A good commercial property manager handles Cook County reassessments as a year-round process, not a once-every-three-years scramble. That means keeping clean income, expense, and vacancy records, tracking the township’s reassessment and appeal calendar, reviewing the Assessor’s value against the building’s actual income, and coordinating with a property tax attorney to appeal at the Assessor, then the Board of Review, and if needed the Illinois Property Tax Appeal Board. The manager then budgets for the result, passes taxes through to tenants as their leases allow, and credits refunds back when an appeal succeeds.
How the Cook County cycle works
The Cook County Assessor reassesses one-third of the county each year on a three-year cycle:
- City of Chicago: 2021, 2024, next in 2027
- North suburbs: 2019, 2022, 2025
- South and west suburbs: 2020, 2023, 2026
Commercial property in Cook County is assessed at 25 percent of the Assessor’s estimate of market value. For income-producing property, the Assessor generally values the building using the income approach: market rent, vacancy, expenses, and a cap rate. That is why a building’s actual income and vacancy are the core of most appeals.
What a property manager does before the notice arrives
The best appeals are built from records kept all year. A manager should maintain:
- A current rent roll and copies of all leases
- At least three years of income and expense statements
- Vacancy history by suite, with dates and marketing activity
- Records of concessions such as free rent and improvement allowances
- Capital improvement records and photos of physical condition
- Any recent appraisal, sale, or purchase price
Illinois law now requires many owners of income-producing property in Cook County to submit income and expense information to the Assessor. The manager typically prepares and files it.
When the reassessment notice comes
Each township has its own appeal window, which is short. The manager should:
- Calendar the Assessor appeal deadline for the township the day values are released.
- Compare the Assessor’s market value with a value based on the building’s actual NOI and a realistic cap rate.
- Compare the assessment with similar buildings nearby for uniformity.
- Send the owner and the tax attorney the numbers, with a recommendation.
The grounds for a commercial appeal
- Overvaluation. The Assessor’s market value is higher than what the building’s income, a recent sale, or an appraisal supports.
- Vacancy. Significant vacancy during the assessment year, documented with rent rolls and vacancy affidavits.
- Lack of uniformity. Similar properties are assessed at materially lower values.
- Condition or obsolescence. Physical damage, functional problems, or an outdated layout that limits income.
The three levels of appeal
- Cook County Assessor. The first appeal, filed during the township’s window after values are released.
- Cook County Board of Review. A separate, independent review with its own township windows, available whether or not you won at the Assessor.
- Illinois Property Tax Appeal Board or circuit court. A further appeal after the Board of Review decision, used for larger or contested cases.
Commercial owners typically work with a property tax attorney, who files the appeal and is paid on contingency in many cases. The manager supplies the data and keeps the deadlines.
Owners should also appeal in the second and third years of a cycle when vacancy or income changes. An appeal is not limited to the reassessment year.
After the appeal: budgets, tenants, and refunds
The first-installment Cook County bill is an estimate based on the prior year. The second installment reflects the new assessment and any appeals. The manager should:
- Budget the likely tax change before the second installment arrives
- Pass taxes through to tenants as each lease allows, through estimates and the annual reconciliation
- Credit tenants their share of any refund, as the leases require
- Explain large changes to tenants early, so a tax increase does not become a lease dispute
Outside Cook County
Lake County, DuPage, and the other collar counties do not use Cook’s triennial cycle. Properties are assessed by township assessors at one-third of market value, with a general reassessment every four years and annual adjustments in between. Appeals go to the county Board of Review and then to the Property Tax Appeal Board. The same record keeping applies.
Need help with a reassessment?
Property taxes are often a building’s largest operating expense, and they directly affect what tenants pay and what the building is worth. Our property management team tracks assessments and appeal deadlines for owners across Cook, Lake, and the collar counties. Learn more about commercial property management at Van Vlissingen and Co. For current market conditions, see the daily-updated RFP Chicagoland Commercial Real Estate Index.
This article is general information, not legal or tax advice. Consult a property tax attorney about your specific property.
Frequently asked questions
How often does Cook County reassess commercial property?
Every three years by region: the City of Chicago, the north suburbs, and the south and west suburbs. The south and west suburbs are reassessed in 2026, and the City of Chicago in 2027.
What percentage of market value is commercial property assessed at in Cook County?
Commercial property is assessed at 25 percent of the Assessor’s estimate of market value.
Can I appeal in a year my property was not reassessed?
Yes. Owners can appeal in any year, which matters when vacancy rises or income falls between reassessments.
What is the difference between the Assessor and the Board of Review?
They are separate offices. The Assessor sets the initial value and hears the first appeal. The Board of Review is an independent body that hears a second appeal with its own deadlines.
Who gets the refund if a commercial tax appeal succeeds?
It depends on the leases. Under most net leases, tenants who paid their share of the taxes are entitled to their share of the refund.