An interpretive rule is a document an agency issues to explain its own regulations or to explain the meaning of a statute that it administers. If a document is truly an "interpretive rule," the APA allows the agency that is issuing it do so without following notice-and-comment procedures. (See Rulemaking Exceptions.)

Sometimes an agency, in the guise of "interpreting" a law or regulation, may add new content or requirements to them. In such an instance, a challenger may succeed in persuading a reviewing court to invalidate the interpretation for failure to follow notice-and-comment procedures. As with guidance, each document must be examined individually to determine whether it is what it purports to be. (See Guidance.)

Agencies sometimes issue interpretations or rulings that are applicable to (and may only be relied on by) the individuals who request them. An Internal Revenue Service "Letter Ruling" is an example.