Assessed value definition: what it means for your property tax bill

Last updated 2026-07-09

What is assessed value, exactly?

Assessed value is the number your county or local assessor puts on your property for tax purposes. Your tax bill is that number multiplied by your local tax rate (the mill levy or millage rate), minus any exemptions you qualify for. That's the whole formula.

Simple on paper. The confusion starts immediately, because assessed value and market value are not the same thing in most states. Market value is what a buyer would pay for your home today on the open market. Assessed value is what the assessor says it's worth for tax purposes, and that figure is often a fraction of market value.

That fraction is called the assessment ratio (sometimes the assessment level or equalization factor), and it swings hard by state and county. California's Proposition 13 limits assessed value increases to 2% per year regardless of what the market does, so a house bought decades ago can carry an assessed value far below its sale price ^[1]. In Texas, assessed value is supposed to equal 100% of market value, but state law caps how much it can rise each year on homesteaded properties ^[2]. In Cook County, Illinois, residential properties are assessed at 10% of market value by statute ^[3].

The practical result: in some places your assessed value tracks market value closely, in others it barely relates. Learn your state's rules before you judge whether your assessment is fair.

How is assessed value different from market value and appraised value?

Assessed value is the assessor's tax figure, market value is what a buyer would pay, and appraised value is a licensed appraiser's opinion for your lender. Homeowners and even some real estate agents use these three terms interchangeably. They are three different numbers set by three different people under three different rules.

Market value is what your home would sell for between a willing buyer and a willing seller, neither under pressure. It's an estimate, not a fact, but it's grounded in actual comparable sales.

Appraised value usually means a licensed appraiser's opinion of market value, typically done for mortgage purposes. A bank appraisal and a tax assessment are separate animals.

Assessed value is the assessor's figure used only for tax calculation. In states with a fractional assessment ratio, the assessor might start with an estimate of market value and apply the ratio. In others, the assessor tries to set assessed value equal to market value directly.

Term	Who produces it	Primary use	Legally required to equal market value?
Market value	No single party; derived from sales	Real estate transactions, lending	N/A
Appraised value	Licensed appraiser	Mortgage underwriting	No, but should track it
Assessed value	County/local assessor	Property tax calculation	Depends on state law
Taxable value	Assessor, after exemptions	Final tax bill calculation	No

Look at the fourth row. Taxable value is assessed value after you subtract exemptions like a homestead exemption, senior freeze, or disability exemption. Your actual tax bill runs off taxable value, not raw assessed value. Both numbers show up on your assessment notice, and both matter.

What is the assessment ratio and why does it matter?

The assessment ratio is the legally mandated relationship between assessed value and market value in your jurisdiction. A ratio of 100% means the assessor is supposed to value your home at full market value. A ratio of 25% means the assessed value should be one-quarter of market value.

This is the part that trips up first-time appeals. If your state has a ratio below 100%, you can't just argue the assessor valued your home higher than it would sell for. You have to compare apples to apples. If the ratio is 25% and your home would sell for $400,000, a correct assessed value is $100,000. If the assessor put $130,000, that gap is your case, and $130,000 is the number you fight.

Some states add an equalization factor, a multiplier applied to every property in a county to pull the average assessed value up to state-mandated levels. Cook County, Illinois uses this system ^[3]. When the equalization factor is 2.916, as it has been in Cook County in recent years, the assessor's base value gets multiplied by that number before the tax rate hits. This matters if you're comparing your bill to a neighbor's in a different county.

You can usually find your state's statutory assessment ratio in your state's property tax code or on your state department of revenue's website. The Lincoln Institute of Land Policy tracks these ratios across all 50 states and publishes them every year ^[4].

How do assessors actually calculate assessed value?

Most residential assessors lean on one of three approaches, or some blend of them. The sales comparison approach handles most single-family homes, the cost approach handles new or unusual buildings, and the income approach handles rentals.

The sales comparison approach is the workhorse for single-family homes. The assessor looks at recent sales of comparable homes in your area and adjusts for differences like square footage, age, condition, and lot size. It's basically what a mortgage appraiser does, but run at mass scale across thousands of properties with statistical models instead of individual inspections.

