Check the CO Before You Sign: Avoid Illegal NYC Apartments
TL;DR - Before you hand over first month's rent or a deposit, check whether the apartment is legal to occupy as advertised. NYC's DOB and HPD tools can show whether the building has a Certificate of Occupancy, a Temporary Certificate of Occupancy, or red flags for an illegal conversion.
NYC renters are trained to move fast: tour, decide, apply, send documents, hope the place is still available. That speed matters, but there is one check you should not skip just because the broker is pushing for a same-day answer.
Make sure the apartment is legal to live in.
That does not mean becoming an architect or reading every DOB filing. It means doing a tight, practical occupancy check before you commit real money. Is the space actually approved for residential use? Is that basement apartment legal? Is the "loft" really a legal dwelling, or is it a commercial space with a couch? Does the unit have the basic safety signals NYC tells renters to look for?
This guide is the fast version: what to look up, what the terms mean, and when to slow down before signing.
The 10-minute occupancy check
When you have the exact address and unit, do this before sending serious money:
- Search the address in DOB's Building Information System or DOB NOW Public Portal.
- Look for the Certificate of Occupancy, Temporary Certificate of Occupancy, or floor/use records.
- Compare the legal use to what you are being offered: residential apartment, number of dwelling units, floor, basement/cellar status, and any obvious mismatch.
- Check DOB and HPD red flags: illegal conversion complaints, vacate orders, active violations, or work that changed occupancy without a clear approval path.
- If the space looks questionable, ask the broker or owner for the relevant CO, TCO, Letter of No Objection, or written explanation before you pay anything beyond an ordinary application fee.
This is not about killing every deal with paperwork anxiety. It is about catching the big mismatches before they become your problem.
What a Certificate of Occupancy actually tells you
A Certificate of Occupancy, usually called a CO, is a DOB document that states the legal use and permitted occupancy of a building. DOB says new buildings need a CO, and existing buildings need a current or amended CO when there is a change in use, egress, or type of occupancy. DOB also says no one may legally occupy a building until DOB has issued a CO or Temporary Certificate of Occupancy.
For renters, the key phrase is "legal use." A CO can tell you whether a building or floor is approved for residential use, how the building is classified, and whether a particular occupancy setup makes sense.
A Temporary Certificate of Occupancy, or TCO, is different. It allows occupancy while final items are being completed. DOB treats it as temporary, so if you are renting in a new development or recently converted building, ask whether the TCO is current and whether the apartment you are renting is covered.
Older buildings can be confusing. DOB says buildings built before 1938 were not required to have a CO unless later changes triggered one. For those buildings, DOB may issue a Letter of No Objection to confirm legal use. So "no CO found" is not automatically a scam. It is a prompt to ask: is this a pre-1938 building, and what document confirms the current legal residential use?
How to look it up
DOB gives renters two main places to start:
- BIS: The Building Information System has property profile pages, older permits, complaints, violations, and occupancy information.
- DOB NOW Public Portal: DOB NOW includes newer applications and certificate of occupancy details for requests submitted on or after March 1, 2021.
Search by address. If you find a CO, open the PDF or certificate details and check the basics:
- Does the building use include residential occupancy?
- Does the floor described match the apartment you toured?
- Does the number of dwelling units roughly match the way the building is being used?
- Is the apartment in a basement, cellar, attic, garage, commercial space, or subdivided room setup?
- If only a TCO appears, is it current rather than expired?
You do not need to decode every line. You are looking for a common-sense match between the city record and the apartment being sold to you.
Basement, cellar, attic, and flex-room red flags
Basement and cellar listings need extra caution. HPD explains that a basement is partly below curb level with at least half its height above curb level, while a cellar has more than half its height below curb level. HPD says basements and cellars can never be lawfully rented or occupied unless they meet minimum requirements for light, air, sanitation, and egress and have DOB approval. HPD also says cellars in one- and two-family homes can never be lawfully rented.
DOB's illegal conversion guidance gives renters practical warning signs. Be careful with apartments advertised as basement or attic spaces, rooms without windows, very small windows, "flex" conversions, utilities included because separate utility setup is not available, odd layouts, no exact address before viewing, no mail delivery, no lease, cash-only payment, padlocked rooms, or limited exits.
