What Is the Substantial-Improvement Test for an Existing Opportunity Zone Building?
An existing building a Qualified Opportunity Fund buys is substantially improved if, during any 30-month period after acquisition, additions to its basis exceed its adjusted basis at the start of that period (IRC §1400Z-2(d)(2)(D)(ii)); land is excluded, so the land-and-building allocation documented in a cost segregation study supports the building basis the fund has to exceed.
The property does not earn Opportunity Zone benefits automatically: unless the building was vacant long enough to count as original-use property, the fund generally must substantially improve it. In plain terms: over 30 months you generally have to invest more than the building was worth when you bought it. The key word is building — the test is measured against the basis of the structure, not the land underneath it. Land is excluded from the substantial-improvement calculation (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iv)(A) and (E)). That single fact is where cost segregation enters.
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Why Does the Land and Building Allocation Set the Bar?
The lower your building basis, the lower the dollar amount you must exceed to pass the test. Consider a $5,000,000 Opportunity Zone acquisition:
- Generic 80/20 assumption: $4,000,000 building / $1,000,000 land. You must add more than $4,000,000 in improvements within 30 months.
- Supported allocation after analysis: say the land is worth more than the rule-of-thumb suggests — $3,200,000 building / $1,800,000 land. Now you must exceed only $3,200,000.
An $800,000 difference in the bar you have to clear can decide whether a renovation budget qualifies the project at all. Opportunity Zone cost segregation — a study that separates land, 15-year land improvements, the structural shell and short-life components from source documents — provides the support for a documented building-versus-land allocation rather than a guess. The regulation measures the improvement by additions to the basis of the building and does not say whether reclassifying 5-, 7- or 15-year components changes the starting basis, so do not assume reclassification lowers the threshold; confirm with your advisor.
How Is the Land-Versus-Building Split Determined for Cost Segregation and the Opportunity Zone Substantial-Improvement Test?
When land and a building are bought together for one price, the land-versus-building split is determined by dividing that price in proportion to the fair market values of the land and the depreciable property at acquisition (Treas. Reg. §1.167(a)-5), and the result is the depreciable basis a cost segregation study reclassifies. The same building basis is the one the Opportunity Zone substantial-improvement test is measured against, because the test uses the purchased building’s basis as determined under §1012 (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iv)(A)) and the substantial-improvement rules in Treas. Reg. §1.1400Z2(d)-2(b)(4) set no separate allocation method. Four methods are used to support the split, and each is only as good as the documents behind it.
The purchase agreement allocation. When the purchase is an applicable asset acquisition under IRC §1060 (a group of assets that makes up a trade or business, such as an operating hotel), a written allocation the buyer and seller agreed generally binds both of them under §1060(a) unless the IRS determines it is not appropriate, and the IRS Cost Segregation Audit Techniques Guide (Publication 5653) says a later cost segregation study cannot change an allocation between personal and real property made that way. The House report on that rule, quoted in the guide, says the IRS may still challenge an agreed allocation, particularly where the buyer and seller had no opposing tax interests (H. Rept. 101-881). For a purchase outside §1060, the guide says it is unclear whether the same result applies, so an allocation stated in the purchase agreement is a starting point that needs support from fair market values at acquisition rather than a figure to rely on alone. The supporting documents are the purchase agreement and the closing statement, which shows the price and the acquisition costs added to basis. When §1060 applies, both parties also report the allocation on Form 8594; the residual method and the Peco Foods case are covered in purchase price allocation for real estate.
The county assessor’s land-to-improvement ratio. The assessor’s ratio applies the assessed land value’s share of the total assessed value to the purchase price: for example, a $5,000,000 purchase of a parcel assessed at 30 percent land and 70 percent improvements would allocate $1,500,000 to land and $3,500,000 to the improvements. It is simple to document from the assessor record for the year of acquisition, but an assessment is made for property tax, on the assessor’s schedule and methods rather than at the purchase date, and the Cost Segregation Audit Techniques Guide tells the IRS to be wary of a study that relies solely on local assessed values rather than determining fair market value.
An appraisal. An appraisal as of the acquisition date that values the land first, at its highest and best use as though vacant, and the improvements separately is the method the Cost Segregation Audit Techniques Guide describes, and the guide expects any value relied on to be developed under professional appraisal standards (typically USPAP) by a competent and qualified appraiser. Its limits are its date and its scope: an appraisal dated well before or after the purchase does not show value at acquisition, and one that reports a single value for the whole property does not supply the split.
A cost approach. A cost approach estimates what it would cost to replace the building, less physical deterioration and functional and economic obsolescence, and it fits beside a land value determined directly, since the guide has the land valued first. It is not a way to find the land value: subtracting a building estimate from the price leaves land as the residual, which the Cost Segregation Audit Techniques Guide calls inappropriate because it may understate the land and overstate the depreciable improvements. For a building the fund constructs on land it bought separately, there is no lump sum to divide: the land’s cost is its purchase price, and the building’s cost comes from the construction contracts, pay applications and invoices.
