Prime contractor
In short
Carries two senses: the contractor holding the owner's contract, and the party liable for the tax. They are not always the same party.
In full
A.R.S. § 42-5075(S)(10) defines a prime contractor as a contractor who supervises, performs or coordinates the modification of any building, highway, road, railroad, excavation, manufactured building or other structure, project, development or improvement — including the contracting, if any, with subcontractors or specialty contractors — and who is responsible for the completion of the contract.
Responsibility for completion is the operative half. Supervising or coordinating without carrying that responsibility does not make a party the prime.
The same paragraph then rules out the case contractors most often assume is covered. A person who owns real property, engages one or more contractors to modify it, and does not itself modify it is **not** a prime contractor — regardless of a contract for sale or a subsequent sale of the property. Two exceptions are named: subsection (E), where a person gives a certificate claiming to be the prime and is deemed to be one, and subsection (R), which reaches an owner who sells and remains responsible for modifications made after title transfers.
Where an owner improves property for sale and neither exception applies, the classification to check is a city one — Speculative Builder or Owner-Builder under the Model City Tax Code, not state prime contracting.
The term also carries a second sense in ordinary trade use: the contractor holding the contract with the property owner and running the project. That usually describes the same party the statute does, but not always, which is why a certificate rather than an assumption establishes who is liable.
The role is decided per contract. A contractor can be the prime on one contract and a subcontractor on the next, and each contract is evaluated independently under (P)(2).
A.R.S. § 42-5075(S)(10), (E), (R), (P)(2)