Indiana Code Title 6. Taxation § 6-2.5-4-9

Sec. 9. (a) A person is a retail merchant making a retail transaction when the person sells tangible personal property which:

(b) A contractor is a retail merchant making a retail transaction when the contractor:

under a time and material contract.  As such a retail merchant, a contractor described in this subsection shall collect, as an agent of the state, the state gross retail tax on the resale of the construction material and remit the state gross retail tax as provided in this article.

(c) Notwithstanding subsections (a) and (b), a transaction described in subsection (a) or (b) is not a retail transaction, if the ultimate purchaser or recipient of the property to be added to a structure or facility would be exempt from the state gross retail and use taxes if that purchaser or recipient had directly purchased the property from the supplier for addition to the structure or facility.