An assessor is a specialist who calculates the value of property. The value calculated by the assessor is then used as the basis for determining the amounts to be paid or assessed for tax or insurance purposes.
In local government in the United States, an assessor, also called a tax assessor, is an appointed or elected official charged with determining the value of each taxable property in a county, municipality, or township; this information is then used by the local governments to determine the necessary rates of taxation to support the community's annual public budgets. (This is a specialization of the previous sense; a person who performs similar work for a private employer is more often called an appraiser or, specifically in the insurance industry, an adjuster.) In Florida, this official is known as the property appraiser. In Vermont, this office is known as a lister.