Look up your Nassau or Suffolk County assessment

Both Nassau and Suffolk County publish free, per-parcel assessment pages online. There is no paywall, no login, and no MLS access required — just your address. Placeholder guide; the fully-illustrated version is coming.

Nassau County

The Nassau County Land Records viewer and the Assessment Review Commission give you the parcel's Section-Block-Lot number, assessed value, tax class, and roll year.

Suffolk County

Suffolk County's assessments are managed by the individual towns (Babylon, Brookhaven, East Hampton, Huntington, Islip, Riverhead, Shelter Island, Smithtown, Southampton, Southold). Start from your town's assessor page — for example Town of Islip Assessor.

Statewide records

New York State's Real Property Tax Services portal carries the annual tax rolls for every county in the state, published as CSV downloads.