Naperville Property Assessment, Valuation & Appeals

Taxation and Finance Illinois 4 Minutes Read · published February 21, 2026 Flag of Illinois

Property owners in Naperville, Illinois should understand how assessments, valuations and appeals work because local property taxes are based on county assessments and may affect your annual tax bill. This guide explains who enforces assessments, how to request a review or appeal, what forms and documents are typically required, and where to find official rules and contacts to start an appeal.

Penalties & Enforcement

Assessment valuation is performed by the county assessor and reviewed by the county Board of Review; enforcement for inaccurate returns or tax delinquencies is handled by county offices and, for ordinance violations, by the City of Naperville where applicable. Specific monetary fines and daily penalties for assessment misconduct or late tax payment are not consistently listed on the cited pages; see the official county and city pages for details and exact figures. Naperville Municipal Code[1] provides city ordinance text, while county assessor offices provide assessment and payment rules for parcels in DuPage and Will counties described below.DuPage County Assessor[2] Will County Assessor[3]

  • Fines/penalties: not specified on the cited page for municipal ordinances addressing assessment valuation; check county treasurer pages for tax-payment penalties.
  • Escalation: first, repeat and continuing offence procedures are handled per county law or by court order; specific escalation amounts are not specified on the cited page.
  • Non-monetary sanctions: orders to correct records, assessment adjustments, lien recordings, collections and court actions may apply depending on the finding.
  • Enforcer and inspection: the county assessor and county Board of Review handle assessments and appeals; the City of Naperville enforces local ordinance violations when applicable. Use the official county assessor or Board of Review contact pages to file complaints or request inspections.DuPage County Assessor[2]
  • Appeals/review: appeals are filed to the county Board of Review following county deadlines; the exact appeal filing deadlines and procedures are set by the county and are not fully specified on the cited city ordinance page.
  • Defences and discretion: common defences include providing recent sales comparables, repair invoices, permits or evidence of incorrect property characteristics; variances or adjustments require evidence and are subject to Board discretion.
  • Common violations: incorrect assessment data, failure to report improvements, and filing inaccurate exemption claims. Penalties vary by county and are not specified on the cited municipal page.
Appeals must be supported by documentation such as recent appraisals, repair receipts, and comparable sales.

Applications & Forms

County boards typically publish specific appeal or complaint forms on their websites. If a form or numbered application exists it is provided by the relevant county assessor or Board of Review; the Naperville municipal code does not replace county appeal forms.

  • DuPage: appeal and exemption information and any county Board of Review forms are available via the DuPage County Assessor or Board of Review pages.DuPage County Assessor[2]
  • Will: appeal forms and assessor guidance are available on the Will County Assessor site.Will County Assessor[3]
  • City ordinances: for municipal penalties, compliance notices and procedures refer to the Naperville Municipal Code.

How to file an assessment appeal

  1. Confirm which county (DuPage or Will) holds your parcel assessment by checking your tax bill or county parcel search.
  2. Download and complete the county appeal form or submit the required online appeal per the county instructions.
  3. Assemble evidence: sales comparables, recent appraisals, photographs, repair invoices and building permits.
  4. File the appeal with the county Board of Review within the county deadline and pay any required filing fee if specified by the county.
  5. Attend the hearing or provide written evidence; if dissatisfied, review further appeal rights (state-level review or court) per county guidance.
Start appeals early — county deadlines are strict and vary by jurisdiction.

FAQ

Who assesses property values for Naperville addresses?
Property assessments for Naperville addresses are conducted by the county assessor in the county where the parcel lies (DuPage or Will).
Where do I file an appeal of my assessment?
File an appeal with the county Board of Review for the county that assesses your property; see the county assessor/Board of Review pages for forms and deadlines.
Are there municipal fines for assessment disputes?
Assessment disputes are handled by county offices; municipal ordinances may address false statements or local reporting requirements, but specific monetary fines vary and are not fully specified on the cited municipal page.

How-To

  1. Find your parcel and assessor contact on the appropriate county assessor website.
  2. Download the Board of Review appeal form or use the county online filing tool.
  3. Collect supporting documents (comparables, appraisal, receipts).
  4. Submit the appeal before the county deadline and keep proof of filing.
  5. Attend the review hearing or submit evidence as directed by the Board of Review.

Key Takeaways

  • County assessors set values; appeals go to the county Board of Review.
  • Deadlines are set by county — check county pages early.
  • Prepare documentary evidence to support valuation adjustments.

Help and Support / Resources

  1. [1] Naperville Municipal Code - Municode
  2. [2] DuPage County Assessor
  3. [3] Will County Assessor

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