Certificate of occupancy (CO)
The local construction official's approval to use a new building, an addition, or a building whose use is changing. Under New Jersey's Uniform Construction Code, these cannot be used until the CO is issued.
New Jersey example
Made-up example: a builder finishes a new house in Jackson, and no one can move in until the construction official issues a CO. Buying an older house is different. The state code lets an existing building's legal use continue, except where a property or fire safety maintenance code or housing standard says otherwise, so resale checks come from those codes, not a new CO.
Official source
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.