What Is a BBL?

A BBL (Borough-Block-Lot) is the unique identifier assigned by New York City to every tax lot. It appears on deeds, mortgage documents, permits, tax bills, and virtually every official city record tied to a piece of real property. If you research NYC real estate — as an attorney, investor, architect, journalist, or tenant — understanding BBLs is foundational.

Structure of a BBL

A BBL is a 10-digit number broken into three parts:

In hyphenated form, leading zeros in the block and lot are often omitted: 3-01607-0023 or 3-1607-23 both refer to the same lot. The canonical 10-digit form is 3016070023.

How Are BBLs Assigned?

The block corresponds to the city block bounded by streets — it's the same block you'd point to on a map. The lot is a subdivision of that block. Lots are numbered sequentially, typically starting from the corner of the block. Condominium units have individual lot numbers (often in the 7000–8999 range). Air rights lots are in the 1000–1999 range.

The NYC Department of Finance assigns and maintains BBLs. Changes happen when lots are subdivided, merged, or split off as condominiums. NYC Planning's PLUTO dataset is the authoritative source for all active tax lots and their attributes.

Where to Find a BBL

• Tax bills — listed as "Borough-Block-Lot" on every NYC property tax bill
• Deeds and mortgage documents — required field on all recorded instruments in ACRIS
• DOB permits and filings — the BIS system cross-references BBL with BIN
• NYC Finance property search — acris.nyc.gov
• Lotlyze — type any address and the BBL is resolved instantly from the geocoder

BBL vs. BIN

A BIN (Building Identification Number) identifies a specific building, not a lot. A single BBL can have multiple BINs (a lot with multiple structures), and a condo building has one BIN shared across many BBLs. For most lookups, you need both: BBL for ownership/deed research, BIN for permits and violations. See: What is a BIN?

BBL in Open Data APIs

NYC's Socrata-based Open Data APIs use BBL as a join key across datasets. The canonical format in most endpoints is the 10-digit string (no hyphens):

# ACRIS: look up deed records by BBL
GET https://data.cityofnewyork.us/resource/8h5j-fqxa.json?
    borough=3&block=01607&lot=0023

# PAD (Property Address Directory): resolve BBL to BIN
GET https://data.cityofnewyork.us/resource/5zhs-2jue.json?
    base_bbl=3016070023