Illinois Assessor Reason Codes are used by assessors to explain why they are assessing a property. The codes are divided into three categories: assessment and taxation, property assessment, and exemption and tax relief. Assessment and taxation codes include the reason for the assessment, such as whether it is an original assessment or a reassessment. Property assessment codes are used to explain the basis for the assessment, such as whether it is based on a sale, an appraisal, or other factors. Exemption and tax relief codes are used to explain why a property is eligible for a tax exemption or tax relief. The codes are used by assessors to ensure that assessments are fair, accurate, and uniform across the state. The codes are also used by the public to understand the reasons behind the assessments.