Assessed Value vs. Market Value: Why Your Home Is Worth Two Different Numbers

You open your property tax bill, squint at the number labeled "assessed value," and wonder why it doesn't match anything you've seen on Zillow. Then someone mentions your home's "appraised value" in passing, and now you've got three different numbers floating around for the same house. What's going on?

Here's the short version: your home has multiple "values" because different people — your local government, the housing market, and a licensed appraiser — are each answering a slightly different question. Conflating them can cost you real money. Either you overpay property taxes for years without realizing you can fight it, or you misunderstand what your house would actually sell for if you listed it tomorrow.

Let's break down exactly what each number means, where it comes from, and why the gap between them matters more than most homeowners realize.

What Assessed Value Actually Means

Assessed value is the number your local government assigns to your property for the sole purpose of calculating your property tax bill. Full stop. It's not what you could sell the house for. It's not what a bank would lend against it. It's a bureaucratic figure produced by your county assessor's office, and it follows rules that vary dramatically from state to state.

Here's how the math typically works. Your county sets a "mill rate" — essentially a tax rate expressed in dollars per $1,000 of assessed value. Then they multiply that rate by your assessed value to get your annual tax bill.

So if your home's assessed value is $320,000 and your local mill rate is 12 mills (that's $12 per $1,000 of value), your annual property tax bill is $3,840.

Simple enough. But here's where it gets weird.

Most counties don't assess your home at 100% of what they think it's worth. They apply something called an assessment ratio — a percentage of the property's estimated full market value. A county with an 80% assessment ratio would assign a $320,000 assessed value to a home they've estimated is worth $400,000 on the open market.

That ratio varies wildly. Some states assess at 100%. Others go as low as 10% or 25%. California's Proposition 13, passed in 1978, famously caps assessed value increases at 2% per year regardless of what the market does — which is why longtime California homeowners often pay property taxes on an assessed value of $200,000 on a house now worth $1.4 million.

What Market Value Actually Means

Market value is simpler in concept, messier in practice. It's the price a willing buyer would pay a willing seller when neither is under any unusual pressure to transact. In theory, it's the number you'd see if you listed your home today and let the market decide.

In practice, market value is an educated estimate. Real estate agents use comparable sales — "comps" — to arrive at a number. A licensed appraiser does something more formal and more systematic, factoring in the home's condition, square footage, lot size, local inventory, and recent sales of similar homes nearby. Banks require that formal appraisal before they'll fund a mortgage.

Market value moves constantly. A house is worth more in a low-rate environment when buyers have more purchasing power. It's worth less when rates spike and monthly payments become punishing. When the Fed raises rates aggressively — as it did in 2022 and 2023 — market values often drop even when nothing about the house itself has changed. We've seen exactly that dynamic play out as Treasury yields push deeper into uncomfortable territory, squeezing what buyers can actually afford and, by extension, what sellers can realistically charge.

Assessed value, by contrast, moves slowly. Assessors typically revalue properties on a set schedule — sometimes annually, sometimes every three to five years — and they use lagged data. So assessed values often trail market values significantly in a fast-moving market, and they sometimes overshoot when values correct.

The Gap Between Them — And Why It Can Be Expensive

The difference between assessed value and market value isn't just an academic footnote. It has direct financial consequences.

When assessed value is too high relative to market value, you're overtaxed. You're paying property taxes on a number that doesn't reflect economic reality. This happens a lot after markets correct. A homeowner might have bought at the peak and seen their market value fall 15%, but their assessed value — set before the correction — hasn't caught up yet.

When assessed value is too low, you're getting a tax break the government may not have intended to give you. This is common in states with strong assessment caps (California being the classic example) or in areas where assessors simply haven't kept pace with a hot market.

The tricky part is that most homeowners don't know they can appeal their assessment. They receive the bill, assume the number is correct, and pay it. The appeal process exists in every county in the country. You typically have a limited window — often 30 to 90 days after your assessment notice arrives — to file a formal challenge with evidence that the assessed value is too high. Evidence usually means recent comparable sales showing what similar homes actually sold for.

A Quick Look at How the Numbers Stack Up

Here's a simplified example of how assessed value, market value, and property taxes interact across a few different assessment structures:

Historical Context: When the Gap Got Really Ugly

The 2008 financial crisis is the most dramatic recent example of assessed and market values getting badly out of sync. Home prices fell 30% to 50% in markets like Phoenix, Las Vegas, and parts of Florida between 2007 and 2011. But municipal governments — desperate for revenue during the recession — were slow to lower assessed values. Homeowners were stuck paying taxes on values that no longer existed.

A Phoenix homeowner who bought in 2006 at $280,000 might have seen their market value fall to $160,000 by 2010 — a 43% drop. But if their county assessed value was still sitting at $240,000, they were paying taxes on $80,000 of phantom equity. Thousands of homeowners in those markets successfully appealed their assessments, but most didn't bother.

