What Is a Certificate of Occupancy?

A Certificate of Occupancy (C of O) is an official document issued by the NYC Department of Buildings (DOB) certifying that a building complies with the Building Code and Zoning Resolution and is approved for a specific use and occupancy. It is one of the most critical documents in NYC real estate — a building cannot legally be occupied without a valid C of O or equivalent occupancy authorization.

What the C of O Contains

A Certificate of Occupancy is a detailed document that specifies every aspect of a building's approved use:

• Permitted use for each floor — residential, commercial, manufacturing, community facility, or mixed-use designations for every story, cellar, and sub-cellar
• Occupancy group and classification — the NYC Building Code assigns occupancy groups (e.g., J-2 for multi-family residential, E for commercial, F-1 for manufacturing) that determine which fire and safety codes apply
• Maximum number of occupants — calculated based on floor area and use type, this limits how many people can legally occupy each space
• Construction classification — fireproof (Class 1), semi-fireproof (Class 2), non-fireproof (Class 3-6), or wood-frame construction, which affects insurance rates and permitted building height
• Building dimensions — height, number of stories, lot coverage, and floor area ratio (FAR)
• Fire protection systems — type of sprinkler system (wet, dry, or none), fire alarm system, standpipe classification, and emergency lighting
• Special conditions — any restrictions, variances, or special permits from the Board of Standards and Appeals (BSA)

When a C of O Is Required

Under NYC Building Code Section 28-118.3, a new Certificate of Occupancy is required for:

• New building construction — every new building must receive a C of O before it can be occupied
• Major alterations (Alteration Type 1) — work that changes the use, egress, or occupancy of a building, including converting commercial space to residential or adding stories
• Change of use or occupancy — converting from one occupancy group to another (e.g., manufacturing to office, retail to restaurant) even if no physical construction occurs
• Changes to egress or fire safety — adding or removing stairways, changing exit configurations, or modifying fire suppression systems

Minor alterations (Alteration Type 2 and 3) typically do not require a new C of O, as they do not change the building's fundamental use or safety systems. Examples include kitchen renovations, bathroom remodels, and interior partition changes within the same occupancy group.

How to Look Up a Certificate of Occupancy

There are several ways to look up a building's Certificate of Occupancy in NYC:

• DOB BIS (Buildings Information System) — search by address or BIN at bis.nyc.gov. Navigate to the property profile and click the "Certificate of Occupancy" tab to view all issued certificates. BIS has historical records going back decades.
• DOB NOW — the newer DOB portal at a]nycbuild.nyc.gov shows C of O records for recent filings (generally post-2016). Search by address, BIN, or job number.
• RegWatch — enter any NYC address to instantly see the current C of O status, occupancy classification, and any discrepancies between the recorded C of O and actual use. RegWatch cross-references C of O data with violation records to flag potential illegal occupancy issues.

When reviewing a C of O, pay close attention to the date issued, the permitted use for each floor, and whether the document is a final C of O or a Temporary Certificate of Occupancy (TCO).

Temporary Certificate of Occupancy (TCO)

A TCO is issued when a building is substantially complete and safe for occupancy, but certain non-critical items remain unfinished. TCOs are common in new construction and major renovation projects where the building is habitable but items like landscaping, common area finishes, or facade work are still in progress.

Key facts about TCOs:

• Validity — TCOs are valid for 90 days from issuance. They can be renewed multiple times, but each renewal requires a DOB inspection and fee.
• Renewal cost — DOB charges a renewal fee for each 90-day extension. For large developments with multiple TCOs, these fees can total tens of thousands of dollars annually.
• Expiration consequences — if a TCO expires without renewal, the building technically loses its authorization to be occupied. This can trigger DOB violations and create complications for tenants, lenders, and insurers.
• Final C of O requirement — a TCO is not a permanent solution. The building owner must eventually complete all outstanding work items and obtain a final Certificate of Occupancy. Some NYC buildings have operated under continuously renewed TCOs for years or even decades.

Buyers should be cautious about purchasing units in buildings operating under a TCO. Check how long the TCO has been in place, what outstanding items remain, and whether the developer or condo board has a timeline for obtaining the final C of O.

