What is the implied authority possessed by an agent sometimes referred to as?

The implied authority of an agent is actually referred to as actual authority, which includes both express authority and implied authority. Actual authority encompasses the power granted to an agent through direct communication from the principal (express authority) as well as that which is necessary to carry out express authority (implied authority). While implied authority refers to the abilities and actions that can reasonably be inferred based on the position or responsibilities delegated to an agent, it is not termed incremental authority.

Express authority is specifically the clear, articulated power given to an agent by the principal, while "authority to act" is a more general term and does not specifically define the nature of implied authority. Thus, the label of 'implied authority' aligns directly with the concept of actual authority, distinguishing it from the other terms provided in the question.