The cost approach estimates what it would cost to rebuild your home from scratch (replacement cost), subtracts depreciation for age and condition, then adds land value. Assessors reach for it on newer properties and special-use buildings where comparable sales are thin.

The income approach applies to rental and commercial property. The assessor estimates the income the property could generate, applies a capitalization rate, and works backward to a value. If you own a home you live in, this probably doesn't touch you. If you rent out your place or own a small investment property, you may see it ^[5].

Mass appraisal introduces error. Your assessor is not walking through your home every cycle. The models run on data, and the data has mistakes: wrong square footage, a bathroom count that never got updated, a finished basement the records call unfinished. These errors are common and worth checking before you assume the valuation method itself is broken.

How do you find your property's assessed value?

Go to your county assessor's website, enter your address or parcel ID number, and your current assessed value shows on screen. Most counties post assessed values in a searchable database. If you don't know your parcel ID, it's printed on your property tax bill.

No online search tool? That's rarer now but still real in some rural counties. Call the assessor's office or visit in person. You have a legal right to see the assessment record for your own property in every state.

Your annual assessment notice, mailed once a year (timing varies, often in spring), also lists your assessed value, the prior year's value, and usually a deadline to appeal. Keep that notice. The appeal deadline printed on it is almost always a hard cutoff, and missing it by one day generally means waiting a full year.

For how this plays out in specific big counties, see Los Angeles County property tax, Maricopa property tax, and San Diego property tax.

Why is my assessed value higher than what my home would actually sell for?

It happens, and it usually comes down to one of three things: a stale reassessment cycle, a data error on your property card, or a mass appraisal model that weights your neighborhood wrong. Any of the three gives you grounds to appeal.

Market values can fall faster than assessment cycles run. If your county reassesses every three years and prices dropped 15% last year, your assessed value might still be built on peak numbers. You're being taxed on a value that no longer exists.

Data errors do it too. Your property card might show 2,400 square feet when you have 2,100. It might list four bedrooms when you have three. It might show a renovated kitchen that never got renovated.

Sometimes the mass appraisal model simply weights certain neighborhoods or property types wrong. A 2017 ProPublica and Chicago Tribune investigation found systematic overassessment of lower-value homes in Cook County relative to higher-value homes, a pattern also documented in academic research on regressive assessments ^[6]. This is not a Cook County problem alone. Studies in other states have found the same tilt.

If your assessed value is above market value in a 100%-ratio state, or above the required ratio times market value in a fractional-ratio state, you can appeal. The process is more open to regular homeowners than most people think, and you don't need to hand a contingency firm 30% to 50% of your first year's savings to use it.

What is the relationship between assessed value and property tax rates?

Your tax bill is taxable value (assessed value minus exemptions) multiplied by the total millage rate for your jurisdiction. Reduce the assessed value and you cut the bill across every layer of that millage rate at once.

A mill is one-tenth of one cent, or $1 per $1,000 of taxable value. If your taxable value is $250,000 and your total millage rate is 20 mills (0.02), your annual property tax bill is $5,000.

Millage rates stack in layers: city or county government, school district, fire district, community college, sometimes other special districts. Each entity sets its own rate. The sum is what hits your bill. You generally can't appeal the millage rate (budgets and elections set that), but you can appeal the assessed value.

Cutting assessed value has a multiplier effect. Every $10,000 reduction in assessed value saves you $10,000 times your total millage rate. At 20 mills, a $50,000 reduction saves $1,000 a year, and that saving compounds, because your new lower value becomes the base for future assessments.

Georgia homeowners run this math against a fixed ratio. Gwinnett County tax assessor, Cherokee County tax assessor, and Coweta County tax assessor all follow Georgia's 40% assessment ratio under O.C.G.A. § 48-5-7, meaning assessed value is set at 40% of fair market value ^[7].

How often does assessed value change?

Reassessment schedules vary by state and county. Some reassess annually. Others do it every two, three, or four years. A few states reassess only when a property sells.

California is the famous example of sale-triggered reassessment under Proposition 13, which limits reassessment to the point of sale, with that 2% annual cap between sales ^[1]. Texas counties reassess annually, though the homestead cap limits how much the taxable value can rise each year ^[2].

