Cook County Assessor's Office

What Cook County Assessor's Office does

The Cook County Assessor's Office is the constitutional government agency responsible for establishing fair market value assessments on approximately 1.8 million parcels of property across Cook County, Illinois. Headquartered at 118 North Clark Street in Chicago and led by an elected Assessor (Fritz Kaegi since 2018), the office operates under a triennial reassessment cycle that systematically covers one-third of the county each year across its 36 townships. It delivers property assessments, exemptions, appeals, omitted-assessment corrections, and tax incentive programs to residential homeowners, condo owners, multifamily developers, and commercial/industrial property owners, and serves a linguistically diverse population through materials in six languages.

The office's core technical capability is its Computer Assisted Mass Appraisal (CAMA) system, which uses multiple regression statistical modeling to value residential properties at scale. The system analyzes property characteristics—land, location, building square footage, construction type—alongside 3–5 years of prior sales data, testing hundreds of model variants to identify the most accurate for fair market value estimation. Condo valuation uses a percentage-of-ownership allocation tied to a building-level total value model. Notably, the office has open-sourced all residential and condo valuation code on GitHub (ccao-data), published models and results on the Cook County Open Data Portal, and offers a Data Subscription service for professional users. Supporting digital channels include an online appeals portal, exemption filing tools, interactive data dashboards, a property tax rate simulator, and 14/10/8-digit PIN property search.

As a government agency, the office does not generate commercial revenue; core assessment services are provided at no cost. Nominal filing fees apply to certain incentive applications (e.g., $750–$1,500 for AHSAP, $1,000 for incentive applications). Distribution is multi-channel: in-person service at the main office and 36 township locations, phone support at (312) 443-7550, an online filing portal, multilingual community events (e.g., Racial Equity and Real Estate Conversations, Market Investor Day), and partner-based outreach through multicultural community organizations. A material operational risk was exposed in 2025 when a Tyler Technologies property tax system upgrade malfunctioned, delaying 2025 property tax bills from the usual July deadline to November 14 and contributing to a 16.7% median property-tax increase, with some neighborhoods such as West Garfield Park experiencing 133% increases. The Homeowner Exemption alone delivers an average of approximately $950 in annual savings per eligible homeowner.

Name

Cook County Assessor's Office

Legal name

Cook County Assessor's Office

Website

https://cookcountyassessor.com

Company type

Private

Founded year

1970

Operating status

Operating

Headcount range

101–250 employees

Short description

The Cook County Assessor's Office is a Chicago-based government agency that values 1.8 million property parcels using CAMA statistical modeling, administers exemptions, appeals, and tax incentive programs, and operates across 36 townships on a triennial reassessment cycle.

Ownership category

akta.pro rank

Product category

Property Tax Assessment Services

NAICS

Offices of Real Estate Appraisers (531320)

SIC

Real Estate Agents & Managers (For Others) (6531)

akta.pro primary industry

Real Estate Valuation & Appraisal (BPAHANAC)

akta.pro secondary industries

Residential Property Appraisal (BPAJAKAA), Commercial Property Appraisal (BPAJAKAB)

Keywords

• Property tax assessment
• Mass appraisal valuation
• Property tax exemptions
• Assessment appeals
• Affordable housing incentives

Headquarters

HQ city

Chicago

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2C

Offering type

Services

Cost components

Personnel, Technology or R&D, Operations, Infrastructure, Marketing or Sales

Distribution channels4 records

Marketing channels6 records

Core offering

The Cook County Assessor's Office performs fair market value property assessments for over 1.8 million parcels across Cook County's 36 townships on a triennial reassessment cycle using a Computer Assisted Mass Appraisal (CAMA) system built on multiple regression statistical modeling. Beyond core valuation, it administers property tax exemptions, an Online Appeals Portal, Omitted Assessment appeals, the Affordable Housing Special Assessment Program (AHSAP), and Class-based Incentive & Special Property Programs that reduce assessed values for qualifying developments.

Product overview

The Cook County Assessor's Office provides a unified government property assessment platform centered on mass appraisal valuation of over 1.8 million parcels using statistical modeling (CAMA system). The core offerings include Property Valuation Services, Online Property Search, Online Appeals Portal, Digital Forms Library, Property Tax Exemptions (Homeowner, Senior, Veterans, Disabled, etc.), Omitted Assessment Appeals, Affordable Housing Special Assessment Program (AHSAP), and Incentive & Special Property Programs. Supporting data services include Data Dashboards, Property Tax Rate Simulator Tool, Cook County Open Data Portal, GitHub Open Source Code & Models, Data Subscription Service, and Multilingual Educational Guides. The office operates a triennial reassessment cycle covering north suburbs, south/west suburbs, and City of Chicago, with exemptions auto-renewing for eligible homeowners and online filing available for all appeals and applications.

