Here is the answer, 2 Baozi, if you find the information usefull.
The assessment value for tax purpose is usually certain percentage of the
market price, the percentage can be 50 to 100%, it depends on the twonship.
For example, it is 80% for where I live. You can estimate this information
by comparing the selling price and theassessment value of some recent sales
in your township.
The property tax is the assessment value times the tax rate of your township
, it shall be fixed number every year.
For appeal purpose, you need do a apprasial on your property, and then your
assessment value shall be the apprasial value (sale value) times the
percentage. For example, if the apprasial value is 500K, percentage is 80%,
then you shall appeal for 400K as the assessment value.
It is also very helpful, to find the assessment values of similar houses in
your nearby area, and appeal for the assessment values as the comparable
properties.