State	Reassessment frequency	Assessment ratio	Notes
California	On sale + 2%/yr cap	100% of base year value	Prop. 13 controls
Texas	Annual	100% market value	Homestead cap 10%/yr
Illinois (Cook County)	Triennial	10% residential	Equalization factor applied
Georgia	Annual	40% fair market value	O.C.G.A. § 48-5-7
New York	Varies by municipality	Varies	Set locally
Florida	Annual	100% but Save Our Homes caps increases at 3%/yr or CPI

When a reassessment cycle lands, your assessed value can jump hard if market values climbed since the last cycle. That's when appeal activity spikes. You typically get 30 to 90 days from the date your notice is mailed to file a formal appeal, depending on your jurisdiction. Missing that window is the most common reason appeals fail ^[8].

Can you lower your assessed value, and how do you start?

Yes, and appeals win at real rates. Success rates vary by county, but many boards of equalization and assessment review boards report that 30% to 60% of residential appeals get a reduction. Nobody has clean national data on this. County-level reports from Cook County, Bexar County, and Maricopa County all show meaningful reduction rates for appeals filed on time.

Start by checking your property record for errors. Pull up your parcel on the assessor's website and match every data point to reality: square footage, lot size, bedroom count, bath count, garage, finished basement, pool, year built. Factual errors are the easiest wins, because they need no valuation argument at all.

Next, gather comparable sales. Find three to five homes near you that sold in the six to twelve months before your assessment date, similar in size, age, and condition, and sold for less than what your assessed value implies. The assessor's website often shows recent sales. Zillow, Redfin, and county recorder deed records help too.

Then file before the deadline. The form is usually one or two pages on the assessor's website. Most counties take it by mail, online, or in person.

Want a structured walkthrough for building and presenting the evidence yourself? The TaxFightBack DIY appeal kit has the forms, comparable-sale worksheets, and county checklists to run the whole process without paying a contingency fee.

For local filing details, Bexar County tax assessor, Cook County tax assessor tax bill, Madison County tax assessor, and Bibb County tax assessor pages carry deadlines and procedures.

What exemptions can reduce your taxable value after assessed value is set?

Even a perfectly accurate assessed value can leave you overpaying if you're missing exemptions. Exemptions cut your taxable value after the assessed value is set, so they reduce the bill without touching the underlying valuation.

The homestead exemption is the most widely available. Most states offer it to owner-occupants on their primary residence. Amounts range from a flat $500 in some states to $50,000 or more in others. Florida's homestead exemption is $25,000 on assessed value, plus another $25,000 on assessed value above $50,000 (excluding school taxes), for a potential $50,000 cut in taxable value ^[9].

Senior exemptions are common and often stack on top of the homestead exemption. Some states offer a senior freeze that caps taxable value once you turn 65 and meet income thresholds.

Veteran and disability exemptions exist in most states and can be large. Texas gives a $12,000 exemption to certain disabled veterans and a full property tax exemption to veterans with a 100% disability rating from the VA ^[2].

You have to apply. These are not automatic in most jurisdictions. If you've never filed for your homestead exemption, you may have overpaid for years, and some counties allow retroactive claims two to five years back.

Missouri residents dealing with a related but separate tax should read St. Louis County personal property tax, which covers that category and its exemptions.

How does assessed value affect homes that were recently purchased?

In most states, buying a home triggers a reassessment to the purchase price, or at least a review. Pay $550,000 for a house the county's model had at $480,000, and expect the assessed value to jump once the sale processes.

California works differently under Proposition 13. The sale price becomes the new base year value, and future increases cap at 2% per year until the next sale ^[1]. That's why long-time California owners can carry assessed values that are a fraction of what identical homes next door just sold for.

In states without that cap, like Texas, your purchase price is direct evidence of market value, and the assessor will use it. If you overpaid in a bidding war and the market has since cooled, your assessed value might now sit above what you could actually sell for. That's an appeal.

One practical point. If you bought recently and believe you paid above true market value, gather data on what comparable homes sold for after your purchase. A single sale, your own, is relevant but not conclusive. Several lower post-purchase comparables make a much stronger case.

