If the value of the contract is over $750,000 and there are subcontracting possibilities then a subcontracting plan is required. See FAR 19.702
"19.702 Statutory requirements.
Any contractor receiving a contract with a value greater than the simplified acquisition threshold must agree in the contract that small business, veteran-owned small business, service-disabled veteran-owned small business, HUBZone small business, small disadvantaged business, and women-owned small business concerns will have the maximum practicable opportunity to participate in contract performance consistent with its efficient performance. It is further the policy of the United States that its prime contractors establish procedures to ensure the timely payment of amounts due pursuant to the terms of their subcontracts with small business, veteran-owned small business, service-disabled veteran-owned small business, HUBZone small business, small disadvantaged business, and women-owned small business concerns.
(1) Except as stated in paragraph (b) of this section, section 8(d) of the Small Business Act (15 U.S.C. 637( d)) imposes the following requirements regarding subcontracting with small businesses and small business subcontracting plans:
(i) In negotiated acquisitions, each solicitation of offers to perform a contract that is expected to exceed $750,000 ($1.5 million for construction) and that has subcontracting possibilities, shall require the apparently successful offeror to submable subcontracting plan....."