to claim the deduction. If you bought a rental this year, we can give you a free estimate of what the study would reclassify, so you and your CPA can decide whether getting the property ready before December 31 is worth the push. Start with our cost segregation study overview, see what a study costs, or book a free consultation.

This article explains federal tax rules in general terms. It is not tax advice. Your CPA decides when your property was placed in service and how to report it. State rules can differ, and many states don’t follow federal bonus depreciation; see bonus depreciation by state.