Winnebago County, Illinois Property Tax Appeal Guide
A Winnebago County property owner should first raise a suspected record or valuation problem with the township assessor and, if still dissatisfied, file a formal complaint with the Board of Review by the township's September 4 or September 5, 2026 deadline. FairPath can help organize the notice, property facts, owner-selected comparisons, condition records, and filing checklist. It does not file or represent the owner.
Assessment context: Winnebago County's process has several levels. Township assessors maintain and can correct assessments while they still hold the books; the county Supervisor of Assessments publishes notices and supports assessment administration; the county Board of Review hears timely formal complaints. If an owner remains dissatisfied after the Board decision, the Illinois Property Tax Appeal Board is a separate later route. The county explains that 2023 was its general assessment year and that 2026 is an intervening year, when publication and mailed notices may focus on parcels changed by the township assessor. Even so, the owner should monitor the official publication and verify the current PIN, township, property description, assessment, and any equalization effect before deciding whether a formal complaint is appropriate.
Filing process: Begin with the current assessment record and contact the township assessor promptly, while recognizing that informal review does not replace the Board complaint. Confirm which publication group contains the property, use the current 2026 complaint form, and follow its signature, copy, evidence, and delivery requirements. The Board and Supervisor of Assessments are located at 404 Elm Street, Room 301, Rockford, Illinois 61101. Keep a complete submission copy and dated proof of timely filing.
Evidence to review: The current county Board page links a residential Comparable-Property Grid Sheet and a Sales Locator Tool, signaling that comparisons should be structured rather than submitted as an unexplained address list. For a market-value claim, identify relevant arm's-length sales and compare location, living area, age, style, construction, lot, basement, garage, improvements, and condition. For inequity, compare current assessments of truly similar properties using a consistent metric. Dated photographs, measurements, surveys, permits, repair records, or inspection material can support a physical-data or condition difference when labeled and tied to the claimed correction. Verify the permitted valuation period, number of comparables, copy requirements, and group-specific evidence deadline against the posted 2026 form.
Current deadline guidance: September 4 or September 5, 2026, depending on township. The first 2026 publication group—Cherry Valley, Durand, Laona, Owen, and Rockford—closes September 4. The second group—Burritt, Harlem, Harrison, Pecatonica, Rockton, Roscoe, Seward, Shirland, and Winnebago—closes September 5. Confirm the property's township and the current Board page before filing.
The county now publishes two 2026 groups. Cherry Valley, Durand, Laona, Owen, and Rockford close September 4; Burritt, Harlem, Harrison, Pecatonica, Rockton, Roscoe, Seward, Shirland, and Winnebago close September 5.
The county describes 2023 as the general assessment year, with every fourth year following that cycle. In intervening years such as 2026, publication and notices may apply to parcels changed by the township assessor. Owners should review the current property record and publication instead of assuming every parcel receives the same notice treatment.
The county provides separate residential and commercial or industrial comparable-grid links plus a Sales Locator Tool. A homeowner should use the residential grid applicable to the current 2026 rules, verify all source facts, and explain why each selected property is comparable. Tool output alone is not an argument.
Supplemental evidence deadlines differ by publication group and by the requested reduction. Use the current 2026 form and Board instructions rather than carrying forward an earlier year's paper-copy count or evidence period.
Official filing authority: Winnebago County Board of Review. https://wincoil.gov/departments/supervisor-of-assessments/board-of-review
Source: Winnebago County Supervisor of Assessments, Board of Review, https://wincoil.gov/departments/supervisor-of-assessments/board-of-review. Reviewed 2026-07-29.
Source: Winnebago County, Supervisor of Assessments, https://wincoil.gov/departments/supervisor-of-assessments/. Reviewed 2026-07-29.
Source: Winnebago County Supervisor of Assessments, Property Assessment Frequently Asked Questions, https://wincoil.gov/departments/supervisor-of-assessments/faqs. Reviewed 2026-07-29.
Source: Illinois Department of Revenue, Property Assessment Appeals, https://tax.illinois.gov/localgovernments/property/appeals.html. Reviewed 2026-07-29.
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