To assess real estate correctly, the assessor must have complete maps of all property in the jurisdiction, updated regularly to show changes in parcel boundaries or other physical characteristics.
Tax maps are an essential tool in the development and maintenance of an equitable assessment system. They are indispensable in inventorying all properties in the county and assuring their inclusion on the tax roll. They are essential for the location and identification of properties to be assessed, and are a requisite for determination of dimensions and area necessary in calculating land valuations.
A tax map, as defined in The Glossary for Property Appraisal and Assessment, is "A scale map displaying property ownership boundaries and showing the dimensions of each parcel with related identifiers, survey lines and easements."