Mass Appraisal appraises many properties at once. Mass Appraisal is typically done for property tax purposes, and the effective valuation date for all Mass Appraisals in Massachusetts is January 1st of the valuation year. A fee appraiser appraises only one property at a time. Such an appraisal is done for a specific reason, such as purchase, refinance, estate valuation, etc. The date of the appraisal is typically the day it is appraised.