Reference
Every parcel of New York City land that is taxed, regulated, or otherwise tracked by a city agency carries a BBL. The format is 10 digits, no separators in databases. Some web interfaces display the BBL in a hyphenated form (1-01234-0089), but the canonical machine-readable representation is the unbroken 10-digit string (1012340089).
How a BBL is built
- Borough (1 digit): 1 = Manhattan, 2 = Bronx, 3 = Brooklyn, 4 = Queens, 5 = Staten Island.
- Block (5 digits, zero-padded): a contiguous parcel bounded by streets. Block numbers reset within each borough — block 01234 in Manhattan is a different place than block 01234 in Brooklyn.
- Lot (4 digits, zero-padded): a sub-parcel within a block. Numbering convention: 1–999 are typical fee-simple tax lots, 1000–7999 are condominium unit lots (each condo unit gets its own BBL), 8000+ are special-purpose lots like air rights or public right-of-way.
New York City has roughly 1.05 million tax lots, and BBL is the joining key across NYC DOF, HPD, DOB, City Planning, ACRIS, and NYC 311. Without BBL, joining records across agencies would mean fragile address matching — one building can have multiple addresses, the same address can be spelled differently in different agency systems, and address parsing breaks on edge cases like ambiguous street numbers and missing borough qualifiers. BBL avoids all of that.
A few traps. Condominium BBLs need careful handling: a 50-unit condo might have one parent lot (e.g., 3012340001) and 50 unit BBLs (3012341001 through 3012341050), and operations meant to apply to the building as a whole need to be applied at the parent-lot level. Some buildings span multiple BBLs — large complexes, NYCHA developments, and certain mixed-use parcels are common examples. And BBLs change over time when lots are merged, split, or condo-converted; NYC City Planning publishes a quarterly BBL-change mapping in PLUTO.
Looking up a BBL: NYC DOF’s property tax search at https://a836-pts-access.nyc.gov accepts either a BBL or an address and returns the same record. NYC City Planning’s ZoLa map (https://zola.planning.nyc.gov) is the visual equivalent — click any parcel on the map and the BBL appears in the side panel.
BBL vs. BIN
A related identifier worth knowing about: BIN, the Building Identification Number, is a 7-digit code assigned by NYC City Planning to each individual building rather than to the underlying tax lot. A single BBL can contain multiple BINs when more than one structure occupies the same tax lot, and a single BIN can sit across multiple BBLs in unusual cases. NYC DOB and FDNY records are typically keyed by BIN. NYC HPD records and DOF assessments are typically keyed by BBL. Cross-agency analysis often requires both keys, joined through the PLUTO BBL-to-BIN crosswalk that NYC City Planning publishes as part of the PLUTO and BIN datasets.
What MetroDeeds does with this
A BBL on its own is a handle. It identifies a tax lot, but it carries no information about what is at that address, who owns it, who manages it, how many units it has, or what its violation history looks like.
MetroDeeds keys virtually everything by BBL. The deed feed pulls PLUTO attributes — building class, year built, residential and commercial unit counts, lot dimensions, assessed value — and joins them to every ACRIS deed under that BBL. The detail panel for any deed exposes the BBL alongside the last sale, mortgage status, owner of record, and HPD violation count for that property. Landlord-intel pages at /landlord-intel?bbl=… show the full property profile keyed off a single BBL.
Beyond the single-property view, BBL is the joining key the operator-rollup pipeline uses every night. A BBL is matched to an HPD registration; the registration’s head officer or corporate-owner name becomes the operator; that operator’s confirmed BBL set is the portfolio surfaced on the Landlord Ripoff Watch. Without BBL as a stable joining key, the entire portfolio attribution layer would have to fall back on fragile address matching.
BBL display in the deed feed is a Scout+ feature — at the no-account, free, and Scout tiers the deed table shows the address but redacts the underlying BBL, both to keep the entry-level experience focused on addresses people recognize and to slow low-effort scraping. At Scout+ and above, every deed exposes its BBL.
Frequently asked
How do I find the BBL for an NYC address?
NYC DOF’s property tax search at https://a836-pts-access.nyc.gov accepts either a BBL or an address and returns the BBL alongside the assessment record. NYC City Planning’s ZoLa map (https://zola.planning.nyc.gov) is a graphical equivalent — click any parcel on the map and the BBL appears.
What is the difference between a BBL and an address?
A BBL is the agency-level unique identifier for a tax lot. An address is a display label that can change over time, can be ambiguous, and can map to multiple BBLs (in large buildings) or to no BBL at all. BBL matching is exact; address matching is fragile.
Are condominium units each their own BBL?
Yes. Each condo unit gets its own sub-lot — typically lot numbers 1000 and above — and therefore its own unique 10-digit BBL. The parent lot of the building has a separate BBL.
Do BBLs ever change?
Yes. Lots can be merged, split, or converted to condo. NYC City Planning publishes a quarterly mapping of BBL changes in PLUTO. Long-running portfolios usually accumulate a small number of BBL transitions over time.
Why does MetroDeeds key everything by BBL?
Because BBL is the joining key across every NYC agency that publishes property data. Address matching is fragile and BBL matching is exact, so portfolio rollups and cross-agency joins use BBL throughout.