Ind. Code § 5-16-5.5-2
To the extent that this chapter is applicable, all contracts between a contractor and a state agency concerning any public building, work, or improvement entered into after May 1, 1972, and which contracts are in excess of two hundred thousand dollars ($200,000) are to be governed by the provisions of this chapter, as are the rights and duties among the parties to the contract and any subcontractors who do any work under the contract. A state agency may elect to have a contract that is for not more than two hundred thousand dollars ($200,000) be governed by this chapter. All contracts governed by the provisions of this chapter shall include provisions for the retainage of portions of payments by a state agency to contractors, by contractors to subcontractors, and for the payment of subcontractors.
IC 5-16-5.5-2