Certificate of Occupancy: How to Read One

A certificate of occupancy (CO) is the Department of Buildings document that states a building’s legal use and type of occupancy, often floor by floor and including how many apartments are allowed. If the apartment you are looking at is on a floor or in a space the CO does not allow for living, or the building has more apartments than the CO lists, the unit may not be legal.

Below: what a CO shows, what a temporary CO means, what to do when an older building has no CO at all, and a decision tree that turns the CO into a practical verdict.

What a certificate of occupancy tells you

DOB says a CO “states a legal use and/or type of permitted occupancy of a building,” and that no one may legally occupy a building until DOB has issued a CO or a temporary CO. New buildings must have one. Existing buildings need a new or amended CO when there is a change in use, egress (exits) or type of occupancy, such as turning a two-family house into a three-family house.

When you open a CO, look for these parts:

How to find a building’s CO

1. 1

   COs issued before March 1, 2021: BIS

   Search the address in DOB’s Buildings Information System (BIS). On the Property Profile Overview, select “View Certificates of Occupancy.” Issued COs are listed as PDF files you can open and print.
2. 2

   COs issued on or after March 1, 2021: DOB NOW

   Use the address search in DOB NOW. At the top of the Property Profile page, select Certificate of Occupancy. You can print it from there.
3. 3

   Read the latest one, then the earlier ones

   A building can have several COs over time. The most recent one normally reflects the current approved use; earlier ones show how the building changed. If you are unsure which one governs, ask an architect or attorney.
4. 4

   Cross-check the unit count

   Compare the CO’s dwelling-unit total with the residential units shown on the building’s Roofy building page, the number of mailboxes and doorbells, and the listing.

Temporary certificates of occupancy

A temporary CO (TCO) is issued when DOB finds a property safe to occupy but some issues remain before a final CO. DOB says TCOs typically expire 90 days after issuance and can be renewed if the outstanding items are not resolved. DOB also says that if the space is not occupied for more than 30 days, a new TCO is needed to re-occupy it. In DOB’s CO dataset for July 2012 to March 2021, new-building records include 32,154 temporary COs and 21,341 final COs, so living in a new building on a TCO is common.

For a renter, a current TCO is a legal basis to occupy. For a buyer of a new-development condo, a building still on a TCO long after move-ins is a due-diligence item: ask what is outstanding. See buying a new development condo.

Buildings with no CO

DOB says buildings built before 1938 are not required to have a CO unless later alterations changed their use, egress or occupancy. Many brownstones and pre-war walk-ups fall in this group. For these buildings, DOB may issue a Letter of No Objectionto confirm the legal use; you request one from the DOB borough office.

“No CO found” in a post-1938 building, or in an older building that was obviously converted (a former factory, a house cut into many apartments), is a different story. Look for the A1 or Alteration CO job that should have produced a new CO; see how to read DOB permits and job filings.

Minor alterations that do not change use, egress or occupancy end with a Letter of Completion instead of a new CO, so a renovated apartment does not need its own CO.

Basements and cellars

The CO is the quickest way to spot an illegal basement or cellar apartment. HPD defines the two differently:

• Basement: a story partly below curb level, with at least half its height above curb level.
• Cellar: an enclosed space with more than half its height below curb level.

HPD says cellars in one- and two-family homes can never be lawfully rented or used for sleeping. A basement can be legal only if it meets minimums for ceiling height (at least 7 feet), light, air, windows and exits, and renting a basement in a two-family home may change the building’s status and require a new CO. Read the full rules in basement and cellar apartments in NYC.

Is this apartment a legal unit? Decision tree

Answer a few questions about what you found. The result is a starting point, not a legal opinion.

Limits

• DOB’s open datasets index COs (2012 to March 2021 in one dataset, March 2021 onward in another); older COs exist only as scanned images in BIS.
• Old scanned COs can be hard to read, and the address on an old CO may differ from today’s. Search by block and lot if needed.
• A CO says what was approved, not what is there today. A building can match its CO on paper and still have an illegal unit; the walk-through matters. Use our apartment viewing checklist.