Picture an employee handed a written job description. What is written down, what the job obviously requires, and what the boss lets customers believe are three different sources of power. An agent's authority works the same way.
Express authority: stated in the agency contract.
Implied authority: what is needed to carry out the express authority.
Apparent authority: what the principal, by its own conduct, leads a third person to believe the agent has. Civil Code §2317 calls it ostensible authority: authority the principal, intentionally or by want of ordinary care, causes or allows a third person to believe the agent possesses.
Apparent authority is what binds an insurer after it forgets to clean up. If an insurer ends an agent's appointment but leaves its sign on his office and keeps him listed on its website, a client who pays him a renewal premium can rely on apparent authority. Express and implied authority ended with the appointment; apparent authority came from the insurer's own conduct.
Field underwriting: the producer is the insurer's first screen. She gathers accurate information, follows the insurer's underwriting guidelines and requirements, and passes on what she observes, such as a wood stove or a home business the application does not mention. A producer with no binding authority does not accept or reject the risk; that decision belongs to the underwriter. Leaving facts out harms the insurer and can harm the applicant's coverage.