Census tracts and Opportunity Zones

A census tract is a small, relatively permanent statistical subdivision of a county that the U.S. Census Bureau uses to report data. Tracts typically contain about 1,200 to 8,000 people, with an optimum size around 4,000.³ They nest inside counties, often follow visible features such as roads and rivers, and are split or merged at each decennial census as population changes.³

Because tracts are defined by population, their land area varies enormously. An urban tract can be a few city blocks. A rural tract can cover hundreds of square miles. That difference matters for Opportunity Zones, because the whole tract carries the designation.

The statute requires it. IRC §1400Z-1 defines a qualified opportunity zone as a population census tract that is a low-income community and that has been nominated by the state's chief executive and certified by Treasury.¹ Using tracts lets Treasury apply one uniform, published dataset, the American Community Survey (ACS), to every state.

The ACS is the Census Bureau's ongoing survey of income, poverty and housing. Its five-year estimates are the only ACS product published for every tract, which is why eligibility is measured on a five-year window. For the zones taking effect January 1, 2027, eligibility uses the 2020 to 2024 ACS five-year estimates, released January 29, 2026.⁹

A tract qualifies if it is a low-income community under one of two prongs: an income prong or a poverty prong.^1,4

• Income prong: the tract's median family income (MFI) is no more than 70% of the applicable area median. For a tract outside a metropolitan area, that is the statewide MFI. For a metro tract, it is the greater of the statewide or metro-area MFI.^4,6
• Poverty prong: the tract's poverty rate is at least 20% and its MFI is no more than 125% of the applicable area median.^4,6

Two other rules shape the list. A tract that does not qualify on its own data cannot be designated just because it borders a low-income tract; the rules have no contiguous-tract option.⁴ And a governor may nominate a tract missing from Treasury's list only by supplying tract-level data showing it meets the definition, under Rev. Proc. 2026-14 §5.04.⁶ For a longer treatment of the tests, see which census tracts qualify as Opportunity Zones.

Treasury's list in Rev. Proc. 2026-14 contains 25,332 eligible low-income community tracts, of which 8,334 are wholly rural.⁵

Each state may designate no more than the greater of 25% of its eligible tracts or 25 tracts.¹³ Zones on the current map do not count against that cap for the period starting January 1, 2027. Puerto Rico is subject to the same cap as the states. Governors began nominating on July 1, 2026, with 90 days to file, subject to a single 30-day extension.¹²

How governors pick from the eligible pool is covered in how governors choose Opportunity Zones.

A tract is identified by an 11-digit GEOID, and that number is only meaningful with its vintage, meaning the census whose boundaries it uses. The Census Bureau redraws tracts each decade, splitting fast-growing tracts and merging shrinking ones.³ A tract number from one vintage may cover different ground in another.

The safest workflow is to keep the tract GEOID, its vintage and the source list together in your records. See how to check if a property is in an Opportunity Zone for a step-by-step lookup, and Opportunity Zone maps and data tools for the main tools.^8,2

Proposed regulations published September 11, 2026 (REG-116506-25) would require Qualified Opportunity Funds to report at the census tract level on an expanded Form 8996, including information about each Qualified Opportunity Zone Business they hold.¹⁰ The rules are proposed, not final, but the direction is clear: the tract is becoming the unit of compliance as well as designation.

IRC §6726 adds a penalty of $500 per day for a failure to file a complete and correct return, capped at $10,000 per return, or $50,000 for a fund with gross assets over $10 million.¹⁰ Getting the tract number right is part of getting the return right. See Opportunity Zone reporting requirements.

Large data center campuses are usually in rural or exurban tracts, which are big in area, so a single tract can hold a full campus with its substation. That is helpful. The risks are a parcel that crosses a tract line and a tract whose status changes between the current map and the new one.

• Overlay the full campus boundary, including future phases and any on-site generation or substation land, on tract shapefiles before you sign a purchase contract.
• Confirm the tract is on the certified list for the designation period in which the fund will invest and buy, not just on a nomination list.
• Check whether the tract is wholly rural. That affects the 50% improvement threshold for an existing building and the 30% step-up for a Qualified Rural Opportunity Fund.

The Economic Innovation Group notes there is no enacted rural quota for designations, so whether rural tracts near transmission become zones depends on each governor's choices.¹¹ For siting more broadly, see data center site selection inside Opportunity Zones.