Assessed value meaning: what it is and why it drives your tax bill

Last updated 2026-07-09

What does assessed value mean on a property tax bill?

Assessed value is the number your local government puts on your property for tax purposes. Multiply it by the local tax (mill) rate and you get your tax bill. It is arithmetic, nothing more. The confusion starts because people use 'assessed value,' 'appraised value,' and 'market value' as if they mean the same thing. They don't.

Here is the clean version. Market value is what a willing buyer pays a willing seller in an arm's-length deal right now. Appraised value is a professional estimate of that market value, produced by the assessor or a licensed appraiser. Assessed value is what the government taxes, and it may equal market value or a fraction of it, depending on your state's rules ^[1].

The International Association of Assessing Officers (IAAO), which sets the standards assessors follow across North America, defines assessed value as 'the value placed on property for purposes of computing the property tax' ^[2]. Read that carefully. It says nothing about what your house would sell for. The assessor is not telling you your home's worth on the open market. The assessor is producing a number that, once combined with a rate, raises the revenue local government wants.

Your bill usually shows at least two lines: assessed value and taxable value. Taxable value is assessed value minus any exemptions you qualify for, like a homestead exemption or a senior freeze. The rate applies to taxable value, not assessed value, so your real bill can land below what the assessed-value line suggests.

How is assessed value calculated?

County assessors set assessed value one of two ways, or a mix of both.

The first way sets assessed value at 100% of market value. The assessor runs a mass appraisal model, feeds in recent sales, square footage, age, and condition data for every property in the jurisdiction, and the model spits out a value. That value becomes your assessed value ^[3]. California is the famous exception here, because Proposition 13 freezes value to a base year, but most 100% states just try to track what homes actually sell for.

The second way applies an assessment ratio. The state or county sets a legal fraction, say 40% in Georgia or 10% for Cook County residential property, and assessed value is that share of market value. If your house is worth $400,000 and the ratio is 40%, your assessed value is $160,000. The rate is set higher to compensate, so the final bill can match a 100% jurisdiction exactly. The ratio changes the math, not necessarily the outcome ^[4].

The ratio stops mattering the moment the assessor gets market value wrong. If your home is worth $400,000 and the model pegs it at $500,000, your assessed value in a 100% state is $500,000 and you are overtaxed by 25%. In a 40% state it reads $200,000 instead of $160,000. Same percentage error, same overpayment.

Mass appraisal is imprecise by nature. IAAO standards say a well-run system should hit a median sales-ratio between 90% and 110%, with a coefficient of dispersion (a uniformity measure) under 15% in most residential markets ^[2]. Plenty of jurisdictions miss those marks. That gap is the reason appeals exist.

What is the difference between assessed value and market value?

They answer different questions. Market value asks what the property would sell for today. Assessed value asks what base the government taxes. Same house, two numbers, and they can be miles apart.

The gap varies enormously by state and even by county. The table below shows assessment ratios and effective ratios for a sample of high-population states, drawn from the Lincoln Institute of Land Policy's 50-State Property Tax Comparison Study ^[5].

State	Legal assessment ratio	Effective ratio (median residential)
California	100% of base year value (Prop 13 capped)	Varies widely by purchase year
Illinois (Cook County, residential)	10% of market value	~10%
New York (outside NYC, Class 1)	Varies by municipality	Often 1 to 3%
Texas	100%	~95 to 100%
Florida	100% (Just Value)	~85 to 95% after Save Our Homes cap
Georgia	40% of fair market value	~35 to 42%
Arizona (residential)	10% of full cash value	~9 to 11%

Sources: Lincoln Institute of Land Policy 50-State Property Tax Comparison Study ^[5]; individual state statutes ^[4].

That gap can help you or hurt you. When a hot market pushes sale prices up faster than the assessor's model catches up, your assessed value sits below market value. Fine by you. When the model overshoots, your assessed value tops what a fair appraisal supports, and you pay more than your share.

