---
title: "How We Source NYC Property Tax Data"
description: "The City files behind every property tax table on this site, the exact math we use to get from an assessment to a bill, and the places where our figures are estimates."
url: "https://realestaterebatesnewyork.com/nyc-property-tax-data-methodology"
source: "Real Estate Rebate Team"
---

Real Estate Rebate Team


Licensed Broker NY & NJ · License: 10491211335


Data Methodology
# How We Source NYC Property Tax Data


Every property tax table on this site is built from the New York City Department of Finance assessment roll. That is 163,065 rows covering 11,218 tax lots and the years 2010 through 2026. We do not buy this data from an aggregator and we do not estimate the figures ourselves. This page says which City files each number comes from, the exact arithmetic between an assessment and a bill, and the two places where what we show is an estimate rather than a published fact.

## Which City files we read

DOF does not publish one continuous file going back to 2010. The roll is split across four datasets with different formats, and we read all four so the history does not stop at whichever year the current file happens to begin. Each year comes from exactly one of them.
New York City Department of Finance datasets used, by yearDatasetYearsRowsWhat it providesProperty Valuation and Assessment Data (PVAD)2022 to 202651,970The current assessment roll. Carries assessed and billable values, the tax class, exemptions and the tax rate for each lot.PVAD prior-year file20219,813The same roll for the year before the current file's coverage begins, published by DOF as a separate extract.DOF assessment roll archive2019 and 202018,926Archived rolls for the two years that sit between the condensed file and PVAD.DOF condensed assessment roll2010 to 201879,519The historical roll. Carries assessed and billable values, but not the land and additions split for every year, which is why those cells are blank on older rows.

## How we know which tax lot is your apartment

A tax lot is identified by its BBL, the borough-block-lot number the City assigns. Matching an apartment to the right BBL is where most of the errors in property data get made, so we use the City's own records rather than inferring it from an address.
- ACRIS property legals, 4,870 lots. For condos, the City's own deed records name the tax lot for each apartment. We match on that record rather than guessing from the unit number.
- Building BBL, 6,348 lots. For co-ops, townhouses and single-lot properties there is one lot for the whole address, so the building's own BBL is the lot.


## The arithmetic between an assessment and a bill

This is the part other listing sites get wrong, and it is worth being precise about because the two numbers can differ by a lot.

The headline figure in our Tax Assessment column is the assessed value on the City's roll. It is the same number Zillow, Compass and Realtor print, and showing anything else would make our tables look wrong next to theirs. But the City does not calculate your bill from it. For tax classes 1, 2A, 2B and 2C, New York phases assessment changes in gradually, so the billable value lags the assessed value, sometimes by 11 to 17 percent. The City then subtracts any exemption the owner holds, applies the class rate, and subtracts any abatement.

The lag runs both ways. When an assessment falls, the billable value catches down slowly and can sit above the assessment for a few years. That is normal and it shows up on our older rows, so we display both figures rather than only the one that makes a tidier story.
- Assessed value is what the City says the property is worth for tax purposes. We show it, and where a cap applies we show the billable value in its own column beside it.
- Billable value is the capped figure the bill is actually computed on.
- Taxable value is the billable value minus any exemption. An exemption applies on about 37 percent of the rows we hold.
- Property tax is the taxable value multiplied by that year's rate for the property's tax class.
- Net tax subtracts any abatement. Where one applies, our Property Tax column shows the figure after it and says so in the cell.


We checked this chain against 3,000 published rows and it reproduces the City's own tax figure on every one of them. If you compare our number against a DOF notice and it differs, we want to know.

## Combined apartments

Knocking two apartments together does not merge their tax lots. The City keeps assessing them separately and sends a bill for each. Central Park Tower #77-EW is a single home on lots 1220 and 1221, and reading either lot on its own shows roughly half of its real  $219,475 2025 bill.

We add the parts together and label the table with how many lots the home is. 51 of the homes we cover are affected. If a figure is missing for one part in a given year, we leave that year out rather than publish a total that is quietly short.

## Co-ops

A co-op is one tax lot for the whole corporation. There is no per-apartment assessment and no per-apartment bill, because the corporation pays a single bill and recovers it through shareholders' maintenance. So we put the full table on the building page, where the figures belong, and give each apartment page one line and a link to it.

We do not divide a building's bill by its apartment count to invent a per-unit number, and we never print the corporation's total under a single apartment's heading. At 185 West End Avenue that total is over $4.9 million across 432 apartments, and shown without context it is simply a wrong number.

## Where our figures are estimates

Two places. Both are marked on the table itself rather than buried here.

### Tax rates the City has not adopted yet

The City sets rates annually, and it does so after the assessment roll is published. For the most recent years the roll exists but the rate does not, so we carry the prior year's rate forward and calculate from that. Any rate produced this way carries an Estimated marker in its cell, and the table says which fiscal years are affected. Every rate without that marker is the rate the City published.

### Years the City published nothing

Occasionally a lot is missing from a roll it should appear in. Rather than skip the year, which makes 2013 look like it follows 2011, or leave the row blank, which reads as a bill of zero, we keep the year in sequence and say the City did not publish data for it. This affects about 1 percent of properties.

A table that starts in 2019 is a different thing and is not flagged. That is a lot which did not exist before then, usually a new condo or a recent subdivision.

## What these numbers are not
- They are not an appraisal. Assessed value is a tax figure, not a market valuation.
- DOF also publishes a market value, which it derives from comparable rental buildings. For condos it can sit far below what a unit actually trades for, so we do not display it at all.
- They are not a prediction of your bill. Exemptions and abatements attach to the owner and the property, and several do not transfer to a buyer. Rates change annually.
- They are historical record, not advice. For a decision that turns on the number, check the property on the [Department of Finance](https://www.nyc.gov/site/finance/property/property-tax-bills.page) site.


## How often it updates

We refresh from DOF when a new roll is published, which is typically in January for the tentative roll and May for the final one. Rates are picked up when the City adopts them, and the Estimated markers come off the affected years at that point.

Found a figure that disagrees with your DOF notice? Tell us which property and which year and we will trace it.
[Get in touch](https://realestaterebatesnewyork.com/contact)


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