Co-op and condominium in the record

The difference the record cares about

A condominium apartment is real property. It has its own tax lot, its own deed and its own mortgage. A co-operative apartment is not real property at all: the corporation owns the building, and a purchaser buys shares allocated to an apartment together with a proprietary lease of it. Everything else about how the two behave in the City's files follows from that one distinction.

A condominium: many lots, one billing lot

When a condominium is declared, the Department of Finance issues each apartment its own tax lot number, usually starting at 1001. For billing it also creates a single billing lot, usually numbered from 7501. PLUTO, the file that describes the physical building, carries the billing lot: one row, with the whole building's area, storeys and unit count. ACRIS, by contrast, records each apartment's deed against that apartment's own unit lot.

So the two files describe the same building with different keys, and joining them naively produces a condominium page with no sales on it at all.

A co-operative: one lot, many share transfers

A co-operative has one tax lot for the entire building. Individual apartment sales are recorded against that single lot, identified only by the unit designation typed on the form, and the instrument is a Real Property Transfer Tax return rather than a deed. A large pre-war co-operative therefore shows dozens of transfers against one lot, each with a unit label like 14B or 6/7C in the record's own formatting.

How this site puts the two back together

The Digital Tax Map publishes the condominium crosswalk: every unit lot, the condominium it belongs to, and that condominium's billing lot. This site loads that crosswalk first, then reads every residential transfer in ACRIS and resolves the lot it names either directly to a building or through the crosswalk to the billing lot PLUTO describes. Co-op transfers need no crosswalk, because the lot they name is already the building.

What that means when you read a page

• On a condominium page the unit column holds the designation as filed, and prices are for real property.
• On a co-operative page every price is for shares. A co-op corporation may carry a mortgage on the building itself, which no share price includes, so co-op figures and condominium figures are not directly comparable.
• A whole-building transfer appears on both kinds of page and is usually several orders of magnitude larger than an apartment. The property type column distinguishes them.
• A building that converted from rental to co-operative will often show one very large early transfer and then a long series of small ones.