Here is the part that trips people up. A high assessed value does not automatically mean a high bill. Local governments set the rate to raise a fixed amount of revenue. When assessed values rise across the board, rates usually fall. What drives your bill is your assessed value relative to your neighbors'. If everyone's value climbs by the same proportion, your slice of the total levy holds steady.

What is the difference between assessed value and appraised value?

Appraised value is an estimate of market value from a licensed appraiser following the Uniform Standards of Professional Appraisal Practice (USPAP). Assessed value is a mass-appraisal number the county assessor produces for the whole jurisdiction at once. Different people, different methods, different purposes. They get confused constantly, even by real estate agents.

A lender orders an appraisal before a mortgage closes. That appraisal is an independent, arm's-length opinion of what the property would sell for ^[6]. The appraiser walks the house.

The assessor does not. The assessor's model runs on data for every property in the county, and nobody is visiting your home individually each year. This is why an individual appraisal and the assessor's number can diverge by a wide margin.

Want to challenge your assessed value? A licensed appraisal showing a lower market value is one of the strongest pieces of evidence you can put in front of a review board. Boards and courts treat a USPAP-compliant appraisal as authoritative on market value. The assessed value then follows from applying the legal ratio to that market value.

Appraisals for appeals usually cost $300 to $500 for a house, though pricey markets push that to $700 to $900 ^[6]. Worth it or not depends on the stakes. A $50,000 cut in assessed value in a 2% effective-rate county saves $1,000 a year. The appraisal pays for itself in year one.

How does assessed value affect your property tax bill?

The formula is short: Taxable Value x Tax Rate = Tax Bill. Taxable value is assessed value minus exemptions. The rate comes in mills (thousandths of a dollar per dollar of value) or as a percentage. One mill equals $1 of tax per $1,000 of taxable value.

Run the numbers. Say your assessed value is $280,000 and you claim a $50,000 homestead exemption. Taxable value is $230,000. The mill rate is 22 mills (2.2%). Your bill is $230,000 x 0.022 = $5,060.

Now the assessor bumps your value $40,000 to $320,000. Same exemption, same rate. Taxable value is $270,000. Bill is $270,000 x 0.022 = $5,940. That $40,000 error costs you $880 a year until you fix it.

Most properties get taxed by several overlapping jurisdictions at once: the county, the city or township, the school district, a water district, and so on. Each sets its own rate. The assessor's number feeds all of them. A single assessment error multiplies across every taxing entity that shares the base.

That is why the number matters more than homeowners think. It is more than this year's bill. An inflated assessed value compounds, and in states without automatic caps, it rides along through every reassessment cycle.

How often does assessed value change?

It depends entirely on your state and county. There is no federal rule and no single answer.

Some states reassess every year. Texas requires annual appraisals. California sits at the other end: it only resets assessed value when the property changes hands or you build something new, because Proposition 13 caps annual increases at 2% of the prior year's value ^[7].

Other states run fixed cycles. Illinois reassesses on a triennial (every three years) schedule in most townships, and Cook County does it by thirds each year ^[8]. Pennsylvania assessors can go decades without a countywide reassessment, which builds serious inequity as market values move and assessed values stay frozen.

The reassessment year is usually when your assessed value jumps the most, and it is when most homeowners appeal. Most states give you a short window after the notice lands, typically 30 to 90 days, to file. Miss it and you are stuck with the new value for the whole cycle.

If your county is reassessing and the new number looks too high, move fast. Pull your notice, find the appeal deadline, and stack the assessor's estimate against recent sales of similar homes near you. That comparison is the spine of every winning appeal.

Can assessed value be higher than market value?

Yes. It happens more than people expect, and it is the single most common valid reason to appeal. The legal standard in every state is that assessed value should not exceed what the property would sell for in a fair transaction, adjusted by the applicable ratio.

In a flat or falling market, assessor models built on older sales overshoot. After the 2008 crash, millions of properties carried assessed values above what they could actually sell for. Appeals spiked in 2009 and 2010 in nearly every major county.

Over-assessment also hits individual properties when the wider market is fine. The assessor's file may list the wrong square footage, an extra bathroom that got torn out, or a finished basement that is actually bare studs. Those data errors inflate the number above what an honest appraisal supports.