What does assessed value look like across major U.S. counties?

The spread between counties and states is wide. The figures below use the Lincoln Institute's 50-State Property Tax Comparison Study ^[4] and show the effective tax rate on market value, which folds the assessment ratio and the millage rate together. These are real numbers from their published data.

New Jersey consistently ranks as the highest effective property tax state. Illinois, Texas, and New Hampshire sit in the top tier. Alabama, Hawaii, and Colorado stay among the lowest.

For a homeowner, the takeaway is blunt: the same $400,000 home produces radically different bills depending on where it sits. A $400,000 home in Trenton, New Jersey can run over $10,000 a year in property taxes. The same home in Honolulu might run under $2,000. Tax rates drive part of that gap, assessment levels and ratios drive the rest, which is why you need to know your local framework before deciding whether to appeal.

Lake County, Illinois carries some of the highest effective property tax rates in the country. Lake County property tax breaks down that county's assessment and appeal process.

Frequently asked questions

Is assessed value the same as market value?

No. Market value is what your home would sell for on the open market. Assessed value is what the county uses for tax purposes. In states with fractional assessment ratios, assessed value is intentionally set below market value, sometimes as low as 10% of it. Even in 100%-ratio states, the two figures can diverge because assessors use statistical models, not individual sales, to set values.

What does tax assessed value definition mean legally?

The legal definition varies by state statute. Most state property tax codes define it as the assessor's estimate of a property's market value (or a specified fraction of it) as of a particular assessment date. Georgia law under O.C.G.A. § 48-5-7 sets residential assessed value at 40% of fair market value. Your state's department of revenue or revenue code holds the controlling definition for your property.

Can my assessed value be higher than what I paid for my home?

Yes, and it happens. If the market rose sharply after your purchase and the county reassessed, your current assessed value can exceed your original purchase price. It can also exceed current market value if prices have since dropped. Both situations are valid grounds for an appeal, though you'll need comparable sales data, more than your purchase contract, to make the case stick.

How do I find out my home's assessed value?

Go to your county assessor's website and search by address or parcel number. The current assessed value, prior year value, and the property data the assessor is using (square footage, bedroom count, and so on) all appear. If your county has no online portal, your annual assessment notice states the value, or you can call the assessor's office directly. The information is public record.

What is the assessment ratio and how do I find mine?

The assessment ratio is the legally required percentage of market value at which property is assessed. A ratio of 100% means assessed value equals market value. A ratio of 25% means it should equal one-quarter. Find your state's ratio in your state property tax statute or on your state department of revenue's website. The Lincoln Institute of Land Policy also publishes a 50-state comparison of assessment ratios each year.

How much can assessed value increase each year?

It depends entirely on your state. California caps increases at 2% per year between sales under Proposition 13. Texas caps the increase in taxable value for homesteaded properties at 10% per year. Florida's Save Our Homes provision limits increases to 3% or the CPI, whichever is lower. Many states have no cap at all for non-homesteaded properties. Check your state's property tax code or department of revenue for the specific rule.

What happens if I disagree with my assessed value?

You file a formal appeal with your local board of equalization, assessment appeals board, or the equivalent body in your state. It starts with a simple form submitted before the deadline printed on your assessment notice, typically 30 to 90 days from the notice date. You present evidence, usually comparable sales or a documented property data error, at an informal or formal hearing. No attorney is required.

Do I need to hire a tax attorney or contingency firm to appeal?

No. Residential property tax appeals are built for homeowners without legal representation. The hearing is informal in most counties, the forms are short, and the evidence required (comparable sales, property record corrections) is something you can gather yourself. Contingency firms typically charge 25% to 50% of your first year's tax savings. If your appeal wins, that comes straight out of money you'd otherwise keep.

Does appealing my assessed value affect my neighbors' taxes?

No. Your appeal applies only to your parcel. Winning a reduction does not raise anyone else's assessment or change the millage rate directly. The revenue loss to the taxing district from a single residential appeal is too small to move rates. Commercial owners sometimes worry about this in aggregate, but for a standard homeowner appeal, there's no mechanism by which your reduction hurts your neighbors.

