California Code, Public Contract Code - PCC § 20155.6

(a) If a county elects to award a project pursuant to this article, retention proceeds withheld by the county from the selected best value contractor shall not exceed 5 percent if a performance and payment bond, issued by an admitted surety insurer, is required in the solicitation of bids.

(b) In a contract between the selected best value contractor and a subcontractor, and in a contract between a subcontractor and any subcontractor thereunder, the percentage of the retention proceeds withheld shall not exceed the percentage specified in the contract between the county and the selected best value contractor.  If the selected best value contractor provides written notice to a subcontractor that, prior to or at the time the bid is requested, a bond may be required and the subcontractor subsequently is unable or refuses to furnish a bond to the selected best value contractor, then the selected best value contractor may withhold retention proceeds in excess of the percentage specified in the contract between the county and the selected best value contractor from any payment made by the selected best value contractor to the subcontractor.