A township assessor is an elected official who is responsible for determining the market value of most real property in the assessment jurisdiction. This valuing of a multitude of properties or mass appraisal is accomplished by using standard methods, while allowing for statistical testing. After determining market value, the property is then assessed at one-third (1/3) of that value. 

The assessed value is used to apportion the tax burden over all property owners. All local governments, townships, schools, forest preserve districts, park districts, libraries, etc. receive their income from taxes levied against property values as appraised by the township assessor. 

It is important to note that an assessor does not collect taxes, or determine the tax rate. The assessor is concerned with value, not taxes. The assessor appraises all properties as of January 1, of the tax year. Reassessments are required by statute every four years. This is known as the quadrennial assessment. The statutes allow an assessor to reassess any and all properties each year where necessary. 

This annual reassessment is encouraged by the Taxpayers Federation of Illinois and the International Association of Assessing Officers (IAAO). St. Charles Township follows this yearly reassessing practice. Annual reassessments allow the assessor to react more quickly to market changes and also leads to quality, more uniform values throughout the township.