The reverse happened during the post-pandemic boom. Market values in many Sun Belt cities jumped 40% to 50% between 2020 and 2022. Assessed values lagged behind, giving homeowners a temporary tax cushion. But that cushion eventually disappeared as reassessments caught up — and in some cases, property tax bills nearly doubled within a few years.

What About Appraised Value? (Yes, There's a Third Number)

Since we're already juggling two values, let's get the third one out of the way.

Appraised value is an estimate of market value produced by a licensed appraiser — usually at a bank's request when you're buying or refinancing. It's the lender's protection against overpaying for collateral. The bank won't lend you $400,000 on a house an appraiser says is only worth $350,000. You'd have to either come up with the difference in cash, renegotiate the purchase price, or walk away.

Appraised value and market value are often close to each other but not identical. A seller might believe their home is worth $425,000 based on a neighbor's recent sale. The appraiser might come in at $395,000 using a stricter methodology. That $30,000 gap can kill a deal — or at least complicate it.

None of these three numbers — assessed, market, appraised — is necessarily "wrong." They're just answering different questions for different audiences.

How Rising Interest Rates Scramble All of This

Here's where things get particularly interesting for homeowners in 2025 and 2026.

When mortgage rates rise sharply, market values feel the pressure first. Buyers can afford less when their monthly payment on a $400,000 mortgage jumps from $1,900 to $2,600. So sellers have to lower asking prices to find qualified buyers. Market value adjusts, sometimes within months.

Assessed value adjusts on a much slower clock. That mismatch creates exactly the kind of over-assessment problem I mentioned above — homeowners paying taxes on values that the market has already marked down.

The credit squeeze driven by elevated bond yields doesn't just affect Wall Street. It feeds directly into the housing market through mortgage rates, which then feed into market values, which then create that lag between what your home is actually worth and what your county thinks it's worth for tax purposes.

If rates have moved significantly in your area and home prices have softened, that's exactly when it makes sense to dig into your assessment and consider whether an appeal is warranted.

How It Affects You Right Now: A Practical Checklist

Here's what to actually do with this information.

Step 1: Find your assessed value. Your county assessor's website almost always has a public lookup tool. Search your address and find both your assessed value and the assessment ratio your county uses.

Step 2: Back-calculate the implied market value. If your assessed value is $300,000 and your county uses an 80% assessment ratio, the county is implying your home is worth $375,000. Does that match reality?

Step 3: Pull recent comps. Look at what similar homes in your neighborhood have actually sold for in the past six months. Zillow, Redfin, and your county's own sales records all have this data. If comparable homes are selling for $310,000 and your implied market value is $375,000, you have grounds for an appeal.

Step 4: Know your appeal window. This is the part most people miss. Every county has a deadline. Missing it means waiting another year or more for another shot.

Step 5: Factor this into refinancing math. If you're thinking about a cash-out refinance, what matters to the bank is appraised value, not assessed value. Don't be surprised if those numbers differ significantly.

The broader economic environment matters here too. In a world where mortgage rates remain stubbornly elevated and household budgets are already stretched, an unnecessary overpayment on property taxes isn't a rounding error — it's real money that compounds every year you don't address it.

FAQ

Is assessed value always lower than market value?

Usually, but not always. In most states, assessed value is a percentage of market value — so by design, it's lower. But in jurisdictions that assess at 100% of market value, or when markets have recently declined faster than reassessments have caught up, assessed value can actually be higher than what you'd realistically sell for. That's the scenario where appealing your assessment makes the most financial sense.

Can I use my assessed value to figure out what my home is worth?

Not reliably. Assessed value is a tax administration tool, not a valuation tool. To get a reasonable estimate of what your home would actually sell for, you'd want to look at recent comparable sales in your neighborhood or pay for a licensed appraisal. What you're really asking in that case is about market value — and for that, the assessed value is often years behind.

How do I appeal my property tax assessment?

Visit your county assessor's website and look for the appeals or "equalization board" process. You'll typically need to file within a set window after your assessment notice is mailed — often 30 to 90 days. Your strongest evidence is a list of comparable sales showing that similar homes sold for less than what your assessment implies. Some counties allow informal reviews before a formal appeal, which can resolve the issue faster.

Does my assessed value affect my mortgage or refinancing?

Your property tax bill — which is based on assessed value — does affect your mortgage indirectly, because lenders require that taxes be included in your monthly escrow payment. Higher assessed value means higher taxes means higher monthly housing cost. But the bank's lending decision is based on appraised value, not assessed value. Those are two entirely different numbers produced by two entirely different processes.

Why does California have such a strange property tax system?

California's Proposition 13, passed by voters in 1978, caps annual assessed value increases at 2% per year and resets the assessment to purchase price only when a property is sold. The idea was to protect longtime homeowners — especially retirees on fixed incomes — from being taxed out of their homes during rapid appreciation. In practice, it means a homeowner who bought in 1995 might pay taxes on an assessed value of $180,000 on a house now trading at $1.2 million, while their new neighbor pays taxes on that full $1.2 million. It creates enormous disparities and is frequently debated in California politics.