BlockLot

Learn NYC property

Every term you meet in New York City property, explained from zero — what it is, how it is worked out, who is responsible, and where to check it. Each page is written by BlockLot from the City's and the State's own publications, with live figures from public data.

Learning how to use BlockLot itself? See the Tutorials.

Agencies and the basics

Who keeps which record, and the numbers that identify a building.

  • Department of Buildings (DOB) — What New York City's Department of Buildings does, how a building permit works from filing to sign-off, what a Certificate of Occupancy is, and how DOB violations and stop work orders are issued and cleared.
  • BlockLot Intelligence: how our figures are made — Where the live counts and timeframes in BlockLot's guides come from — the public records they are computed from, how often they are refreshed, how a waiting time is measured, and what the numbers can and cannot tell you.

Value and property tax

How the City values a property, how the tax is worked out, and what an owner owes.

  • Market value (NYC property tax) — What the Department of Finance's "market value" is, why it is not what a property would sell for, how DOF estimates it for each tax class — with the income formula — and how and when an owner can challenge it.
  • Assessed value and how the NYC property tax is calculated — How New York City turns a market value into a tax bill — the four tax classes, the 6% and 45% assessment ratios, the yearly caps and five-year phase-ins, exemptions and abatements, the tax rates — worked through on a real building.

Violations and enforcement

How violations are issued, what their classes mean, and how they close.

  • HPD violations: Class A, B, C and I — What HPD housing violations are, what Class A, B, C and I mean, how long an owner has to fix and certify each, how a violation is closed or dismissed, and what happens when a Class C is ignored.

Rent regulation and tenant protection

Rent stabilization, harassment rules and the programs that tie them to buildings.

  • Certification of No Harassment (CONH) — What a Certification of No Harassment is, which buildings need one and for what work, how HPD investigates, what happens if harassment is found — and why the program became permanent in 2026.

A–Z

Every term these pages explain, including the names it goes by.