DOF

The Department of Finance runs the money side of New York City property: it maintains the tax map and assigns every lot its borough-block-lot identity, classifies properties into tax classes, sets market and assessed values, and bills and collects property taxes. Its City Register records deeds, mortgages, and related instruments in four boroughs — Staten Island records with the Richmond County Clerk.

For analysis, DOF records are load-bearing: the lot area most zoning arithmetic divides by is a DOF figure, the building class that summarizes what stands is a DOF classification, and the assessment roll is the closest thing to a citywide inventory of property facts. When a lot-area or floor-area figure looks wrong, the assessment records are where verification starts.