Legal use of a building

Certificate of Occupancy in NYC — CO, TCO, and When It Matters

What a NYC Certificate of Occupancy proves, how to find one, what pre-1938 buildings and TCOs mean, and how CO problems affect renovations and closings.

Last reviewed: 2026-07-13

A Certificate of Occupancy (CO) is the Department of Buildings document that states what a building may legally be used for and how many people or families may occupy it: two-family dwelling, six-story apartment building with ground-floor retail, and so on. When lawyers, lenders, architects, or buyers ask “what is this building, legally?” — the CO is the answer they mean.

It sounds bureaucratic until it isn’t: a mismatch between the CO and how a building is actually used is one of the most expensive surprises in NYC real estate, and it tends to surface at the worst moment — mid-closing, mid-refinance, or mid-inspection.

How to find a CO (free, five minutes)

1. Search the address in DOB’s Building Information Search (BIS) or the DOB NOW public portal.
2. Open the “Certificate of Occupancy” section of the property profile. Scanned COs — often decades old — are viewable as PDFs.
3. Read the use and occupancy lines for each floor. Compare them with reality: unit count, commercial uses, basement occupancy.
4. Note the CO number and issue date for your records.

While you have the property profile open, it is worth running the NYC violation lookup too — CO problems and open violations often travel together.

The three situations you will encounter

1. A final CO exists

The clean case. Verify that actual use matches. A legal two-family being rented as three units is not a paperwork nuance — it is an illegal conversion with insurance, eviction-law, and life-safety consequences, and it can generate DOB violations and vacate orders.

2. The building is pre-1938 and has no CO

Buildings constructed before 1938 were not required to obtain a CO, and many rowhouses and small apartment buildings lawfully have none. If the use has never changed, that is normal. Where documentation of legal use is needed — closings, some permits and licenses — the DOB borough office can issue a Letter of No Objection (LNO) confirming it does not object to the stated use. Records that support an LNO application (old I-cards, tax records, alteration history) are worth gathering before you need them.

3. A TCO — Temporary Certificate of Occupancy

A TCO allows a building (or part of it) to be occupied while some requirements for the final CO remain open. TCOs are common in new construction and major alterations, and they expire: they must be renewed until the final CO is issued. A building that has been “temporarily” occupied for years on a chain of TCO renewals is a known NYC phenomenon — and a red flag in due diligence, because anything that interrupts renewal (an open violation, an expired insurance certificate, a lapsed permit) can leave the building formally without any occupancy authorization.

When a renovation changes the CO — and when it doesn’t

The dividing line is use, egress, or occupancy: change any of the three and the project generally must be filed in a way that ends with a new or amended CO. This is a major scoping decision at the start of a renovation, not an afterthought — it changes the filing type, the professional team, the timeline, and the budget. If the answer is unclear, resolving it is a proper question for a registered design professional, and shepherding the paperwork is where a permit expediter earns their fee.

Skipping the paperwork does not work in the long run: unpermitted work that should have amended the CO surfaces at resale, generates violations, and can trigger a Stop Work Order when discovered mid-project.

CO problems at sale and refinance

• Buyers and lenders check. Title companies and attorneys routinely pull the CO; mismatches become escrow holdbacks, price concessions, or dead deals.
• Expired TCOs are financing problems. Many lenders will not close on an expired TCO; sellers end up racing to renew or to clear the items blocking the final CO.
• Fixes take time. Curing a CO problem may require legalization filings, inspections, and clearing DOB and HPD records first — see HPD violations explained for the housing-side records that can block sign-offs. Start months before a planned closing, not weeks.

Bottom line

The CO defines what your building legally is. Read it before you buy, before you renovate, and before you list — and if what you find doesn’t match reality, treat resolving it as a project with professionals, deadlines, and a budget, because that is what it will become either way.

Official sources

• DOB Certificate of Occupancy overview
• DOB Building Information Search (BIS)
• DOB NOW public portal