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    What Is a Certificate of Occupancy?

    A plain-English guide to the NYC Certificate of Occupancy (CO) — what it authorizes, the difference between CO and TCO, when a new one is required, the multi-agency process to obtain one, and what happens if a building operates without a valid CO.

    Certificate of Occupancy: The Definition

    A Certificate of Occupancy (CO) is the legal document issued by the NYC Department of Buildings that authorizes a building to be occupied for a specific use. It confirms that the building complies with the Building Code, Zoning Resolution, and Certificate of Occupancy filed plans — and specifies exactly what use is legally permitted on each floor.

    Every building constructed after 1938 is required to have a CO. Any building constructed before 1938 without one is subject to the Housing Maintenance Code and Multiple Dwelling Law for its allowed use. Once a building has a CO, that use is legally locked in — changing it requires a new CO.

    If you need to obtain, amend, or renew a CO, see our Certificate of Occupancy service.

    When a New Certificate of Occupancy Is Required

    A new (or amended) CO is triggered any time the building's use, occupancy, or configuration changes in a way that departs from the current CO:

    • New construction — Every new building must obtain a CO before it can be legally occupied.
    • Additions or enlargements — Adding square footage typically requires an amended CO showing the new dimensions and use.
    • Change of use or occupancy group — Converting residential to commercial (or vice versa), or from one occupancy group to another, requires a new CO. See our Change of Use guide.
    • Alteration Type 1 (ALT-1) — Alterations that change the building's use, occupancy, or exits require a new CO. See the Building Permits guide.
    • Subdivision of dwelling units — Splitting or combining apartments changes the CO.
    • Rooftop or cellar occupancy changes — Adding a rooftop bar or converting a cellar into occupiable space triggers CO amendment.

    Temporary CO (TCO) vs. Final CO

    Owners often ask about the difference between a Temporary Certificate of Occupancy (TCO) and a final CO. Both authorize occupancy, but they carry very different terms:

    Temporary CO (TCO)

    • Valid for 90 days (renewable)
    • Issued when work is substantially complete but final sign-offs are pending
    • Requires clearance from FDNY, HPD, Sanitation, etc.
    • Must be renewed until a Final CO issues
    • Common for large new-construction projects moving in tenants

    Final CO

    • Permanent — no expiration date
    • Issued only after all sign-offs are complete
    • Represents full legal occupancy authorization
    • Filed with the property record; appears on title searches
    • Required to close on most sales and refinances

    For a longer comparison, see our blog on TCO vs CO and how to obtain a Temporary CO.

    How the CO Process Works

    1

    Filing & Plan Approval

    The project files with DOB (typically ALT-1 or NB), plans are examined for code and zoning compliance, and the permit is issued.

    2

    Construction & Inspections

    As the project builds, DOB conducts progress inspections. Trade inspections (plumbing, electrical, sprinkler) close out along the way.

    3

    Multi-Agency Sign-Offs

    Before a CO can issue, other agencies must sign off — FDNY (fire safety), HPD (residential), DOT (curb cuts, sidewalk), and others depending on the project.

    4

    Final Inspection & CO Issuance

    DOB conducts a final inspection. Once all sign-offs are in and the building is code-compliant, DOB issues the Final CO. If some sign-offs are still pending, a TCO can bridge the gap.

    What Happens Without a Valid CO?

    Operating a building outside its CO — or without any CO — is a serious enforcement issue. Consequences include:

    • Class 1 DOB violations for occupancy without a CO
    • Vacate orders forcing occupants out until compliance is restored
    • Blocked property sales — lenders and title insurers require valid CO for most transactions
    • Voided insurance coverage for the improper use
    • Personal criminal liability for continued illegal occupancy
    • Cascading tenant issues — rent-stabilized tenants may not owe rent when the unit's CO doesn't authorize residential use

    Need to obtain, amend, or renew a CO?

    BVS handles the full CO process — from initial filing through multi-agency sign-off. Learn more about our Certificate of Occupancy service or contact BVS for a free consultation.