Key Takeaways
Why the county’s number and the market’s number diverge, and why the gap is widest on land.
- The assessing profession’s own standard permits up to two and a half times more dispersion on vacant land assessments than on newer residential ones.
- South Carolina assesses vacant land at 6 percent of value while an owner-occupied home is assessed at 4 percent, on identical market value.
- Agricultural land is often assessed at a ratio applied to use value rather than market value, which is a discount on top of a discount.
- Louisiana requires statewide reassessment only every four years, so a stale assessment is the rule and not the exception.
- Washington measured more counties failing the dispersion standard on nonresidential property than meeting it.
Assessed value and market value are two different numbers describing the same parcel, and sellers lose money confusing them. The county’s figure exists to calculate property tax. It was never built to tell you what your land will sell for.
That is true of all property. It is worse on land, for reasons that are published and specific, and this covers them: the ratios, the use-value discount, the reassessment lag, and how much error the system formally tolerates before anyone calls it a problem. For the methods that do produce a sale price, the pillar guide starts from the premise that the market does not care what the tax roll says.
This is general information, not tax or legal advice. Assessment ratios, reassessment cycles and appeal procedures are set by state and county, so confirm the specifics with your assessor or a CPA.
Quick verdict: for selling, market value is the only number that matters. The one time the assessment deserves a hard look is when it seems too high, because that is a tax bill you may be able to appeal.
What Is the Difference Between Assessed Value and Market Value?
Purpose. Assessed value is computed by a government to tax a parcel. Market value is what a buyer will pay for it.
IRS Publication 561 gives the standard definition of the second one: fair market value is “the price that property would sell for on the open market. It is the price that would be agreed on between a willing buyer and a willing seller, with neither being required to act, and both having reasonable knowledge of the relevant facts.”
Nothing in that definition involves a county. Assessed value, by contrast, is an input to an arithmetic problem whose output is a tax bill. The two numbers are not competing estimates of the same thing. They are answers to different questions.
The trap is that they describe the same parcel, so sellers assume they should agree, then either panic at a low assessment or defend an asking price with a high one. Both moves cost money.
Why Is the Gap Wider on Land Than on Houses?
Because the system formally tolerates more error on land, and because land gets valued by a different standard in several states.
Start with the tolerance. The International Association of Assessing Officers, the professional body that writes the standards assessors work to, publishes acceptable ranges for the coefficient of dispersion, which measures how far individual assessments scatter around the median ratio. Table 1-3 of its Standard on Ratio Studies:
| Property type | Acceptable COD |
| Single-family residential, newer or homogeneous | 5.0 to 10.0 |
| Single-family residential, older or heterogeneous | 5.0 to 15.0 |
| Vacant land | 5.0 to 25.0 |
Read the bottom row against the top one. The standard permits up to two and a half times more scatter on vacant land, and an assessment sitting 25 percent away from the median ratio is not a failure. It is compliant.
The reason is mundane and worth understanding. Assessors use mass appraisal, valuing thousands of parcels at once from sales data. Houses in a subdivision are near-identical and sell often. Vacant parcels differ in access, zoning, topography, water and shape, and sell rarely. There is simply less to calibrate against, so the profession built a wider band into its own standard.
The standard also caps the overall level of appraisal between 0.90 and 1.10. So even a fully compliant jurisdiction may be assessing at 90 percent or 110 percent of market before any ratio is applied.
What Does That Look Like in Practice?
Washington measured it. The state Department of Revenue’s 2021 ratio report put the statewide median ratio at 0.95, meaning assessed values averaged 95 percent of market value.
Then the dispersion. Residential COD came in at 10.9 percent statewide against the IAAO range of 5 to 15, with 28 counties meeting the standard and 11 exceeding it. Nonresidential COD, the class vacant land sits in, came in at 18.4 percent against a range of 5 to 20, with 19 counties meeting the standard and 20 exceeding it.
More counties failed than passed.
That is one state in one year, and it is not a scandal. It is what mass appraisal of heterogeneous property looks like when someone measures it honestly. But it is the reason a specific parcel’s assessment is a weak guide to that parcel’s price, and it is a far better reason than “assessments are just rough.”