Winning is usually straightforward. Show the review board three to five recent sales of genuinely comparable homes at prices below your assessed value (adjusted for the ratio) and you can typically get a reduction.

In major metros like Los Angeles, Cook County, Maricopa, and San Diego, the assessor's office publishes recent sales data you can pull to build exactly that case.

What is the assessment ratio and how do you use it?

The assessment ratio is the legally required fraction of market value at which property gets assessed. If your state uses 40% and your home's market value is $350,000, the correct assessed value is $140,000, not $350,000. Knowing the ratio lets you sanity-check the assessor's number in about a minute.

Find it in your state's property tax code or on the state department of revenue site. Then divide your assessed value by the ratio to get the market value the assessor is implying. If that implied value beats what comparable homes are selling for, you have evidence of over-assessment.

Work an example. Assessed value is $168,000, ratio is 40%, so the assessor's implied market value is $420,000. Recent comps are closing at $370,000. The correct assessed value at 40% should be $148,000. That is a $20,000 cut. At a 2% effective rate, you save $400 a year.

Some states set the ratio county by county, because local practice varies. Georgia law fixes it at 40% of fair market value statewide ^[9], so the assessor's value should be 40% of what your home would sell for. Live in Gwinnett, Bibb, or Cherokee County? Run your value against the county's sales data with this exact math. See our guides on Gwinnett County, Bibb County, and Cherokee County for the local specifics.

How do you find your property's assessed value?

Most counties post assessed values in a searchable public database on the assessor's or auditor's website. Enter your address or parcel number and you get the breakdown: land value, improvement value, total assessed value, and often the property characteristics the assessor used. It is public record, so it is free.

You also get a formal assessment notice by mail each year or each cycle. This notice is the official document, and it carries the appeal deadline. In many counties, the notice window is the only time you can challenge the current year's value.

Beyond the county site, county GIS portals and state tax lookup tools publish the same data because it is public. Some states let you download the entire roll in bulk.

To check how your assessment stacks up against local sales, request the comparable sales the assessor used to value your property. In most states, the assessor must hand this over on request or it already sits in the public record. Counties like Bexar County in Texas, Lake County in Illinois, and Madison County each publish this through their own assessor portals.

How do you appeal if your assessed value is wrong?

The appeal has the same shape almost everywhere, even where the names and deadlines differ. Four steps.

Step one: get your notice and note the deadline. Deadlines run from 30 days after the notice date to 90 days or more. Miss it and you almost always wait for the next cycle. Exceptions are rare.

Step two: gather evidence that the value is too high. The strongest evidence is recent sales of comparable properties (comps) near you at prices below what the assessor is using. Backup evidence includes a formal appraisal, photos of condition problems the assessor's file ignores, and outright errors in the property record.

Step three: file with the right body. Depending on your state, that is an informal review with the assessor, a formal hearing with an appraisal review board (Texas calls it the ARB ^[10]), a county assessment appeals board (California), or a board of equalization. Most states offer an informal review first, and it resolves a large share of solid appeals without a hearing.

Step four: present your case. You do not need a lawyer. You need comps, a clear presentation, and the nerve to ask for a specific number. Boards respond better to 'the evidence supports a value of X because these three comps sold for Y, Z, and W' than to a vague complaint that the value feels high.

Want a template and comps worksheet without handing a contingency firm 25 to 40% of your savings? The TaxFightBack DIY Appeal Kit walks each step with county-specific forms and a comps tool. You keep 100% of whatever you win.

Georgia homeowners in Coweta County can check the Coweta County Tax Assessor guide for local deadlines and board procedures.

What is the difference between assessed value and taxable value?

Assessed value is the base before exemptions. Taxable value is what remains after you subtract exemptions from it. The tax rate applies only to taxable value. This distinction is what lets you predict your actual bill.

