The major source of revenue for the 351 cities and towns in Massachusetts is the property tax. The property tax is an "ad valorem" (based on the value) tax. The tax is apportioned to individual properties based on the value of the property. In Massachusetts, estimates of the value are called assessments. The assessments of a large number of parcels for property tax purposes constitute a highly specialized field of appraisal. In Massachusetts, the property tax is assessed on real and personal property to the owner of record as of January 1.