How Do Assessment Ratios Actually Work?
Most states assess at a percentage of value rather than at full value, and the percentage is set in statute or in the constitution.
Two published examples:
Louisiana fixes the ratios constitutionally. Land is assessed at 10 percent of fair market value, improvements for residential purposes at 10 percent, and other property at 15 percent. The state’s own property tax guide confirms the residential figure at 10 percent and commercial at 15 percent.
South Carolina does something sharper. Per the Department of Revenue’s individual property tax guidance, a primary residence with up to five contiguous acres is taxed on an assessment equal to 4 percent, while “second residence or other real property used or held for an individual’s personal use, commercial property, and vacant land is assessed at 6 percent.”
Same market value, same county, same street. The vacant parcel carries a 50 percent higher assessment ratio than the house beside it, purely because nobody lives on it.
This is why an assessed value cannot be compared across state lines, or read as a fraction of market value using any general rule. The fraction is a policy choice, it differs by property class, and on land it is frequently the less favourable class.
Why Do Agricultural Parcels Look So Strange?
Because the ratio is applied to use value, not market value. It is a discount on a discount.
South Carolina assesses agricultural real property at 4 percent for individuals and partnerships, or 6 percent for most corporations, of its value for agricultural use purposes. Louisiana assesses agricultural, horticultural, marsh and timber lands at 15 percent of use value.
Use value is what the ground is worth farming, not what it is worth to a buyer. On a parcel in a growth path, the two can diverge enormously, and the assessment will reflect the farm and ignore the market entirely.
If your parcel carries an agricultural, timber or greenbelt classification, its assessed value is not a low estimate of market value. It is a correct calculation of something else. Treating it as a price signal is the most expensive version of this mistake, and it is concentrated in exactly the rural parcels where sellers are least likely to have comparable sales at hand.
Worth knowing before you sell: removing a use-value classification can trigger rollback tax in many states. Check before you change anything.
How Stale Can an Assessment Be?
In Louisiana, legally up to four years, and often more in practice.
The state’s guidance is explicit: “While a statewide reassessment is required at least every four years, a property may be reassessed at any time.” Four years is the floor on the cycle, not the ceiling on the lag. A parcel reassessed in year one of a cycle and sold in year four is carrying a number set against a market that has since moved.
Stack the three effects and the size of the gap stops being mysterious. A ratio set by policy, applied to a value that may sit anywhere between 90 and 110 percent of market, produced by a process formally allowed to scatter 25 percent on land, from data that may be four years old.
None of that is a flaw in the assessment. It is a tax instrument performing correctly. It is just not a price.
What Should You Price On Instead?
Sold comparables, adjusted. That is the method, and it is the same one the IRS names.
Publication 561 lists comparable sales first among the approaches for valuing real property, adjusting the selling prices of similar properties for differences in date, size, condition and location. Capitalisation of income and replacement cost sit behind it, and replacement cost tends to set an upper limit rather than a value.
For land the adjustments are where the work is. Quality of comps matters far more than the number of them, and a nearby parcel with paved access is not a comparable for a landlocked one at any acreage.
Rank the three numbers by relevance and the confusion resolves. Market value sets your asking price. An appraisal confirms it when real money turns on the answer, because an appraiser inspects the specific parcel rather than modelling thousands at once. Assessed value tells you your tax bill and nothing else.
What Do Sellers Get Wrong?
Four mistakes, the first of which costs the most.
Listing at or near the assessment. In a 6 percent ratio state that is not a discount, it is a giveaway of most of the value. Buyers who know the ratio will take that price immediately.
Treating a high assessment as a price floor. It is not evidence of market value and buyers will not treat it as such. Overpricing on that basis is how a parcel sits for a year before the seller has to make one meaningful cut rather than the series of small ones that signal a motivated seller.
Accepting a lowball justified by the assessment. A buyer pointing at your tax card is making a rhetorical argument, not a valuation one. The counter is sold comparables, and it works because it is the actual standard.
Ignoring a high assessment. If the number looks above what the parcel would fetch, that is a live tax overpayment, not a bragging right. Most counties have a formal appeal window that opens once a year and closes quickly.
