John A. Hammer, III, Massachusetts Association of Land Surveyors and Civil Engineers, Inc
Assessors have historically warned visitors to their offices that the tax maps are not property line plans. They are an inventory of all the ownerships of land within their municipality and they approximate the geometric size and shape of individual parcels. Compiled from recorded individual subdivisions and plans of land, the maps are a composite index of a municipality's land records. No certification of the accuracy of assessors' parcel lines is ever conveyed.
Attorney General Robert H. Quinn, January 31, 1972
…the purpose of the maps is only to sufficiently describe the property in question in order to provide effective notice of which property is being taxed.