C of O vs. TCO vs. Letter of No Objection (LNO)

NYC has three types of occupancy authorization, each with different implications:

• Certificate of Occupancy (C of O) — the gold standard. A permanent document confirming full compliance with Building Code and Zoning Resolution. Required for all new construction and major alterations post-1938. Does not expire.
• Temporary Certificate of Occupancy (TCO) — a time-limited authorization (90 days) for buildings that are safe but not fully complete. Must be renewed until a final C of O is obtained. Common in new developments.
• Letter of No Objection (LNO) — issued by DOB stating they have no objection to the current use of a building that predates the C of O requirement (pre-1938) or has no C of O on file. An LNO is not the same as a C of O — it does not certify compliance, only acknowledges the existing use. Obtaining an LNO requires providing evidence of the building's use history.

For real estate transactions, a C of O is strongly preferred. An LNO may be acceptable for pre-1938 buildings, but lenders and title companies may require additional documentation. A TCO is acceptable for new construction but buyers should understand the risks of purchasing in a building without a final C of O.

Common C of O Problems in NYC Real Estate

Certificate of Occupancy issues are among the most common problems encountered in NYC real estate transactions:

• Illegal conversions — converting a basement or cellar to a living space without permits, adding a kitchen to create an additional dwelling unit, or converting commercial space to residential use without a C of O amendment. These are especially common in Brooklyn and Queens multi-family properties. Illegal conversions can result in vacate orders and DOB violations.
• Mismatched use groups — the building is being used for a purpose not authorized by the C of O. For example, a building with a C of O for residential use (J-2) being used as a medical office (B) or daycare center (E). This creates liability for the owner and can void insurance coverage.
• Expired or never-renewed TCOs — new developments where the sponsor never obtained a final C of O, leaving the building in a legally questionable occupancy status. This is particularly common in condo conversions from the 2000s-2010s.
• Pre-1938 buildings without documentation — many older buildings have no C of O on file and never obtained an LNO. While this was historically tolerated, modern lenders and insurers increasingly require some form of occupancy documentation, creating complications for sales and refinancing.
• Floor count discrepancies — the C of O may show a different number of stories or dwelling units than what physically exists, often due to unauthorized additions or subdivisions over the decades.

C of O Requirements by Property Type

Different property types have specific C of O considerations:

• 1-4 family homes — require a C of O specifying the number of dwelling units and occupancy group (typically J-3). Adding an accessory dwelling unit (ADU) under the City of Yes program requires a C of O amendment.
• Multi-family (5+ units) — classified as J-2 occupancy. The C of O specifies the number of dwelling units per floor. Any change in unit count (combining or splitting apartments) requires a DOB filing and potentially a new C of O.
• Commercial buildings — classified by specific use (B for office, E for educational, M for mercantile). Converting between commercial uses often requires a new C of O even if no construction work is done.
• Mixed-use buildings — the C of O must specify the permitted use for each floor. Mixed-use buildings are common in NYC (ground floor retail with residential above) and the C of O must accurately reflect each use.
• Condos and co-ops — the building has a master C of O covering all units. Individual unit owners typically do not need their own C of O unless they are altering the use of their specific unit. The condo board or co-op corporation is responsible for maintaining the building's C of O.

Buildings Without a C of O

Many NYC buildings predate the C of O requirement, which was established in 1938. These buildings may have a Letter of No Objection (LNO) instead, which states DOB has no objection to the current use. Buildings without any occupancy documentation can face significant complications during sales, refinancing, and insurance underwriting. Lenders may refuse to issue mortgages, title companies may raise exceptions, and insurers may decline coverage or charge higher premiums. If you own or are purchasing a building without a C of O, consult a licensed architect or professional expeditor about obtaining one.

Impact on Transactions

Lenders, title companies, and insurers routinely review the C of O during real estate transactions. A mismatch between the C of O and the building's actual use is one of the most common reasons for closing delays in NYC. Specific impacts include:

• Mortgage approval — most lenders require a valid C of O (or at minimum an LNO) as a condition of financing. Without it, buyers may be limited to cash purchases or hard money loans.
• Title insurance — title companies may issue exceptions for C of O discrepancies, meaning the buyer is not covered for losses related to occupancy issues.
• Insurance coverage — property insurance policies may contain exclusions for buildings occupied in violation of their C of O. A fire in an illegally converted basement could result in a denied claim.
• Resale value — buildings with C of O problems sell at a discount because buyers factor in the cost and uncertainty of remediation.

Buyers should always verify that the intended use matches the C of O before purchasing, and sellers should address any discrepancies before listing to avoid deal-killing surprises at the closing table.