Should You Appeal Your Assessment?
If the assessed value implies a market value above what the parcel would actually sell for, yes, and the evidence is the same evidence you would use to price it.
Work out what the ratio in your state is, divide the assessed value by it, and compare the implied market value to recent sales of genuinely similar parcels. If the implied figure is high, you have an appeal. If it is low, you have a low tax bill and no complaint worth making.
Two cautions. Appeal deadlines are short and jurisdiction-specific, and an appeal puts your parcel in front of the assessor, which occasionally works out the other way. If you are unsure what your state’s ratio or window is, your assessor’s office will tell you, or you can send an email and we will point you to the right office.
How Should You Set the Price?
On sold comparables, with the tax card left out of the calculation entirely.
Pull recent sales of parcels genuinely like yours, adjust honestly for access, zoning, topography and size, and reconcile to a figure you can defend with evidence. Where the stakes justify it, an appraisal confirms the number. Where they do not, good comparables are enough.
You can see what comparable parcels are actually asking by price per acre and acreage, which is the closest live read on demand available without pulling records.
When your number is set, put the parcel in front of buyers at a price built on the market rather than on the tax roll.
Frequently Asked Questions
Is assessed value the same as market value?
No. Assessed value is computed by a county to calculate property tax, usually by applying a statutory ratio to an estimated value. Market value is what a willing buyer would pay a willing seller. Ratios are set by state policy and differ by property class, so the two numbers rarely match and cannot be compared across jurisdictions.
Why is my land’s assessed value so much lower than market value?
Usually the assessment ratio. South Carolina assesses vacant land at 6 percent of value; Louisiana assesses land at 10 percent. Agricultural classifications go further and apply the ratio to agricultural use value rather than market value. Add a reassessment cycle that can run four years and the gap widens further.
Are land assessments less accurate than home assessments?
By the profession’s own standard, they are permitted to be. IAAO’s Standard on Ratio Studies allows a coefficient of dispersion of 5.0 to 25.0 on vacant land against 5.0 to 10.0 on newer single-family residential. Vacant parcels vary more and sell less often, so mass appraisal has less to calibrate against.
Can assessed value be higher than market value?
Yes. A market that has declined since the last reassessment, or an over-valued parcel, can leave the assessment above what the land would sell for. That is a tax overpayment and most counties have a formal appeal process. Deadlines are short and set locally, so check your assessor’s calendar.
What is the difference between appraised value and assessed value?
An appraisal is a licensed appraiser’s opinion of a specific parcel’s value, based on inspection and comparable sales, and it lands near market value. Assessed value is produced by mass appraisal for taxation and is usually a ratio of an estimated value. Appraisals are used for loans and disputes; assessments are used only for tax.
Resources and Further Reading
What Is the Difference Between Assessed Value and Market Value?
Purpose. Assessed value is computed by a government to tax a parcel. Market value is what a buyer will pay for it.
IRS Publication 561 gives the standard definition of the second one: fair market value is “the price that property would sell for on the open market. It is the price that would be agreed on between a willing buyer and a willing seller, with neither being required to act, and both having reasonable knowledge of the relevant facts.”
Nothing in that definition involves a county. Assessed value, by contrast, is an input to an arithmetic problem whose output is a tax bill. The two numbers are not competing estimates of the same thing. They are answers to different questions.
The trap is that they describe the same parcel, so sellers assume they should agree, then either panic at a low assessment or defend an asking price with a high one. Both moves cost money.
Why Is the Gap Wider on Land Than on Houses?
Because the system formally tolerates more error on land, and because land gets valued by a different standard in several states.
Start with the tolerance. The International Association of Assessing Officers, the professional body that writes the standards assessors work to, publishes acceptable ranges for the coefficient of dispersion, which measures how far individual assessments scatter around the median ratio. Table 1-3 of its Standard on Ratio Studies:
| Property type | Acceptable COD |
| Single-family residential, newer or homogeneous | 5.0 to 10.0 |
| Single-family residential, older or heterogeneous | 5.0 to 15.0 |
| Vacant land | 5.0 to 25.0 |
Read the bottom row against the top one. The standard permits up to two and a half times more scatter on vacant land, and an assessment sitting 25 percent away from the median ratio is not a failure. It is compliant.
