Legally binding agency relationship that may arise where, in fact, no formal agency agreement is in effect. A principal may give an appearance of agency relationship by, for example, furnishing his or her firm's call cards or other stationery to the agent. In such cases, the existence of an agency may be presumed, and the principal may be bound by the acts of the agent performed on the principal's behalf. Also called presumption of agency. See also partnership by estoppel.