Understanding your property tax assessment

This article is for educational purposes only and is not a substitute for professional advice. Local codes, regulations, and best practices vary by region.

You received your property tax assessment in the mail and you’re not sure if it’s right. The assessed value seems too high. Or way too low. You don’t know how they calculated it, whether you’re allowed to challenge it, or whether it even matters. Property taxes are a substantial part of annual homeownership costs, and they’re also one area where you actually have meaningful control. Most homeowners never use that control.

How Property Tax Assessment Works

Every property is assessed by the county assessor’s office, typically every 1-3 years. The assessor determines the value of your property. This value is multiplied by the local tax rate (expressed as mills per thousand dollars) to calculate your tax bill.

Example: If your house is assessed at $400,000 and the tax rate is 20 mills per thousand, your annual tax is $8,000.

The assessed value is supposed to reflect the fair market value of your property—what it would sell for in an open market. But assessments are often based on limited information, so they’re sometimes inaccurate.

How They Determine Value

Assessors use several methods. For recently sold properties, they often use the sale price as a baseline, sometimes adjusted for improvements or condition. For properties not recently sold, they use comparative market analysis—looking at similar properties that recently sold and adjusting for differences.

They also gather data: square footage, lot size, number of bedrooms and bathrooms, age, condition, whether the house is on a busy street, proximity to amenities, and local market trends. Data is often gathered infrequently, so if your house has changed significantly, the assessment might be out of date.

When Assessments Are Inaccurate

Assessments might be too high if your house has deferred maintenance, significant damage, or features that reduce value but haven’t been accounted for. An assessor might list your house as having a second bathroom when you actually don’t. They might not know about a major repair or upgrade.

Assessments might be too low if comparable sales have driven up values in your neighborhood but the assessment wasn’t updated, or if you made significant improvements that increased value.

Assessments can be uniformly wrong if all properties in a district were systematically misjudged. This happens but is less common because aggregate errors get caught.

Your Right to Challenge

Every state and county has processes for challenging your assessment. The specifics vary, but the general process is: request a copy of your assessment and supporting data, review it for errors, file a formal challenge if you believe it’s inaccurate, and potentially attend a hearing to argue your case.

You have a limited window to file a challenge—often 30-60 days after assessment. Missing the deadline means you wait years until the next assessment.

What You Need to Challenge Successfully

Errors in facts are the strongest basis for a challenge. If the assessment lists 3 bedrooms and you have 2, that’s an error. If it lists square footage that’s wrong, that’s an error. Gather documentation supporting the correct facts.

Comparable sales are also valid evidence. If comparable houses in your neighborhood sold for less than your assessed value, that’s evidence your assessment is high. Get recent MLS data or comparable sales information.

Photos or inspection reports showing deferred maintenance, damage, or missing features can support a claim that your assessment is too high.

Proof of a reassessment or recent market analysis showing your area’s values changed might support a challenge.

The Process

Obtain your assessment and the assessor’s data about your property. Review it for errors. If you find errors in basic facts (bedrooms, bathrooms, square footage), gather documents proving the correct information.

Request information about the assessment methodology and comparable properties used.

File a formal challenge (sometimes called a “Petition to Review” or “Homestead Exemption Appeal”) within the deadline, typically available through your county assessor’s website.

Attend any hearing and present your evidence. Be organized, professional, and specific. Explain why the assessment is wrong and provide supporting evidence.

Wait for a decision. The appeal might be approved (assessment reduced), denied, or partially approved.

Success Rates

Challenges succeed most often when there are clear factual errors (bedrooms, bathrooms, square footage). Challenges based on opinion (“the condition isn’t as good as assessed”) are harder to win.

Many assessments are reduced through challenges because assessor data is often outdated or incomplete. It’s worth attempting, especially if you have evidence of errors or recent market data showing lower comparable sales.

Does It Matter?

Reducing your assessed value by 10 percent might reduce your annual taxes by $800-2,000 depending on your tax rate. Across 10 years, that’s $8,000-20,000. It’s worth the effort, especially if you have clear evidence of an error.

The process typically costs nothing except your time, though some people hire a property tax consultant or attorney to represent them (costs $500-2,000 typically).

Maintaining Your Assessment

Even after a successful challenge, your assessment can go back up. Most areas reassess every few years. If your neighborhood appreciates, your assessment will reflect that.

Keep documentation of improvements and maintain records in case you challenge again. If your area went through significant decline, you might need to challenge multiple times.

Regional Differences

Some areas reassess annually based on market data. Others assess every 3-5 years. Some have homestead exemptions that reduce assessed value for primary residences. Some have caps on annual assessment increases. Rules vary dramatically by location.

Know your local rules. Your county assessor’s website has information about assessment schedules, appeal deadlines, and processes.

The Bottom Line

Your property tax assessment is a number that impacts your annual costs significantly. It’s worth reviewing and challenging if it’s inaccurate. Most people never look at their assessment, much less challenge it. You have the power to do something they don’t.

© The Whole Home Guide