Why is the assessed value different from the estimated value?

The assessed value is the best valuation of a property when it is just updated after a sale or upon an assessor visiting the property to do an assessment. This is the value that the property tax is based on, but it is frequently anchored to whenever the property was last assessed with a potential annual percentage change based on inflation or other local market factors. As time goes on, this value becomes less accurate to the current market conditions, but is the best representation of the property value when it is newly updated by an appraiser. 

The estimated value is a modeled value of a property that is based on local market conditions and is updated frequently. This information maybe accurate for the current market, but is not a substitute for an appraisal.