An ad valorem tax is measured by value, and property tax is the household version. A flat fee stays put when the house is worth more; this tax does not.
An ad valorem tax is a tax measured by the value of the thing being taxed, and the local property tax is the version that shows up on a homeowner's yearly bill. A flat fee does not change when the house is worth more. An ad valorem charge does. The extra dollars repeat each year the printed value stays high.
What is the difference between an ad valorem tax and a flat fee?
The IAAO glossary calls ad valorem a tax measured by value. Property tax is the everyday case. A trash hauler's flat $200 charge does not move if the roll says $200,000 or $400,000. Ten mills on $200,000 of taxable value is $2,000, and ten mills on $400,000 is $4,000.
Example: a $200,000 taxable value at 10 mills produces a $2,000 ad valorem bill. That round-number walkthrough is an example, not a county's posted rate.
Look up if you are overpaying.
Does a property tax appeal change an ad valorem tax?
A property tax appeal is aimed at the value under the rate, not at renaming the tax. If the printed value comes down, the ad valorem bill comes down with it. The property tax glossary keeps that value side next to millage. Fair Appeal reviews the property and decides whether to file, and you pay only if FairAppeal saves you money.