How far back can I appeal a property tax assessment?

You can only appeal the current assessment year's value within the deadline window stated on your notice. You generally cannot reach back and appeal prior years after their deadlines pass, with narrow exceptions in some states for clerical errors. Missing the deadline printed on your notice is the most common and most costly mistake homeowners make. File on time, even if your case isn't fully built yet.

What is the difference between assessed value and taxable value?

Assessed value is the base figure the assessor sets. Taxable value is what remains after you subtract any exemptions you qualify for, like a homestead, senior, or veteran exemption. Your actual tax bill is calculated on taxable value, not assessed value. Both numbers appear on your assessment notice and your tax bill. With a homestead exemption in place, your taxable value should sit noticeably below your assessed value.

My assessed value went up but my neighbor's didn't. Is that fair?

It might not be, and it's worth investigating. Uniform and equal treatment is a core principle of property taxation in most states. If similar properties in your area are assessed differently, that inconsistency is itself grounds for appeal in many jurisdictions, separate from whether your value is above market. Pull your neighbors' assessed values from public records and compare. A pattern of unequal treatment strengthens your case.

What is an equalization factor and does it affect my assessed value?

An equalization factor (also called a multiplier) is applied by some states to pull assessed values across counties into alignment with a state-mandated level. Cook County, Illinois applies a factor set by the Illinois Department of Revenue each year. If your county's factor is greater than 1.0, it multiplies your assessor's value upward before your tax rate applies. Your county assessor's website or state department of revenue shows the current factor.

Does a higher assessed value mean I should sell my house?

Not necessarily. Assessed value and sale value are related but not equal, especially in states with assessment caps or fractional ratios. A higher assessed value does mean a higher tax bill, which is a real cost. It's also a signal to check whether the assessor's market value estimate is accurate. If the assessed value reflects genuine appreciation in your home's worth, that's good for you economically even when the tax increase stings.

Sources

1. California State Board of Equalization, Proposition 13 Overview: California's Proposition 13 limits annual increases in assessed value to 2% and triggers reassessment at the point of sale to the purchase price as the new base year value.
2. Texas Comptroller of Public Accounts, Property Tax Exemptions: Texas assesses property at 100% of market value, caps homestead taxable value increases at 10% per year, and provides a full property tax exemption for 100% VA-rated disabled veterans.
3. Cook County Assessor's Office, How Property Is Assessed: Cook County, Illinois assesses residential properties at 10% of market value by statute, with an equalization factor applied by the Illinois Department of Revenue.
4. Lincoln Institute of Land Policy, 50-State Property Tax Comparison Study: The Lincoln Institute publishes annual 50-state comparisons of effective property tax rates and assessment ratios across U.S. jurisdictions.
5. International Association of Assessing Officers (IAAO), Standard on Mass Appraisal: The IAAO identifies three standard approaches to value used in mass appraisal: sales comparison, cost, and income approaches.
6. ProPublica / Chicago Tribune, The Tax Divide investigation (2017): A joint investigation found systematic overassessment of lower-value properties relative to higher-value properties in Cook County, consistent with academic research documenting regressive assessment patterns.
7. Georgia General Assembly, O.C.G.A. § 48-5-7: Georgia law sets residential property assessed value at 40% of fair market value.
8. National Taxpayers Union Foundation, Property Tax Appeal Guide: Appeal deadlines in most jurisdictions run 30 to 90 days from the mailing date of the assessment notice; missing the deadline forfeits the right to appeal for that assessment year.
9. Florida Department of Revenue, Property Tax Exemptions: Florida's homestead exemption provides up to $50,000 in assessed value reduction for owner-occupied primary residences, applied in two $25,000 tiers.
10. Illinois Department of Revenue, Property Tax System Overview: Illinois applies county-level equalization factors (multipliers) to bring assessed values into conformance with the state's mandated 33.33% assessment level for most property classes.
11. New York State Department of Taxation and Finance, Understanding the Property Tax: New York assessment ratios and reassessment schedules vary by municipality and are set locally, resulting in wide variation within the state.