Exemptions that pull taxable value below assessed value include the homestead exemption (available in most states for owner-occupied primary homes), senior and disability exemptions, veteran exemptions, and agricultural exemptions. The amounts swing wildly. Florida's homestead exemption is $50,000 for most properties ^[11]. Texas added a $100,000 school-tax homestead exemption starting in 2023 ^[10]. Some Georgia counties stack a $2,000 state exemption on top of local ones.

Here is why it matters for appeals. Win a cut in assessed value and the savings flow through before exemptions are figured. Lower assessed value, lower taxable value by the same dollar amount, lower bill. The percentage cut on your bill equals the percentage cut in assessed value, assuming the rate holds.

Deciding whether to bother? Calculate your current taxable value, estimate the reduction your comps support, apply your mill rate, and look at the annual savings. Most property tax pros say appeal if the potential yearly savings clear $200 to $300, because a DIY filing usually costs you only a few hours.

Does a higher assessed value hurt you when you sell?

Not directly. Assessed value does not appear on a sale contract and does not bind a buyer or seller in a negotiation. The only real damage it does is to your annual tax bill, for every year you own the place.

Buyers and agents sometimes glance at assessed value as a rough cross-check on asking price, but the good ones know it can be wildly disconnected from market value, especially in states with rare reassessments or Prop 13-style caps. No lender's appraiser uses assessed value to set a mortgage appraisal.

One indirect wrinkle: in some states, a sale triggers a full reassessment to the sale price. If you have been riding a below-market assessed value (common in California for long-term owners under Prop 13), selling resets the clock for the buyer. The new owner's assessed value gets built on the purchase price. Not your problem as a seller, but worth flagging if you are advising someone who inherited property carrying a very low value and is thinking about selling.

Frequently asked questions

Is assessed value the same as market value?

Not necessarily. In states that assess at 100% of market value, they should sit close. But many states apply an assessment ratio, 10% for Illinois residential property and 40% in Georgia, for example, which makes assessed value a fraction of market value by design. Even in 100% states, mass appraisal models can diverge from actual sale prices by 10 to 20% or more.

Why is my assessed value lower than what I paid for the house?

A few reasons. Your state may use an assessment ratio below 100%, making assessed value a legal fraction of market value. Or you paid above the assessed value because the assessor's model lagged a hot market. In California, if you bought before a recent peak, Proposition 13 caps annual increases at 2%, so assessed value can drift well below current market value over time.

Can I lower my assessed value by filing an appeal?

Yes, and it works more often than most homeowners expect. Studies of large county appeal programs consistently show 40 to 60% of residential appeals get a reduction. You need evidence: recent sales of comparable properties below what your assessed value implies, or documented errors in the assessor's property record. The appeal itself is free in every jurisdiction.

How do I know if my assessed value is too high?

Divide your assessed value by your state's assessment ratio to get the assessor's implied market value. Then search recent sales of similar homes near you, same size, age, and condition, within the last six to twelve months. If those sales come in consistently below the assessor's implied market value, your assessed value is likely too high and worth appealing.

What happens to my assessed value when I do renovations?

Adding square footage, a bedroom, a bathroom, or a finished basement typically triggers a reassessment of the improvement value. The assessor usually learns about big permits through the building department. Cosmetic work generally does not move the assessed value unless it shows up in condition-based adjustments during a reassessment cycle.

Does the assessed value on Zillow or Redfin match my tax bill?

No. Zillow's 'Zestimate' is an automated market value estimate. What Zillow labels 'tax assessed value' comes from public records and reflects the actual county number, but it can lag by six to twelve months. Go straight to your county assessor's website or your official assessment notice for the number that drives your tax bill.

How long does a property tax appeal take?

An informal review with the assessor usually resolves in four to eight weeks. A formal hearing before an appraisal review board or assessment appeals board typically takes two to six months after filing, depending on the county's backlog. In high-volume counties like Cook County in Illinois or Los Angeles County, formal hearings can stretch to six to twelve months.

Do I need a lawyer or property tax consultant to appeal?

No. Most review boards are built to be usable by homeowners without representation. You need good comparable sales data, a clear narrative, and the correct form filed before the deadline. Consultants and attorneys work on contingency, usually 25 to 40% of your first-year savings. On a $1,000 reduction they keep $250 to $400. DIY keeps all of it.