A fixed rule-of-thumb ratio, such as the 80/20 split in the example above, does not measure this property’s land, so it is a placeholder until one of these methods replaces it. When the documents support less land than the rule of thumb assumes, the supported building basis, and with it the amount the fund’s improvements must exceed, comes out higher, not lower.
| Document | What it supports |
|---|---|
| Closing (settlement) statement | The total cost being divided: the price plus the acquisition costs added to basis |
| Purchase agreement | Any allocation the buyer and seller agreed, and whether the purchase included an operating business |
| County assessor record | The assessed land and improvement values for the year of acquisition |
| Appraisal | Separate land and improvement values as of the acquisition date |
| Construction pay applications (AIA G702/G703) and invoices | The cost of a building the fund constructs, and the improvement costs incurred during the 30-month period |
| Trial balance | How the fund’s books carry land, building and improvements, the figures a cost segregation study’s total is reconciled to |
Why the split matters twice. First, land is not depreciable: depreciation under §167 and §168 applies only to property subject to wear and tear, and Treas. Reg. §1.167(a)-2 says the allowance does not apply to land apart from the improvements added to it. A dollar allocated to the land itself (as distinct from 15-year land improvements such as paving and landscaping) is therefore never reclassified by a cost segregation study, and it is recovered only through basis when the land is sold or otherwise disposed of.
Second, land is outside the substantial-improvement measurement: when a fund or its qualified opportunity zone business purchases a building on land in a qualified opportunity zone, the improvement is measured by its additions to the basis of the building, as determined under §1012, and the land under the building need not be separately improved (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iv)(A) and (E)). Under IRC §1400Z-2(d)(2)(D)(ii), the additions during the 30-month period must exceed the building’s adjusted basis at the start of that period, or 50 percent of it for property in a qualified opportunity zone comprised entirely of a rural area.
The regulation’s own example is an asset purchase of a hotel business for $5 million, with $1 million allocated to land and $4 million to the building, furniture and fixtures; because the basis allocated to the hotel was $4 million, the example concludes the fund must expend $4 million to improve the hotel within the 30-month period (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iii)(D)(1), Example 1). The example takes that allocation as given and does not show how it was determined.
The two effects pull in opposite directions: for a given total price, every dollar allocated to land reduces the amount the fund’s improvements must exceed and is a dollar that cannot be depreciated, so the split follows the land’s fair market value at acquisition, not whichever result either rule would favour.
A cost segregation study does not lower the substantial-improvement threshold. The threshold is the building’s adjusted basis at the start of the 30-month period; a cost segregation study supports the documented land and building allocation and records the improvement costs, and the regulation does not say whether reclassifying 5-, 7- or 15-year components changes that starting basis, so reclassification should not be assumed to lower it. A ClickDrag Finance Opportunity Zone cost segregation study does not appraise the land: it takes the land figure from the documents provided, such as the closing statement, purchase agreement, appraisal or trial balance, where they state one, and reconciles the land, building and component amounts to the total cost. Whether the substantial-improvement test is met, and which allocation the fund relies on, is a determination for the fund’s tax counsel.
What Does One Cost Segregation Study Do on an Opportunity Zone Deal?
One document-driven, human-reviewed cost segregation study documents the land and building split the substantial-improvement test is measured against and also produces the depreciation schedule you will use for the next decade. That is the efficiency of running it early on an OZ deal:
- Qualification support. A documented land/building split helps establish the substantial-improvement threshold and supports the position if questioned — and where the scope is still on the drawing board, the A/E team can separate land, shell, qualified improvement property, site work and equipment inside the substantial-improvement scope itself.
- Accelerated depreciation. The improvements you make to pass the test are themselves full of 5-, 7-, and 15-year property — reclassified by the study and, for qualifying property, eligible for 100% bonus depreciation under §168(k) when the property is acquired after January 19, 2025 (for a contractor or partner taking equity in the project rather than cash, see how general-contractor equity affects cost segregation deductions).
- Component records for exit. Held 10+ years, an investor who sells the qualifying fund interest and makes the IRC §1400Z-2(c) election to treat basis as fair market value excludes the gain on that interest — including the depreciation recapture the study front-loaded — so the acceleration becomes permanent. The component schedule is the ledger that documents it.
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Did OZ 2.0 Lower the Substantial-Improvement Bar for Rural Property?
Under the 2025 One Big Beautiful Bill Act, for property in a qualified opportunity zone comprised entirely of a rural area, the improvement amount is 50 percent of adjusted basis rather than 100 percent (IRC §1400Z-2(d)(2)(D)(ii), effective July 4, 2025); separately, a Qualified Rural Opportunity Fund gets a 30 percent five-year basis step-up for investments made after December 31, 2026. The 50 percent amount for property in a qualified opportunity zone comprised entirely of a rural area follows the property and its zone, not the fund’s status. Pair it with a documented land and building allocation and a value-add rural project can clear qualification with a far smaller relative improvement spend. For rural sponsors, the allocation work matters even more, because every dollar a supported allocation assigns to land rather than to the building lowers an already-lower bar.
When Does the Allocation Work Start on an Opportunity Zone Acquisition?
