Agencies by estoppel rarely occur because of an independent contractor's actions. Rather, agency by estoppel occurs when: a. An independent contractor presents her or his business card to the principal's customer, client, or patient stating that she or he has known the principal for twenty years. b. The principal makes no effort to inform its customers, clients, or patients that its staff consists of only independent contractors. O c. The principal sets out numerous signs throughout its establishment that indicate that all personnel are independent contractors. All customers, clients, or patients must sign a waiver stating that they understand that all of the principal's personnel are independent contractors. Check My Work Icon Key