FAR 19.501 says the purpose of small business set-asides is to award certain acquisitions exclusively to small business concerns. A set-aside limits an acquisition exclusively to participation by small business concerns identified in FAR 19.000(a)(3), which include small business, 8(a) participants, HUBZone small business concerns, service-disabled veteran-owned small business concerns eligible under the SDVOSB Program, and economically disadvantaged women-owned and women-owned small business concerns eligible under the WOSB Program. A set-aside may be total or partial. All solicitations involving set-asides or reserves must specify the NAICS code or codes and corresponding size standard or standards.
FAR 19.502-2(a) says that each acquisition of supplies or services with an anticipated dollar value above the micro-purchase threshold but not over the simplified acquisition threshold shall be set aside for small business unless the contracting officer determines there is not a reasonable expectation of obtaining offers from two or more responsible small business concerns that are competitive in terms of fair market prices, quality, and delivery. If only one acceptable offer from a responsible small business arrives, the contracting officer should award to that firm. If none arrive, the set-aside is withdrawn and, if the requirement is still valid, resolicited unrestricted. Before using that paragraph, the contracting officer must refer to FAR 19.203(b).
FAR 19.502-2(b) says that for acquisitions over the simplified acquisition threshold, the contracting officer shall set the acquisition aside for small business when there is a reasonable expectation of offers from at least two responsible small business concerns and award at fair market prices. Before using that paragraph, the contracting officer must refer to FAR 19.203(c). Except as authorized by law, FAR 19.501(f) says a contract may not be awarded as a result of a small business set-aside if the cost to the awarding agency exceeds the fair market price.