Some of those signs can appear in legal apartments too. But several together should slow you down immediately.
Here is the simple rule: if the listing's value depends on a space being used as a bedroom, apartment, or private dwelling, make sure city records support that use.
What to ask before you pay
If the occupancy record is unclear, keep the message short and concrete:
"Before I send move-in funds, can you send the Certificate of Occupancy, current TCO, or Letter of No Objection showing this unit is legal for residential occupancy as shown?"
For a basement, cellar, attic, loft, converted commercial space, or subdivided apartment, add:
"Can you point me to the DOB record showing this specific use is approved?"
A legitimate broker or owner may need a little time to pull documents. That is fine. What you do not want is pressure plus vagueness: "Everybody rents it this way," "the city does not care," "we only do cash," "no lease," or "send the deposit first and we will handle paperwork later."
Do not let urgency scramble the order. Verify first, then commit.
How this fits into a fast apartment hunt
You do not need to run a full records audit on every listing you save. Use a two-tier approach.
For ordinary apartments in clearly residential rental buildings, do the quick check once a listing becomes serious: before applying if something feels off, and definitely before sending move-in funds.
For unusual apartments, do it earlier. That includes basements, cellars, attic spaces, lofts, rooming-house setups, "private floor" shares, commercial-looking buildings, fresh conversions, and apartments where the address or unit number is weirdly hard to confirm.
The fastest renters are not reckless. They have a short due-diligence routine ready before the good listing appears. Keep your application packet ready, set alerts for apartments that match your budget and neighborhoods, and build this CO check into the moment between "I want it" and "I am sending money."
RentReboot can help you find relevant listings and move quickly when they match your criteria. It cannot certify that a space is legal or replace DOB and HPD records. Use alerts for discovery; use city records for the occupancy sanity check.
A practical play-by-play
Say you find a below-market garden-level apartment in a two-family house in Astoria. The photos look good. The listing says "basement apartment," utilities included, private entrance, cash discount available.
Here is the move:
- Ask for the exact address and unit before viewing.
- Search DOB records for the building.
- Look for a CO or other record showing the building can legally contain the rental setup being offered.
- Check whether the space is a basement or cellar and whether HPD's warning signs are present.
- During the tour, look for windows, exits, smoke and carbon monoxide detectors, extension-cord electricity, padlocked rooms, and whether mail delivery is normal.
- If anything does not line up, ask for the CO/TCO/LNO or DOB approval before sending money.
If the answer is pressure instead of documentation, walk. A cheaper apartment is not cheap if a vacate order, safety issue, or illegal-use dispute forces you back into the market.
Quick FAQ
Does every NYC building have a Certificate of Occupancy? No. DOB says buildings built before 1938 were not required to have one unless later changes required a new or amended CO. For older buildings, a Letter of No Objection may confirm legal use.
Is a Temporary Certificate of Occupancy enough? It can allow occupancy while final work is completed, but it is temporary. If a building relies on a TCO, ask whether it is current and whether your apartment is included.
Are all basement apartments illegal? No, but HPD says basements and cellars can only be lawfully rented or occupied if they meet minimum requirements and have DOB approval. HPD says cellars in one- and two-family homes can never be lawfully rented.
What if the broker will not give me the exact address? That is a red flag. DOB specifically warns renters to be cautious when a landlord refuses to disclose the exact address.
Can I report a suspected illegal conversion? Yes. NYC 311 accepts building conversion or occupancy complaints, including illegal apartments created from altered basements, cellars, attics, or illegally subdivided spaces.
Bottom line
You can move fast and still be careful. Before you send meaningful money, make sure the apartment's legal occupancy story makes sense: CO, TCO, LNO, or another clear DOB record for the way the space is being rented.
Find the listing quickly. Verify the building quickly. Then decide with your eyes open.
👉 Set up RentReboot alerts to find NYC apartments that match your search, then run this occupancy check before you sign.
Sources
- NYC Department of Buildings - Certificate of Occupancy
- NYC Department of Buildings - Find Building Data
- NYC Department of Buildings - Looking to Rent
- NYC Department of Buildings - Spot an Illegal Conversion
- NYC Department of Buildings - Illegal Conversion
- NYC HPD - Basements and Cellars
- NYC 311 - Building Conversion or Occupancy Complaint