# Understanding parcel & property identification This article will explain how properties in Cook County are uniquely identified using PINs and how we source and manage the PINs that appear in Property Finder and Property Report. ## What is a PIN? A Parcel Index Number or Permanent Index Number is a 14-digit string that identifies a unique property for taxing purposes. Chicago Cityscape often uses the word "parcel" to mean a property's legal boundary (a single condo unit would be considered a "parcel" by this definition since it represents a unique taxable property even if it shares a building footprint with several other condo units). A "property" may be composed of multiple parcels, with each parcel having a separate PIN. The property with one or more property may have one or more buildings, too! ### A note about addresses The vast majority of PINs have an associated street address, but this street address is there for the reader's convenience and does not perfectly locate a property. The legal description that is written and filed when a parcel is created (or modified) has more meaning to the various Cook County taxing agencies (Treasurer, Assessor, Board of Review, and Clerk). Chicago Cityscape uses [Cook County parcel GIS data](https://hub-cookcountyil.opendata.arcgis.com/search?q=parcel) to locate PINs and parcels, display them on a map, and find nearby data points (like building permits in Chicago, incentives, and Surrounding Places). ### Important characteristics of the PIN #### PINs aren't numbers First, the PIN is not really a number! When using PINs in spreadsheet applications and databases, always treat the PIN as text. This is because some PINs start with "0" and numbers start with "0". If you input the PIN 02063010040000 (which is a commercial building in Barrington) into a spreadsheet application and the column is set to be formatted as containing numbers, then the application will erase the leading "0" and the PIN will no longer refer to any real property. #### PIN patterns In Cook County, the 14 digits are divided into five groups, separated by a hyphen. [Read about the meaning of the pattern](https://www.cookcountyclerkil.gov/property-taxes/about-property-index-number-pin). #### Every PIN is associated with a property class The purpose of a PIN is to uniquely identify a property that can be assessed a property tax. Assessments are based, in part upon comparing similar properties. The Cook County Assessor's Office, like assessors around the country, assigns properties a "class" (or classification). [Review a list of all of the property classes used in Cook County](/guides/propertyclasses.php). Chicago Cityscape relies on property classes to make it easy to find specific types of properties in [Property Finder](/propertyfinder.php). #### Certain PINs represent condos Most people working with PINs should be able to recognize at least one aspect of the pattern: The last four digits indicate if the PIN represents a residential or commercial condo. Every PIN that represents a condo will have numbers other than "0000" in the last four digits. - 02-06-301-004-0000 - Property class: 5-17, property description: One story commercial building - 20-12-101-024-1002 - Property class: 2-99, property description: Residential condominium - 14-18-212-037-1353 - Property class: 5-99, property description: Commercial condominium unit ## How does Chicago Cityscape know which PINs are valid? Every year we request and obtain a list of "active" PINs from the Cook County Treasurer. The Treasurer is responsible for tabulating each property's tax owed to Cook County based on data provided to it by the Cook County Assessor, Cook County Board of Review, and the Cook County Clerk. After the end of the tax year (which coincides with the calendar year), we request a list of the PINs that the Treasuer keeps in its database. The list of PINs changes each year; no new land is created but parcels are divided or combined and new PINs are assigned to these parcels. We keep a record of inactive PINs so that our members can see the ownership or taxing history of properties. We do not have data on the chain of events (the connection between parent PINs and their divided children, or the divided PINs combined into a new parent). Property Finder has a filter to ensure that the results show only recently active PINs. See *screenshot 1*.  *Screenshot 1 showing a filter for a property's assessment status* Property Finder also has a tax exempt filter, which can be used to hide those parcels that are not billed, or to show only those properties that are not billed. Learn more about [[Tax-exempt properties]]. # Related articles - [[PIN Mapper]]