The Certificate of Occupancy is a legal document that most tenants have never seen — and one of the key records for determining whether a building's current use and occupancy are authorized by the Department of Buildings. Here is what it covers, how to look it up, and what to do when the records do not match what you are being shown.
What a Certificate of Occupancy is
A Certificate of Occupancy (C of O or CO) is issued by the NYC Department of Buildings. It establishes the legal use and permitted occupancy of the building, including permitted residential units and floor use where applicable, as well as the occupancy group.
For buildings that are required to have a Certificate of Occupancy, the building or relevant space generally must have a valid CO or Temporary Certificate of Occupancy (TCO) authorizing its occupancy. Buildings constructed before 1938 may be exempt from the CO requirement unless later alterations changed the building's use, egress, or occupancy — in those cases, other DOB records may establish legal use.
The CO must be amended when a building's use or occupancy changes significantly.
What it contains
A Certificate of Occupancy includes: the address, borough, block, lot, and BIN; the certificate type and date; the building occupancy group; the number and description of permitted dwelling units per floor; construction classification; and any additional conditions or restrictions.
For older buildings, the CO may predate modern record systems and be on file as a paper document. The NYC DOB NOW system at a810-dobnow.nyc.gov contains CO records; for older records, the Buildings Information System (BIS) at a810-bisweb.nyc.gov or a direct DOB inquiry may be needed.
Why it matters for tenants
A building being rented for residential use should have applicable DOB records authorizing that use. If a residential space is not authorized by the building's applicable DOB records, that may indicate an illegal conversion or other unauthorized use. Before drawing conclusions, check whether the building is exempt from the CO requirement and whether other DOB records — such as a Letter of No Objection or prior permit history — establish legal use for that space.
Under NY Real Property Law § 235-BB, owners of buildings with three or fewer rental units are required to disclose to prospective tenants — before the lease is signed — whether a valid CO exists for the unit, if a CO is required by law.
A Temporary Certificate of Occupancy (TCO) is common in new construction. A TCO indicates the building is safe to occupy but has outstanding work or permits to complete before a final CO is granted. TCOs are typically issued for 90-day periods and can be renewed. A building that has been operating on a series of TCO renewals for years may have unresolved outstanding conditions.
How to look up a CO
Go to DOB NOW at a810-dobnow.nyc.gov. Search by address. Under the "Certificates of Occupancy" section, you will find the CO on record for the building — including the date it was issued, the occupancy type, and the number of permitted units.
For buildings with records not yet in DOB NOW, search the Buildings Information System (BIS) at a810-bisweb.nyc.gov, or contact DOB directly.
What mismatches mean
Compare the CO to what you are being shown. Common mismatches:
The number of units on the CO is fewer than the units being rented. This may indicate conversions that were not authorized.
The occupancy group on the CO is commercial or mixed-use, but the unit being offered is purely residential. The permitted use of the space matters.
No CO appears in the records. For pre-1938 buildings this may be normal; for newer buildings it warrants further inquiry.
The CO shows residential use but the specific floor or unit you are renting does not appear as a permitted dwelling unit.
What Weverit shows you
The Weverit building report includes the DOB permit history and, where available, CO status. A building with active permit applications may be in the process of obtaining or amending a CO. A building with no permit history and no CO record on a recently converted space is worth investigating before you sign.
Three things to check before you sign
First, ask for the CO or confirm it exists in DOB NOW. For a building with three or fewer rental units, the landlord is required to disclose CO status — if a CO is required by law — before lease signing.
Second, compare the number of permitted units on the CO to the number of apartments in the building. If there are more apartments than the CO authorizes, some of them may not be properly documented.
Third, if the building has a TCO rather than a final CO, ask what outstanding work remains and when it is expected to be completed. A TCO that has been renewed repeatedly for the same reason is a pattern worth understanding before you move in.
Buildings with DOB construction complaints on record
Ranked by DOB complaints about construction work, from reports computed between May 24, 2026 and September 5, 2026.
- 500 West 33 StreetManhattan B+
- 5400 Fieldston RoadBronx D
- 231 Steuben StreetStaten Island D
- 160 Parkside AvenueBrooklyn D
- 401 East 34 StreetManhattan D
- 1845 Sedgwick AvenueBronx F
- 626 1 AvenueManhattan D
- 2470 West 1 StreetBrooklyn D
- 2935 Ocean ParkwayBrooklyn D
- 2501 Davidson AvenueBronx F
Sources
- NYC Department of Buildings — Certificates of Occupancy: nyc.gov/site/buildings/index.page
- NYC DOB NOW — CO Search: a810-dobnow.nyc.gov
- NY Real Property Law § 235-BB (Certificate of occupancy — required disclosure to tenant)
- NYC Department of Buildings — Tenant Guide: nyc.gov/site/buildings/tenant/tenant-guide.page
- NYC DOB — Buildings Information System (BIS): a810-bisweb.nyc.gov