Differentiator

Problem solved

Functional benefit

Products and services

• Property Valuation Services

Quantifiable outcome

• Average savings of approximately $950 per year per homeowner through the Homeowner Exemption
• +1 more outcomes

Segments4 records

Ideal customer profiles4 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature4 records

Partnerships

One partnership is on record.

• Tyler TechnologiescriticalTechnology or Integration · 1 January 2025Tyler Technologies provided the new property tax system upgrade for the county's property tax offices (treasurer, clerk, and assessor). The system was intended to replace a decades-old mainframe. However, the 2025 implementation experienced significant problems causing cascading delays to property tax bills, with incorrect calculations for some of the county's 1.8 million parcels. The issue resulted in bills being released on November 14 instead of the usual July deadline and record tax increases.

Scale indicators6 records

Recent moves5 records

Expansion highlights5 records

Emerging players

• HouseCanary: HouseCanary provides AI-powered residential property valuation and analytics. As a tech-forward emerging valuation company, it overlaps with Cook County's residential mass appraisal focus and represents a private-sector methodology alternative that could influence public-sector valuation approaches.
• Veros Real Estate Solutions: Veros provides automated valuation and collateral risk management platforms including AVM and mass appraisal tools used by lenders and government agencies. Its technology stack overlaps with Cook County's valuation methodology, particularly for residential and commercial models.

Broad incumbents

• Clear Capital: Clear Capital is a property valuation technology and analytics company serving lenders and government entities with appraisal management and mass valuation products. Its work on residential valuation analytics is directly comparable to the office's CAMA statistical modeling approach.
• Stewart Information Services: Stewart is a title insurance and real estate information services company with valuation and property data offerings. While primarily title-focused, its property valuation services and government-relations expertise make it a broadly comparable incumbent in property information services.
• Black Knight (now ICE Mortgage Technology): ICE Mortgage Technology (formerly Black Knight) is a major real estate technology incumbent providing valuation, origination, and servicing systems. Its property valuation and analytics offerings intersect with the office's appraisal and assessment technology ecosystem.
• CoreLogic: CoreLogic is a leading provider of property data, analytics, and valuation platforms serving lenders, governments, and real estate professionals. While broader than a single county assessor, CoreLogic's mass appraisal and AVM technology overlaps directly with the office's valuation methodology and data needs.

Direct peers

• Maricopa County Assessor's Office: Maricopa County (Phoenix area) Assessor is another large county assessment office using mass appraisal methodology for over 2M parcels. It is directly comparable in scale, technology use, and residential/commercial valuation mix, providing a useful benchmark for Cook County operations.
• Tyler Technologies: Tyler Technologies is the office's critical technology partner providing the CAMA property tax system upgrade. They are a leading provider of mass appraisal and property tax software for county governments, making them directly comparable as the operational backbone technology vendor for similar assessment offices nationwide.
• Los Angeles County Office of the Assessor: LA County Assessor is one of the largest comparable US county assessment offices, valuing millions of parcels with similar mass appraisal methodology, exemption programs, and appeals processes. It represents a direct government peer operating at similar scale with similar scope of residential and commercial valuation.
• Harris County Appraisal District: Harris County Appraisal District (Texas) is a county-level mass appraisal entity covering Houston and surrounding areas. It is directly comparable in function - valuing1M+ parcels using CAMA systems, administering exemptions, and conducting appeals - making it one of the closest governmental peers to Cook County.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat4 records

Key risks5 records

Key highlights6 records

Customer concentration

• Xtwitter.com/AssessorCook
• GitHubgithub.com/ccao-data
• YouTubeyoutube.com/channel/UC9w4Q3ZJyRS5J27eYKSjwZQ
• Facebookfacebook.com/CookCountyAssessorsOffice
• LinkedInlinkedin.com/company/cookcountyassessorsoffice
• Instagraminstagram.com/cookcountyassessor

Revenue estimate

Valuation estimate

Number of profiles

Profiles2 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Cook County Assessor's Office