The reason is mundane and worth understanding. Assessors use mass appraisal, valuing thousands of parcels at once from sales data. Houses in a subdivision are near-identical and sell often. Vacant parcels differ in access, zoning, topography, water and shape, and sell rarely. There is simply less to calibrate against, so the profession built a wider band into its own standard.
The standard also caps the overall level of appraisal between 0.90 and 1.10. So even a fully compliant jurisdiction may be assessing at 90 percent or 110 percent of market before any ratio is applied.
What Does That Look Like in Practice?
Washington measured it. The state Department of Revenue’s 2021 ratio report put the statewide median ratio at 0.95, meaning assessed values averaged 95 percent of market value.
Then the dispersion. Residential COD came in at 10.9 percent statewide against the IAAO range of 5 to 15, with 28 counties meeting the standard and 11 exceeding it. Nonresidential COD, the class vacant land sits in, came in at 18.4 percent against a range of 5 to 20, with 19 counties meeting the standard and 20 exceeding it.
More counties failed than passed.
That is one state in one year, and it is not a scandal. It is what mass appraisal of heterogeneous property looks like when someone measures it honestly. But it is the reason a specific parcel’s assessment is a weak guide to that parcel’s price, and it is a far better reason than “assessments are just rough.”
How Do Assessment Ratios Actually Work?
Most states assess at a percentage of value rather than at full value, and the percentage is set in statute or in the constitution.
Two published examples:
Louisiana fixes the ratios constitutionally. Land is assessed at 10 percent of fair market value, improvements for residential purposes at 10 percent, and other property at 15 percent. The state’s own property tax guide confirms the residential figure at 10 percent and commercial at 15 percent.
South Carolina does something sharper. Per the Department of Revenue’s individual property tax guidance, a primary residence with up to five contiguous acres is taxed on an assessment equal to 4 percent, while “second residence or other real property used or held for an individual’s personal use, commercial property, and vacant land is assessed at 6 percent.”
Same market value, same county, same street. The vacant parcel carries a 50 percent higher assessment ratio than the house beside it, purely because nobody lives on it.
This is why an assessed value cannot be compared across state lines, or read as a fraction of market value using any general rule. The fraction is a policy choice, it differs by property class, and on land it is frequently the less favourable class.
Why Do Agricultural Parcels Look So Strange?
Because the ratio is applied to use value, not market value. It is a discount on a discount.
South Carolina assesses agricultural real property at 4 percent for individuals and partnerships, or 6 percent for most corporations, of its value for agricultural use purposes. Louisiana assesses agricultural, horticultural, marsh and timber lands at 15 percent of use value.
Use value is what the ground is worth farming, not what it is worth to a buyer. On a parcel in a growth path, the two can diverge enormously, and the assessment will reflect the farm and ignore the market entirely.
If your parcel carries an agricultural, timber or greenbelt classification, its assessed value is not a low estimate of market value. It is a correct calculation of something else. Treating it as a price signal is the most expensive version of this mistake, and it is concentrated in exactly the rural parcels where sellers are least likely to have comparable sales at hand.
Worth knowing before you sell: removing a use-value classification can trigger rollback tax in many states. Check before you change anything.
How Stale Can an Assessment Be?
In Louisiana, legally up to four years, and often more in practice.
The state’s guidance is explicit: “While a statewide reassessment is required at least every four years, a property may be reassessed at any time.” Four years is the floor on the cycle, not the ceiling on the lag. A parcel reassessed in year one of a cycle and sold in year four is carrying a number set against a market that has since moved.
Stack the three effects and the size of the gap stops being mysterious. A ratio set by policy, applied to a value that may sit anywhere between 90 and 110 percent of market, produced by a process formally allowed to scatter 25 percent on land, from data that may be four years old.
None of that is a flaw in the assessment. It is a tax instrument performing correctly. It is just not a price.
What Should You Price On Instead?
Sold comparables, adjusted. That is the method, and it is the same one the IRS names.
