Certificate of Occupancy

A certificate of occupancy (often abbreviated CO or C of O) is a document issued by the local building department confirming that a building — or a newly created unit within it — complies with applicable codes and is safe and legal to occupy. It is typically the final step in the construction process, granted after the work has passed its final inspection.

The certificate matters because it formally closes out a project. For a new structure, an ADU, or a change of use, occupancy generally cannot legally begin until the certificate is issued. It confirms that the completed work matches the approved plans, that required inspections passed, and that the space meets life-safety standards for its intended use. Some jurisdictions issue a temporary certificate to allow occupancy while minor punch-list items are finished, then a final one once everything is complete and signed off.

The certificate sits at the end of the permit lifecycle that begins with a building permit. After plans are reviewed, the permit issued, and inspections passed at each construction stage, the certificate of occupancy is the document that lets people move in, a landlord rent the space, or a sale close cleanly. Lenders, insurers, and buyers often ask for it as proof the work was permitted and finalized.

The exact name, when it is required, and whether a separate document is issued for an ADU versus the main dwelling vary by jurisdiction and project type. This is general information; confirm the occupancy requirements for your specific project with the local building department.