September 7, 2026 · 4 min read
I bought my rental five years ago. Can I still do a cost segregation study?
This is the question we hear most often, usually with an apologetic tone attached, as though being late disqualifies you. It does not. A cost segregation study is not something that has to be done in the year you buy a property.
If you have owned a rental for five years and have been depreciating it the ordinary way over 27½ years, you have been taking a smaller deduction each year than a study might have supported. The tax code has a mechanism for exactly this situation, and it is routine enough that your accountant will have handled it before.
What catching up involves
Changing how you depreciate a property is treated as a change in accounting method. Your accountant files a form for it — Form 3115 — and the cumulative difference between what you did claim and what you could have claimed is worked out and brought into the current year, rather than requiring you to amend every prior return one at a time.
That last part is the bit worth understanding, because people assume the alternative. You are generally not going back and reopening five years of filed returns. There is a mechanism designed to avoid that.
What being late does change
One practical thing. A study describes the property as it was when you placed it in service. If you have replaced the kitchen since you bought the place, the property you film today is not quite the property you bought, and that difference matters to the study.
It is not a problem so much as something to be honest about. If you have renovated, say so and keep the invoices — a documented cost for work you actually paid for is better evidence than an estimate of what something similar would cost. If you have not renovated, the property in front of the camera is the property that was bought, and the job is simpler.
Is there a point where it is too late?
The obvious one is selling. Once a property is gone, the question stops being about depreciation going forward and becomes a question about the sale itself — and that is squarely your accountant’s territory rather than ours. If a sale is anywhere on your horizon, raise it with them before you commission a study of any kind.