Because the test runs on a 30-month clock that starts at acquisition, the time to think about allocation and component classification is at the front of the deal, not at the first tax filing — the windows that follow are laid out in a timing playbook for cost segregation in an Opportunity Zone deal. Getting the study underway early means the land/building split is supported before improvement spending is planned, the same spending a fund’s QOZB working-capital safe harbor plan has to schedule in writing, and the depreciation schedule is ready the moment the property is placed in service.
The Takeaway
On an Opportunity Zone project involving an existing building, the substantial-improvement test is usually the gate — and your land-versus-building allocation is the combination that opens it. A cost segregation study supports that allocation, classifies the improvements for accelerated and bonus depreciation, and leaves you with the component records that make the 10-year exit clean. It is the same study, doing three jobs. For the full picture of why the OZ structure makes cost segregation a permanent benefit rather than a timing one, see our companion piece, Cost Segregation + Opportunity Zones 2.0. Coordinate the allocation, the election and the improvement plan with your tax advisor.
Acquiring in a zone this year? Start the study at acquisition so the allocation is in place before your 30-month clock burns down.
Where the allocation needs the land and building appraised, Ellaval is ClickDrag Finance’s preferred vendor for valuation services — the entity to approach for fair market value valuations prepared for tax purposes, including estate and gift planning, impact fund investments and Opportunity Zone deals, working with CPAs and high-net-worth individuals. Reach Howard Krieger at howard@ellavoz.com.
Frequently Asked Questions
What is the substantial-improvement test for an Opportunity Zone property?
Property is substantially improved if, during any 30-month period after acquisition, additions to the basis of the property exceed the adjusted basis of the property at the start of that period — the framework of IRC §1400Z-2(d)(2)(D). Unless the building was vacant long enough to count as original-use property, a Qualified Opportunity Fund buying an existing building generally must meet that test. For property in a qualified opportunity zone comprised entirely of a rural area, the improvement amount is 50 percent of adjusted basis rather than 100 percent (IRC §1400Z-2(d)(2)(D)(ii), effective July 4, 2025), and that follows the property and its zone rather than the fund’s status.
Does the substantial-improvement test include the land?
No — the test is measured against the basis of the structure, not the land underneath it, so land is excluded from the substantial-improvement calculation. That is why the land-versus-building allocation decides the dollar figure you have to exceed: on a $5,000,000 acquisition, a $4,000,000 building basis means adding more than $4,000,000 within 30 months, while a supported $3,200,000 building basis means exceeding only $3,200,000.
How does a cost segregation study affect the substantial-improvement bar?
According to ClickDrag Finance's guide to the Opportunity Zone substantial-improvement test, a cost segregation study documents the land and building allocation the test is measured against, instead of a rule-of-thumb split: the test is measured against the adjusted basis of the building, with land excluded (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iv)(A) and (E)). A cost segregation study separates land from the depreciable improvements using source documents, which is what supports the building basis that sets the threshold; reclassifying the building’s 5-, 7- and 15-year components changes the depreciation schedule and should not be assumed to lower the threshold. In the $5,000,000 example above, the gap between a generic 80/20 assumption and a supported allocation was $800,000 of required improvement spend.
How is the land and building split determined for an Opportunity Zone cost segregation study?
When land and a building are bought for one price, the split divides that price between them in proportion to their fair market values at acquisition (Treas. Reg. §1.167(a)-5), supported by the purchase agreement’s allocation, the county assessor’s land-to-improvement ratio, an appraisal that values the land at its highest and best use, or a cost approach used beside a directly determined land value, never with the land backed out as the residual. A cost segregation study relies on that split twice: the land share is not depreciable, and for a building purchased in a qualified opportunity zone the building’s adjusted basis, as determined under §1012, is the amount that additions during the 30-month period must exceed (50 percent of it for property in a qualified opportunity zone comprised entirely of a rural area), with the land under it not required to be separately improved (Treas. Reg. §1.1400Z2(d)-2(b)(4)(iv)(A) and (E)); the study documents that split and does not lower the threshold, and whether the test is met is a determination for the fund’s tax counsel.
Does the 10-year Opportunity Zone hold cover depreciation recapture?
On a qualifying investment held 10+ years, an investor who sells the fund interest and makes the IRC §1400Z-2(c) election to step basis to fair market value excludes the gain on that interest — including depreciation recapture — so the acceleration becomes permanent rather than a timing benefit; if the fund sells the property instead, the hold alone does not exclude the gain, but for a fund taxed as a partnership or S corporation a separate election under Treas. Reg. §1.1400Z2(c)-1(b)(2)(ii) can exclude it, on that regulation’s own conditions; before year ten recapture is entirely normal. The component schedule the study produces is the ledger that documents it, which is why the records matter at exit and not only in the first filing year.
When is a cost segregation study run on an Opportunity Zone acquisition?
At the front of the deal, because the test runs on a 30-month clock that starts at acquisition. Starting early means the land/building split is supported before improvement spending is planned, and the depreciation schedule is ready the moment the property is placed in service. The improvements made to pass the test are themselves full of 5-, 7-, and 15-year property reclassified by the study and, for qualifying property, eligible for 100% bonus depreciation under §168(k) when the property is acquired after January 19, 2025.
