Placed in Service by December 31: The Date That Decides Your Cost Segregation Deduction

With about two months left in 2026, real estate investors keep asking the same question: "If I close before December 31, do I get the 2026 deduction?" The answer is a qualified maybe. Depreciation, including the 100% bonus depreciation that makes cost segregation so valuable, starts on the placed-in-service date. That date is often different from your closing date, and it decides which tax year gets the deduction.

This guide explains what the term means for rental property, how it interacts with the mid-month convention and bonus depreciation, what paperwork to keep, and what your options are if the date slips into 2027.

What "Placed in Service" Means for a Rental

Property is placed in service when it is ready and available for its intended use. For a rental, that generally means:

The property is finished and in rentable condition.
It's available for rent, which usually means listed or otherwise offered to tenants.

Notice what's missing from that list: a signed lease and a paying tenant. You typically don't need a tenant in place. You need a property that is ready to rent and on the market. Your CPA makes the final call, but that's the standard they'll apply.

Closing Date vs. Placed-in-Service Date

Buying a property and placing it in service are two separate events. Sometimes they happen the same day, and sometimes months apart.

Scenario	Likely placed-in-service date
Turnkey rental, closed December 12, listed for rent December 14	December 2026
Closed December 12, but needs a 10-week renovation before it's rentable	After the work is done, likely 2027
Closed in October, listed in November after cleaning and minor repairs	When it became rent-ready and available
Closed in October, then held off the market for personal use	Not placed in service until you actually offer it for rent

The common trap is the Q4 purchase that needs work. Closing on December 28 doesn't help if the building isn't habitable until March. As we noted in our year-end planning checklist, closing before year-end doesn't guarantee a 2026 deduction. Being ready to rent before year-end is what counts.

Renovations can also be split. If you buy a multi-unit building and some units are rent-ready while others are under renovation, your CPA may treat the ready units as placed in service while the others wait. The facts for each unit matter.

How the Mid-Month Convention Works

Residential rental property (27.5-year) and nonresidential real property (39-year) both use the mid-month convention. No matter what day of the month the property is placed in service, the IRS treats it as placed in service at the midpoint of that month.

Two practical consequences:

The day within the month doesn't matter for the building. Placed in service December 2 or December 29 gives you the same first-year percentage for the building.

A December date yields a very small first-year amount on the building itself. The first-year IRS rate for residential property placed in service in December is 0.152%. For nonresidential property in December it's 0.107%.

On a $720,000 residential building basis, that's about $1,094 of first-year straight-line depreciation. This is why the study matters so much for a late-year placement. The reclassified 5-, 7-, and 15-year components are where the first-year deduction comes from, not the building.

Why the Date Matters for Bonus Depreciation

Bonus depreciation applies in the tax year the property is placed in service. Under the One Big Beautiful Bill Act (OBBBA), 100% bonus depreciation is permanent for qualifying property acquired after January 19, 2025, so there's no shrinking percentage to chase. We cover the details in our guide to 100% bonus depreciation in 2026.

What the placed-in-service date controls is which return gets the deduction:

Placed in service by December 31, 2026: reclassified short-life components are eligible for 100% bonus on your 2026 return.
Placed in service January 1, 2027 or later: the same deduction goes on your 2027 return.

A few points that stay the same under the restored rules:

The building itself (27.5- or 39-year property) doesn't qualify for bonus. Only reclassified short-life components do.
Land is never depreciable.
A binding contract on or before January 19, 2025 can change the applicable rate, so confirm your contract date, not just your closing date.

Missing the date doesn't forfeit the deduction under a permanent 100% rate. It moves it one year later. The cost is time value, plus any 2026 tax savings you were counting on.

Short-Term Rentals

Short-term rentals follow the same basic rule: the property is placed in service when it's ready and available to rent. For an Airbnb or VRBO property, that usually means furnished, cleaned, photographed, and live on the booking platform. A property that's closed on but still waiting on furniture isn't ready for guests.

Furnishings are a good example of why timing matters twice. Furniture and appliances that you buy and place in service are generally short-life property that a study can capture, but they also need to be in the property and in use for rental, not sitting in a delivery warehouse, by year-end.