What is the assessment ratio in my state?

It varies. Texas and most New England states assess at or near 100% of market value. Georgia uses 40%. Illinois residential property in Cook County uses 10%. Arizona uses 10% for residential. Confirm with your state's department of revenue or the assessor's office, because some states allow county-level variation from the statewide default.

Does assessed value affect my homeowner's insurance?

No. Homeowner's insurance is based on replacement cost, the cost to rebuild the structure, not its market value or assessed value. A low assessed value does not cut your premium and a high one does not raise it. These are separate calculations that never touch.

What is 'equalized assessed value' or EAV?

Equalized assessed value (EAV) is assessed value adjusted by a state equalization factor to bring every county in a state to a uniform level. Illinois uses this system. The state Department of Revenue publishes an equalization factor for each county each year, and the EAV is the base for school tax levies. In those states, your bill is based on EAV, not raw assessed value.

Can my assessed value go down on its own without an appeal?

It can. If area values fall broadly, mass appraisal models eventually reflect that in reassessment years. But 'eventually' can mean years in counties with rare reassessments. If your market has dropped and your assessed value has not, an appeal is the fastest way to capture the reduction instead of waiting for the next scheduled reassessment.

What if I just bought the house and the assessed value is already above what I paid?

A recent arm's-length sale is usually the strongest evidence of market value there is. In most states, the assessor must give an actual sale price significant weight. File an appeal with your closing disclosure as the main exhibit. Many boards will drop the assessed value to the sale price as a matter of course when the sale is recent and clearly arm's-length.

How does Coweta or Madison County in Georgia handle assessed value disputes?

Both follow Georgia's statewide framework: 40% assessment ratio, formal appeal to the county board of tax assessors within 45 days of the assessment notice, then an optional arbitration or appeal to the Board of Equalization. See our detailed guides on Coweta County and Madison County for specific deadlines and board contact information.

Sources

1. IRS Publication 530, Tax Information for Homeowners: Assessed value is the value placed on property for computing the property tax, distinct from market value.
2. International Association of Assessing Officers (IAAO), Standard on Mass Appraisal of Real Property: IAAO defines assessed value as 'the value placed on property for purposes of computing the property tax' and sets a target median assessment ratio of 90 to 110% with a coefficient of dispersion below 15% for residential properties.
3. National Conference of State Legislatures (NCSL), Property Taxes overview: Most states use mass appraisal to set assessed values annually or on a fixed reassessment cycle.
4. Lincoln Institute of Land Policy, 50-State Property Tax Comparison Study: Assessment ratios and effective tax rates vary widely by state; Illinois Cook County residential ratio is 10%, Georgia is 40%, Texas is near 100%.
5. Lincoln Institute of Land Policy, 50-State Property Tax Comparison Study (2023 edition): Median effective property tax rates and assessment ratios by state compiled from state statutes and assessor data.
6. Appraisal Foundation, Uniform Standards of Professional Appraisal Practice (USPAP): Appraised value is a USPAP-compliant professional estimate of market value; residential appraisals for appeals typically cost $300 to $500.
7. California Board of Equalization, Proposition 13 Overview: Proposition 13 caps California assessed value increases at 2% per year and resets to sale price upon change of ownership.
8. Cook County Assessor's Office, How We Value Property: Cook County reassesses one-third of the county each year on a triennial cycle; residential assessment ratio is 10%.
9. Texas Comptroller of Public Accounts, Property Tax Assistance Division: Texas requires annual appraisals at 100% of market value; homestead exemption for school taxes increased to $100,000 in 2023; appeals are heard by Appraisal Review Boards (ARBs).
10. Florida Department of Revenue, Property Tax Exemptions: Florida's homestead exemption is $50,000 for most owner-occupied residences, reducing taxable value below assessed value.
11. Illinois Department of Revenue, Property Tax Statistics and Equalization: Illinois publishes annual equalization factors by county; equalized assessed value (EAV) is the base used for school and local tax levies.