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Property is generally placed in service when it is ready and available for its assigned use, not when you closed on it, not when you paid for it, and not when a tenant moves in. That date controls when depreciation begins, which tax year the deduction lands in, and, under current law, which bonus depreciation rate applies. Because the One Big Beautiful Bill Act ties 100 percent bonus depreciation to property placed in service after January 19, 2025, the placed-in-service date is now one of the most financially significant dates on your file.
A couple in Bismarck, North Dakota closed on a small retail strip in late July. The prior tenant had gutted the space on the way out. The building needed electrical work, a new storefront, and a certificate of occupancy before anyone could use it. That work finished in December. The first tenant signed in February of the following year.
Three dates, three different years in play. When did depreciation start?
Their bookkeeper used the July closing date, because that is when they bought it. That was wrong, and it put a full year of depreciation in a year it did not belong. Their CPA caught it, but not before it had been filed that way, and unwinding it cost more than getting it right would have.
The placed-in-service date is one of those concepts that sounds obvious until you have a property that does not cooperate. This article explains what the standard actually is, why the date is worth more money now than it has been in years, and where people get it wrong.
The general rule is that property is placed in service when it is in a condition or state of readiness and availability for a specifically assigned function. In plain terms: when it is ready to do the job you bought it to do.
Two things follow from that, and both surprise people.
First, you do not have to actually be using it. A building that is ready for occupancy is generally placed in service even if no tenant has moved in yet. Readiness is the test, not use. An apartment building that has passed inspection and is available to rent is generally placed in service, even if the first lease is signed weeks later.
Second, buying it is not enough. Acquiring a property that is not yet ready for its intended use does not start the clock. The Bismarck strip was purchased in July but was not in a condition of readiness until the work was done and it could lawfully be occupied. The purchase date and the placed-in-service date were months and a tax year apart.
The specifically assigned function language matters too. The question is readiness for the use you intend, in the business you are conducting. A building you intend to operate as a medical clinic and a building you intend to warehouse pallets in may reach readiness at different points, because the assigned function differs.
The placed-in-service date has always determined when depreciation begins. What changed is how much rides on it.
The One Big Beautiful Bill Act, signed into law on July 4, 2025, permanently restored 100 percent bonus depreciation for qualifying property acquired and placed in service after January 19, 2025. Property that falls on the wrong side of that cutoff is governed by the prior phase-down schedule, under which bonus had dropped to 40 percent for 2025.
That is a very large swing on the same building. Consider a property where a cost segregation study identifies $600,000 of components qualifying for shorter recovery periods. On the favorable side of the cutoff with 100 percent bonus, that is a $600,000 first-year deduction. On the other side at 40 percent, the first-year bonus piece is $240,000, with the balance recovering over the components' normal schedules. Same building, same study, same components. The date decided the outcome.
Worth noting alongside this: the acquisition date matters too, and it is a separate test. IRS Notice 2026-11 confirmed that the long-standing written binding contract rule continues to apply, meaning your acquisition date can be the date you signed a binding contract rather than the date you closed. Both the acquisition date and the placed-in-service date need to clear the cutoff for the full benefit. That interaction is its own topic, and it catches people who assume the closing date settles everything.
Some properties make the determination easy. A finished building you buy and immediately lease is not a puzzle. Others are harder, and these are the situations where getting advice early pays.
New construction. A building under construction is not placed in service until it reaches readiness for its assigned use, which typically involves completion and the ability to lawfully occupy. Certificates of occupancy are commonly part of the analysis, though the legal standard is readiness rather than any single document. On a project that finishes near year end, the difference of a few weeks can move the entire deduction into a different tax year.
Renovation of an acquired property. The Bismarck situation. If a property cannot serve its intended function until substantial work is completed, the purchase date is not the placed-in-service date. Where the property could have been used but you chose to improve it first, the analysis can differ. The facts drive it.
Phased projects. A property completed and occupied in stages, like a multi-building community or a retail center delivering suites over time, may have components reaching readiness at different points. Portions may be placed in service before the entire project is finished. This is fact-intensive and worth planning around rather than reconstructing later.
Property idle after readiness. Property that is ready and available but temporarily idle is generally still treated as placed in service. Readiness governs, not activity. A vacant but rent-ready unit is a different case from a unit that cannot be occupied.
Seasonal or intermittent use. Property ready for its assigned function but used only part of the year is generally placed in service when it becomes ready, not when the season starts.
Once the placed-in-service date is established, depreciation conventions determine how much of the first year's depreciation you actually claim. This is mechanical, and the details deserve a word with your CPA, but the shape is worth knowing.
