Iowa Code § 216B.8: Contract bids.

A bidder awarded a contract with the department shall disclose the names of all subcontractors, who will work on the project being bid, within forty-eight hours after the award of the contract. If a subcontractor named by a bidder awarded a contract is replaced, or if the cost of work to be done by a subcontractor is reduced, the bidder shall disclose the name of the new subcontractor or the amount of the reduced cost.