Congress set up thousands of Opportunity Zones in 2017, mostly in lower-income areas, to pull investment into those neighborhoods. If you have a gain from selling almost anything, you can put that gain into a Qualified Opportunity Fund, or QOF, within 180 days and put off paying tax on it.
The fund then has to put that money to work inside the zone, usually by buying property and fixing it up. That fix-up requirement is where cost segregation comes in, and it is also where owners most often trip up.
The big idea: cost segregation cannot get you the opportunity zone tax break by itself. What it can do is give you a clean, dated record of your improvement spending, and speed up the depreciation on the dollars you put into the building.
The substantial improvement test
If your fund buys a building that is already standing, the law does not let you just hold it. Within 30 months of buying it, you have to spend more than the building's own basis on improvements. This is the substantial improvement test (IRC §1400Z-2(d)(2)(D)).
One detail trips people up: the test looks at the building, not the land under it. In Rev. Rul. 2018-29, the IRS said the basis that belongs to the land is not counted when you measure whether the building was substantially improved. For example, say you buy a property for$600,000, and the county records show$150,000 of that as land value and$450,000 as the building. You would need to spend more than $450,000 on improvements within 30 months, not $600,000. That land carve-out matters, and it is easy to miss without a clear breakdown of the purchase price.
Why cost segregation helps here
A cost segregation study does two separate jobs on an opportunity zone project, and it is worth keeping them straight:
- It documents the spend. A study gives you an itemized, dated record of what you spent on the building and when. That is exactly the kind of evidence that supports the substantial improvement test if the IRS ever asks how you got there.
- It speeds up depreciation on the improvement dollars.Once the improvement money is spent, those same dollars can be sorted into 5, 7, and 15-year parts, the same way any other renovation would be. That is a real, separate tax benefit on top of the opportunity zone deferral itself.
A study will not qualify your project on its own. It can prove you met the test, and pay for itself again on the improvement dollars.
The deadline already on the clock: December 31, 2026
If you already put a gain into a QOF investment in an earlier year, the law only lets you defer that gain until a fixed date: the earlier of the date you sell the fund investment, or December 31, 2026 (IRC §1400Z-2(b)(1)). That date arrives whether or not you have sold anything. If you have money sitting in a fund from a prior year, talk to your tax advisor now about how that gain lands on your return.
What changed for new investments
The One Big Beautiful Bill Act renewed the opportunity zone program for new investments, with a new round of zone designations starting in 2027 and its own rules for that round. If you are weighing a brand-new opportunity zone investment under the new rules rather than an older one already in a fund, ask your tax advisor how the new terms apply to your timeline. This is a newer, still-settling part of the law, and the exact mechanics are your tax advisor's call, not ours.
One more fork in the road: 1031 or opportunity zone?
When you sell appreciated property, a 1031 exchange and an opportunity zone investment are two different ways to defer the same gain, and you generally pick one path for a given dollar of gain, not both.See how a 1031 exchange changes your depreciation instead.
This election belongs to your tax advisor
Choosing to invest in a QOF, making the deferral election, and reporting it on your return are decisions for you and your tax professional. We are not the ones who make that call. Our part starts once the building is bought and the improvement dollars are being spent: an engineering-based study that documents the work and finds the parts that depreciate faster.
Next step:See your savings range in seconds for the improvement dollars you have already spent, or readwhat is cost segregation? for the basics.
This guide explains general tax ideas in plain words. It is not tax advice for your situation, and it is not investment advice about any fund. Opportunity zone rules turn on exact dates, entity structure, and how the fund itself is organized. Your study and tax positions are reviewed by a licensed tax professional. Always confirm the plan, including the QOF election itself, with your own advisor before you file.