Publication 561 lists comparable sales first among the approaches for valuing real property, adjusting the selling prices of similar properties for differences in date, size, condition and location. Capitalisation of income and replacement cost sit behind it, and replacement cost tends to set an upper limit rather than a value.
For land the adjustments are where the work is. Quality of comps matters far more than the number of them, and a nearby parcel with paved access is not a comparable for a landlocked one at any acreage.
Rank the three numbers by relevance and the confusion resolves. Market value sets your asking price. An appraisal confirms it when real money turns on the answer, because an appraiser inspects the specific parcel rather than modelling thousands at once. Assessed value tells you your tax bill and nothing else.
What Do Sellers Get Wrong?
Four mistakes, the first of which costs the most.
Listing at or near the assessment. In a 6 percent ratio state that is not a discount, it is a giveaway of most of the value. Buyers who know the ratio will take that price immediately.
Treating a high assessment as a price floor. It is not evidence of market value and buyers will not treat it as such. Overpricing on that basis is how a parcel sits for a year before the seller has to make one meaningful cut rather than the series of small ones that signal a motivated seller.
Accepting a lowball justified by the assessment. A buyer pointing at your tax card is making a rhetorical argument, not a valuation one. The counter is sold comparables, and it works because it is the actual standard.
Ignoring a high assessment. If the number looks above what the parcel would fetch, that is a live tax overpayment, not a bragging right. Most counties have a formal appeal window that opens once a year and closes quickly.
Should You Appeal Your Assessment?
If the assessed value implies a market value above what the parcel would actually sell for, yes, and the evidence is the same evidence you would use to price it.
Work out what the ratio in your state is, divide the assessed value by it, and compare the implied market value to recent sales of genuinely similar parcels. If the implied figure is high, you have an appeal. If it is low, you have a low tax bill and no complaint worth making.
Two cautions. Appeal deadlines are short and jurisdiction-specific, and an appeal puts your parcel in front of the assessor, which occasionally works out the other way. If you are unsure what your state’s ratio or window is, your assessor’s office will tell you, or you can send an email and we will point you to the right office.
How Should You Set the Price?
On sold comparables, with the tax card left out of the calculation entirely.
Pull recent sales of parcels genuinely like yours, adjust honestly for access, zoning, topography and size, and reconcile to a figure you can defend with evidence. Where the stakes justify it, an appraisal confirms the number. Where they do not, good comparables are enough.
You can see what comparable parcels are actually asking by price per acre and acreage, which is the closest live read on demand available without pulling records.
When your number is set, put the parcel in front of buyers at a price built on the market rather than on the tax roll.
Frequently Asked Questions
Is assessed value the same as market value?
No. Assessed value is computed by a county to calculate property tax, usually by applying a statutory ratio to an estimated value. Market value is what a willing buyer would pay a willing seller. Ratios are set by state policy and differ by property class, so the two numbers rarely match and cannot be compared across jurisdictions.
Why is my land’s assessed value so much lower than market value?
Usually the assessment ratio. South Carolina assesses vacant land at 6 percent of value; Louisiana assesses land at 10 percent. Agricultural classifications go further and apply the ratio to agricultural use value rather than market value. Add a reassessment cycle that can run four years and the gap widens further.
Are land assessments less accurate than home assessments?
By the profession’s own standard, they are permitted to be. IAAO’s Standard on Ratio Studies allows a coefficient of dispersion of 5.0 to 25.0 on vacant land against 5.0 to 10.0 on newer single-family residential. Vacant parcels vary more and sell less often, so mass appraisal has less to calibrate against.
Can assessed value be higher than market value?
Yes. A market that has declined since the last reassessment, or an over-valued parcel, can leave the assessment above what the land would sell for. That is a tax overpayment and most counties have a formal appeal process. Deadlines are short and set locally, so check your assessor’s calendar.
What is the difference between appraised value and assessed value?
An appraisal is a licensed appraiser’s opinion of a specific parcel’s value, based on inspection and comparable sales, and it lands near market value. Assessed value is produced by mass appraisal for taxation and is usually a ratio of an estimated value. Appraisals are used for loans and disputes; assessments are used only for tax.
