Affiliates are business concerns, organizations, or individuals that control each other or that are controlled by a third party. Control may consist of shared management or ownership; common use of facilities, equipment, and employees; or family interest. The employees or receipts of all affiliates are included when stating the firm's size. The power to control is the key factor in affiliation with another business concern, whether exercised or not.

Indicators of affiliation include common ownership, common management and identity of interest, among others. Power to control exists when a party or parties have 50 percent or more ownership. It may also exist with considerably less than 50 percent ownership by contractual arrangement or when one or more parties own a large share compared to other parties. The affiliated business concerns may conduct business in unrelated areas.