Short-term rentals with an average guest stay of seven days or less can also be treated as non-passive if you materially participate, which can change whether a big first-year deduction is usable. See our guide to cost segregation for Airbnb and short-term rentals for the details. Your CPA should confirm the classification and recovery period for your specific property.

Document the Date

If the IRS ever questions your placed-in-service date, you'll want evidence created at the time, not reconstructed later. Keep:

Closing statement showing the purchase date and costs.
Certificate of occupancy or final inspection sign-off, if there was construction or renovation.
Contractor invoices and completion dates for any work done before rent-ready status.
Listing records, such as dated screenshots, listing confirmations, or property management agreements.
Lease agreements or booking records showing when rental activity began.
Utility activation dates and insurance effective dates for the rental use.
A short dated note from you or your property manager stating when the unit became available.

Hand this package to your CPA along with your cost segregation report. The report classifies the components, and your records support the date those components started depreciating.

What If You Miss December 31?

Say the renovation runs long or the listing goes live January 3. You haven't lost the deduction. You have a few options, and your CPA will help you pick one.

1. Accept the 2027 placement. With 100% bonus depreciation permanent, the study's first-year deduction simply lands on your 2027 return. You can still commission the study now so it's ready. 2. Speed up what's genuinely within your control. If the property is a few days from being ready, finishing and listing it by December 31 may move the date into 2026. This only works if the property is truly ready, not if you're simply posting a listing for a unit that can't be rented. Don't backdate anything. 3. Use a look-back study and Form 3115 for property already in service. If you placed a property in service in a prior year, or in 2026 and file the return without a study, you can claim the missed depreciation later. A look-back study reclassifies components, and Form 3115 changes your depreciation method so the catch-up lands as a Section 481(a) adjustment on a later return, with no amended returns. Our look-back cost segregation guide walks through a worked example and the filing steps. Note that the 3115 path is for property that is already in service. It can't move a placed-in-service date.

Your Quick Checklist

List every property you bought or renovated this year and its status: rent-ready, listed, or still in progress.

Set an internal deadline well before December 31 for finishing work and getting each property live.

Collect documentation as you go, not in March.

Confirm your bonus rate, including the contract date if you signed early in 2025.

Check your income and passive loss position so you know whether the deduction is usable in 2026.

Commission the study so the report is ready when your preparer needs it.

Frequently Asked Questions

Does closing before December 31 mean the property is placed in service in 2026?

Not necessarily. Closing transfers ownership. Placed in service requires the property to be ready and available for rent. A turnkey property you list right after closing can qualify. A property that needs weeks of renovation generally doesn't until the work is done.

Do I need a tenant by December 31?

Generally no. The standard is that the property is ready and available for rent, not that it's occupied. Keep records showing when it was listed or offered to tenants, and confirm the date with your CPA.

Does the day of the month matter for the building's depreciation?

No. The mid-month convention treats residential and nonresidential real property as placed in service at the midpoint of the month, so December 3 and December 29 produce the same first-year percentage for the building.

Does the cost segregation study have to be finished by December 31?

No. The property has to be placed in service by December 31. The study needs to be ready before your preparer finalizes the 2026 return. See our year-end planning guide for the timeline.

Can I still get 100% bonus depreciation if the property slips into 2027?

Under current law, 100% bonus is permanent for qualifying property acquired after January 19, 2025, so the deduction would apply to 2027 instead of 2026. Your CPA can confirm eligibility based on your acquisition and contract dates.

Can Form 3115 fix a late placed-in-service date?

No. Form 3115 changes your depreciation method for property that is already in service, which lets you recover missed depreciation. It doesn't change the date a property was placed in service.

The Bottom Line

December 31 is a placed-in-service deadline, not a closing deadline. Property that is ready and available for rent by that date puts its reclassified short-life components on your 2026 return. Property that isn't waits a year. Check each property's status now, document the date, and get your study started so the numbers are ready when your CPA needs them. If a date slips, you still have the 2027 return, and if you have property already in service without a study, the look-back path remains open.

This article is general education, not tax advice. Placed-in-service dates, bonus eligibility, passive loss rules, and state conformity all depend on your facts, so talk to your CPA before you act on any of it.

ROOM42 prepares engineering-based cost segregation studies for residential and commercial investors, including look-back studies for properties you already own. Get your free estimate with no credit card required.