The assessor starts with the value of the land by purchase price. When you pull a building permit the assessor gets a partial copy of the plans. Sometimes they do progress checks to get the value up to date for the next assessment period. When the project is finished the owner submits a statement of the nature and quality of improvements and puts a price on it. The Assessor takes all this in to consideration and makes a final assessment and this is the tax base. I personally have always come out better according to the assessor’s work than if I had purchased a similar property.That may not always be the result. I don’t really Know.