I purchased a building in a QOZ that is currently vacant. Is the building “original use” property

No, the building is not considered "original use" property.

The term "original use" of tangible property in a Qualified Opportunity Zone (QOZ) generally refers to the first time the property is placed in service in a manner that would start depreciation or amortization if the property were being used in a trade or business. For a building to be considered "original use" property, it must not have been previously placed in service in the QOZ.

However, there is a specific provision for vacant property. According to the regulations, vacant property, including a building, can be considered "original use" property if it meets one of the following conditions:

1. The property was vacant for an uninterrupted period of three years beginning after the date the IRS designated the census tract as a QOZ.
2. The property began to be vacant at least one year prior to the date when the IRS designated the census tract as a QOZ and remained vacant through the date of the purchase.

If the building you purchased does not meet either of these conditions, it cannot be considered "original use" property. Instead, to qualify as Qualified Opportunity Zone Business Property (QOZBP), the building would need to be substantially improved. This means that during any 30-month period beginning after the date of acquisition, the additions to the basis of the building must exceed the adjusted basis of the building at the beginning of the 30-month period.

Sources:
§ 1.1400Z2(d)-1. Qualified opportunity funds and qualified opportunity zone businesses.
Rev. Rul. 2018-29
Instructions for Form 8996 (12/2023)
§ 1.1400Z2(d)-2. Qualified opportunity zone business property.
Qualified Opportunity Zones: Final Regulations Provide Clarity