How to Appeal Your Property Tax Assessment

A property tax bill has two parts: the assessed value of your property and the tax rate applied to it. In most places, you can appeal the assessed value if you believe it is wrong, but you generally cannot appeal the tax rate, which local governments set separately. The process below is the common pattern across U.S. counties, illustrated with two counties' own published guides, but the deadlines, forms and appeal levels are set locally, so confirm the specifics with your own county assessor.

Step 1: Read your assessment notice carefully

Idaho's Bonneville County explains that the assessment notice tells you what information the county has about your property, and that it is not a bill and does not tell you what your bill will be. Its guidance is direct: if changes need to be made, you must contact the assessor's office before the deadline printed on the notice, because by the time the tax bill arrives, it is too late to change the assessment. That timing detail catches many homeowners off guard, since the assessment notice often looks less urgent than a bill.

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Step 2: Check your property's record

Your county keeps a record of the details used to calculate your assessment, commonly called a property record card, including square footage, room counts, lot size and year built. Illinois's Will County Board of Review guidance for its appeal process advises reviewing this card and checking it against reality, since a factual error, such as an incorrect square footage, is often the most straightforward basis for correction. Will County's guide notes that copies of the original property record card must be used as evidence when submitting an appeal.

Step 3: Gather comparable sales

The core of most appeals is comparable sales evidence: recent sale prices of similar homes near yours. Will County's guide describes the assessor's process as determining market value from valid sales in the area, excluding foreclosures and short sales, and then applying that method to figure out your assessed value. Bonneville County describes the assessor's office as defending values using current sales information of comparable properties, adjusting for differences between your home and the comparables. Turning that around: your own comparable sales, adjusted honestly for differences, are what an appeal is built on.

Step 4: Talk to the assessor first

Both counties' guidance points toward starting with a conversation rather than jumping straight to a formal hearing. Will County's guide suggests that simply talking with your local assessor will often clear up issues, and notes that assessors are usually very busy right after notices are published, so it is worth reaching out promptly rather than waiting. This informal step can resolve a straightforward factual error without a hearing.

Step 5: File before the deadline

Deadlines are strict and vary by jurisdiction. Will County's guide gives an example of 30 calendar days from the date of the assessment notice to file with the county Board of Review, and states plainly that failing to file within that window forfeits the right to appeal for that cycle. Treat any deadline printed on your own notice as final, and do not assume an informal conversation with the assessor extends it unless your county explicitly says so.

If the informal step does not resolve it

Most counties provide a formal path beyond the informal review, typically a Board of Review or Board of Equalization hearing, and in some states a further appeal to a state tax commission or the courts. Each level generally requires more formal evidence than the last, so an owner who prepares strong comparable sales for the earliest, informal stage often resolves the matter without ever reaching a hearing.

How this connects to your budget

A successful appeal lowers your assessed value and, with it, your property tax bill going forward, which is one line in the broader picture of homeownership costs. See our guide to budgeting for home maintenance for how property taxes fit alongside other recurring costs, and our property tax calculator to see how a change in assessed value or rate affects your estimated bill.

Your takeaway: check your assessment notice for the deadline the moment it arrives, pull your property record card to check for factual errors, gather a handful of genuinely comparable recent sales, and call your assessor's office before you file anything formal.