406.01: Sources of Comparable Market Data

The appraiser's opinion of market value is no better than the reliability of the comparable data that is used; therefore, the appraiser must exercise due diligence to ensure the reliability of the comparable sales data that he or she uses.  The appraiser must report his or her data and/or verification source(s) for each comparable sale on the appraisal report form.  An appraiser may use a single source for the data and verifications or multiple sources if they are needed to adequately verify the comparable sales.  The quality of the data available varies from source to source and from one locality to another.  In view of this, a single data source may be adequate if the appraiser uses a source that provides quality sales data that is confirmed or verified by closed or settled transactions.  On the other hand, if the appraiser's basic data source does not confirm or verify the sales data, the appraiser will need to use additional sources.  When comparable sales data is provided by a party that has a financial interest in either the sale or financing of the subject property, the appraiser must reverify the data with a party that does not have a financial interest in the subject transaction.