A revaluation uses mass appraisal methods and techniques, meaning many properties are appraised at once. Mass appraisal is typically done for property tax purposes and the effective valuation date for all mass appraisals in Massachusetts is January 1 of the revaluation year. Meanwhile, a fee appraiser appraises only one property at a time. The appraisal is done for a specific reason, such as purchase, refinance, estate valuation, etc. The date of the fee appraisal is typically the day it is appraised.