Classification societies are organizations that survey and classify ships, both during their construction and operation. They are the principal means by which standards of construction and maintenance are enforced, and ship certificates can be issued by Flag States.
In order to be registered a ship must be certified to be of a particular type and size and to be maintained to certain minimum standards. Classification societies are licensed by states (national governments) to undertake this work on their behalf. Most states do not insist that ships be “classed.” However, without a “class” there would be considerable difficulties in operating a ship, as “class” is generally a requirement of most insurance companies and shippers using the vessel.