Good question, frequently asked by buyers. As it was mentioned in other answers, there is no connection between the two in terms of the approach used to determine them.
But to answer your question as it was asked, it could be the the date of the last sale.
In Tompkins County, Department of Assessment typically matches assessed value to the purchase price of the last sale of the property soon after the sale. Therefore, if property was sold recently, assessed value is somewhat the same, but if property wasn't for sale for long time, assessed value can be substantially lower than current market value of the property, given, of course, property values appreciate. Hope it helps.
We are doing some very interesting statistics in our office on the assessment in certain neighborhoods in the Tompkins County area and are I am sure you would find these quite interesting. Let me know if you would like a copy ,
Bonnie Nault , 607-215-6195
This is an often misunderstood concept....
There should be no connection between the assessed value of a property and the asking price. The assessed value is a taxation department created number that is used to generate the annual tax rate.
Now, if you were talking about the appraised value there would/should be a very close relationship between that number and the sale price.