Quick answer: Property tax is usually based on assessed value, not the price you paid. Your county multiplies the assessed value by the total mill levy and divides by 1,000, then applies any credits. An appeal changes the assessed value, so that is the number to challenge, before the county deadline.
The formula
Douglas County, Kansas, publishes its residential method in steps. First, appraised value times 11.5% gives the assessed value. Then assessed value times the total mill levy, divided by 1,000, gives the tax. The county then subtracts a $46 residential credit. One mill is one dollar of tax for every $1,000 of assessed value. Other counties use different rates, credits and structures, so check your own notice.
Worked example (made-up numbers, simplified)
This example leaves out the assessment rate and the credit, so the arithmetic is easy to follow. An assessed value of $200,000 and a total of 25 mills gives a yearly tax of $5,000. A new assessment of $230,000 raises that to $5,750, which is $750 a year or about $62.50 a month. If an appeal lowers the assessment by $20,000, the yearly saving is $500.
At 25 mills, each $10,000 of assessed value costs $250 a year. Each single mill on $200,000 is $200 a year, so a small change in the rate matters too.
Assessed value is not market value
Many counties assess at a set percentage of market value. Douglas County's published residential rate is 11.5% of appraised value. The figure on your notice is the one that is taxed, so an appeal targets that figure, not the price you paid or an estimate on a website.
Questions people ask
How much is one mill?
One mill is one dollar of tax for every $1,000 of assessed value. At 25 mills, that is $25 per $1,000, or $25,000 of tax on $1,000,000 of assessed value.
Does buying a house at a higher price raise my property tax?
Not directly. Tax follows the assessment the county sets. Some counties reassess after a sale, and others do not, so check your county's rules.
Can I still appeal after the deadline?
Some counties allow late appeals only in limited cases. If your deadline has passed, check your county's rules before you assume the right is gone.
The deadline is the part people miss
Appeal deadlines are set by each county, and they are often short. Look for the date on your notice, and gather your evidence before it passes.
What to ask
- What assessed value is on my notice, and how did the county set it?
- What is the total mill rate for my property, including school and local levies?
- When is the appeal deadline, and what evidence does the review board accept?
- Are there credits or exemptions I have not applied for?
Where this does not apply
The formula covers the ad valorem tax on your bill. Special assessments, such as a local improvement district, are not included. Your county tax bill is the final answer.
To see the change in dollars, use the property tax estimator. For the full monthly cost of owning, see the true cost of owning calculator. Planners and workbooks are on our shop page.
Last reviewed: November 3, 2026.
This article is general educational information, not financial, legal, tax or insurance advice.
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