A BBL is the ten-digit number New York City uses to identify one tax lot — a parcel of land. It is built from three parts: one digit for the borough, five for the block, and four for the lot. Almost every city property record is filed against it, which is why it is the number most useful to have when you want a building's history.
Reading one, digit by digit
Take 1008110001, the lot under 463 7 Avenue in Manhattan. It splits like this:
| Part | Digits | Means |
|---|---|---|
| Borough | 1 | Manhattan |
| Block | 00811 | Tax block 811 |
| Lot | 0001 | Lot 1 on that block |
The borough digit is always one of five: 1 Manhattan, 2 the Bronx, 3 Brooklyn, 4 Queens, 5 Staten Island. Block and lot are padded with leading zeros to five and four digits, which is why a BBL is always exactly ten characters even when the block is a small number.
What the city files against it
Here is the actual PLUTO record for that BBL, from the Department of City Planning's property file, with the field names the dataset uses:
| Field | Value |
|---|---|
| bbl | 1008110001 |
| borough | MN |
| block | 811 |
| lot | 1 |
| address | 463 7 AVENUE |
| zipcode | 10018 |
| bldgclass | O4 |
| yearbuilt | 1925 |
| numbldgs | 1 |
| unitstotal | 88 |
One quirk worth knowing if you ever query the data yourself: PLUTO returns the BBL as a number, so it arrives looking like 1008110001.00000000. It is the same ten digits.
A lot is land, not a building
This is the distinction that trips people up. A BBL identifies a parcel. The buildings standing on that parcel each have their own identifier, a BIN. Usually there is one building on one lot and the two travel together. Sometimes there are hundreds: Co-op City in the Bronx sits largely on BBL 2051410120, which PLUTO records as carrying 250 buildings. One BBL, 250 BINs.
Which number you need depends on the record. Ownership, deeds, taxes and assessments are filed against the lot, so they want the BBL. Elevator inspections, boiler filings and facade reports are about a structure, so they want the BIN.
Where to find yours
You do not need to know your BBL to look a building up here — type the address and Check a Building resolves it. If you want the number itself, it appears on your property tax bill, in the city's ACRIS document search, on the Department of Finance's property page, and on the building page of this site under the address.
Why records sometimes disagree about it
Lots get merged and split. When two parcels are combined, one BBL survives and the other stops being used, but older filings still carry the retired number. Condominiums complicate it further: a condo building often has a billing BBL for the whole property plus a separate BBL for each unit, so a search can legitimately return several. None of this is an error in the records — it is what happens when a numbering system outlives the parcels it was drawn for. It is also why matching records to a building takes more than one lookup, which is described here.
Sources: NYC Department of City Planning — PLUTO (64uk-42ks); NYC Department of Finance. Figures above are the live values on the dates queried. This is general information about public records, not legal or financial advice.