Certificate of occupancy

The DOB document stating what a building is legally allowed to be used for and how many people or units it may hold.

The certificate of occupancy, or C of O, is the building's legal identity: use, occupancy limits, floor by floor. A building used contrary to its certificate (an illegally converted dwelling, an extra unit carved out of a cellar) is violating even if every wall is sound. Older buildings may lawfully have no C of O at all if their use has not changed since before 1938.

Getting a new or amended certificate requires the building's DOB record to be in order, which is one of the ways open violations quietly cost owners: the record blocks the paper.