Real property, meaning residential rental and nonresidential real property, uses a mid-month convention. Property is treated as placed in service in the middle of the month it was actually placed in service, so the month matters but the specific day generally does not.
Personal property with shorter recovery periods generally uses a half-year convention, treating property as placed in service at the midpoint of the year. There is an exception: where a large enough share of the year's personal property additions falls in the final quarter, a mid-quarter convention can apply instead, computing depreciation from the midpoint of the quarter each item was placed in service. The threshold test and the precise basis computation are technical, and whether it applies to your year is a determination for your CPA.
One practical note that has changed the stakes here. When 100 percent bonus depreciation applies to qualifying property, the entire cost of that property is generally deducted in the first year regardless of convention, so the convention question matters far less for bonus-eligible property than it did during the phase-down years. It still matters for property that is not bonus eligible, for taxpayers who elect out of bonus, and for property under the alternative depreciation system. Ask your CPA whether it affects your specific situation rather than assuming it does or does not.
The placed-in-service date is the hinge the entire study swings on.
It determines the tax year the accelerated deductions land in. It determines the bonus depreciation rate applied to reclassified components. On a phased or renovated property, it can determine whether portions of the property are analyzed together or separately. A cost segregation study built on the wrong placed-in-service date produces the right components and the wrong result.
This is one of the reasons an engineered study asks for documentation rather than just a purchase price. Certificates of occupancy, construction completion records, permit history, and lease commencement information all inform the analysis. A software model that takes your closing date at face value and runs will happily give you a number built on a date that does not hold.
Keith Cunningham's framing applies. The Bismarck couple did not make an arithmetic error. They made a definitional error, which is worse, because arithmetic errors get caught and definitional errors get filed. The number was computed correctly off a premise that was wrong from the start.
Using the closing date. The most frequent error. Purchase and readiness are different events and can fall in different tax years.
Waiting for a tenant. Readiness is the standard, not occupancy. A rent-ready building is generally placed in service even while vacant.
Assuming the certificate of occupancy is the whole answer. It is commonly relevant evidence, but the legal standard is readiness for the assigned use, and the analysis considers the facts as a whole.
Ignoring the acquisition date. Under the binding contract rule confirmed in Notice 2026-11, your acquisition date can be your signing date. Both dates matter for the current bonus rules.
Treating a phased project as one date. Portions of a project may reach readiness at different times, and forcing a single date can misstate the result in both directions.
Reconstructing the date after filing. The documentation that supports the date is easiest to assemble while the project is happening. Going back three years later to prove readiness is far harder.
If you are buying, building, or renovating, treat the placed-in-service date as a planning item rather than a bookkeeping detail. On a project finishing near year end, a short acceleration or delay can move a large deduction between tax years, and the difference is worth knowing before you decide the schedule.
Keep the documentation as you go. Permits, inspections, certificates of occupancy, contractor completion records, and lease information are what support the date if it is ever questioned.
And get the date right before the study is built on it. The Cost Seg America team works with property owners and their CPAs to establish and document the placed-in-service date correctly, then builds the engineered component analysis on that foundation. More than 16,000 studies completed, more than 125 IRS audits defended with zero losses and zero dollars ever returned to the IRS. Engineered, not estimated.
Request a free proposal, or reach out to the Cost Seg America team directly:
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What does placed in service mean?
Property is generally placed in service when it is in a condition or state of readiness and availability for a specifically assigned function. It is about readiness for the intended use, not about when you bought it or when you started using it.
Is the placed-in-service date the same as my closing date?
Often not. If the property was not ready for its intended use when you closed, for example because it required renovation or completion before it could be occupied, the placed-in-service date is later and can fall in a different tax year.
Does a building have to be occupied to be placed in service?
Generally no. A building that is ready and available for its assigned use is typically placed in service even if it is vacant. Readiness governs rather than actual occupancy.
Why does the date matter so much right now?
Because the One Big Beautiful Bill Act ties 100 percent bonus depreciation to qualifying property placed in service after January 19, 2025. Property on the other side of that cutoff falls under the prior phase-down rates, which is a large difference on the same building.
What about a building under construction?
It is generally not placed in service until it reaches readiness for its assigned use, which typically involves completion and the ability to lawfully occupy. On projects finishing near year end, timing can move the deduction between tax years.
Does the acquisition date matter too?
Yes, separately. IRS Notice 2026-11 confirmed the written binding contract rule, under which your acquisition date can be your contract signing date rather than your closing date. Both dates factor into current bonus depreciation eligibility.
Who determines the date for my property?
It is a factual determination made with your CPA, supported by documentation such as permits, inspections, certificates of occupancy, and completion records. The Cost Seg America team works with owners and their CPAs to establish and document it before the study is built.
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