IACS

The International Association of Classification Societies is the body that develops the unified requirements and common rules its member societies apply, and that holds consultative status at the IMO. Its twelve members class the great majority of the world fleet by tonnage, and IACS Unified Requirements (such as UR S on hull structure) become de facto mandatory because flag states and the IMO adopt them. Membership turns on quality-system audits; a society can be admitted, suspended, or expelled, which directly affects the standing of the ships it classes.