I definitely understand your concern that the recent tax bill you received may appear to reflect a reduced property value - however I can assure you that is not the case. Property taxes are determined by the county by an unknown algorithm, and they don't reflect improvements to your home that certainly add value.
My understanding of property tax assessments is that they are designed to allocate property tax responsibilities as fairly as possible among property owners, however, they don't accurately reflect the market value of a property.
As a general rule, as long as your tax assessed value is less than the market value of your home, you are in good shape! This means that you are actually saving a little money every year, because if your tax assessed value matched the market value, your tax bill would be higher.
I would not worry about the exact number, it will fluctuate up and down depending on area wide real estate trends (and the number of assessment appeals the county receives), and the county budget.
Zillow and Redfin use a different algorithm than the counties' tax assessors, and their estimates are typically a little bit closer to the market value. Since interior condition varies and there are other features that are not accounted for, it isn't possible for these computer generated estimates to take into consideration all of the factors that go into determining the value of a home.
If you are interested in knowing more about the value of your home, we can provide you with your own custom report with accurate up-to-date information.