NYC residential sales linked to ACRIS deeds and mortgages, 2016–2025

New York City's sales and land-registry files contain complementary information but share no transaction identifier. Condominium sales are particularly difficult to link because the sales parcel often identifies the building, while deeds and mortgages identify a unit. This dataset connects the sources through documented rules for parcel, amount and date. It retains 729,047 residential sales dated 2016–2025. Among positive-price house and condominium sales in the four boroughs covered by ACRIS, 97.2% of house sales and 96.0% of condominium sales are linked to a deed. Recorded-mortgage indicators use three windows around the sale. Deed-level flags describe possible company buyers, shared surnames, shared mailing addresses and lender acquisitions. Remaining unlinked condominium sales are concentrated at higher prices. The deposit includes source extracts, code, documentation and an offline example. Coverage and administrative-field agreement are reported separately from accuracy, which has not been measured against verified instruments. Revision details are in revision_notes.md.