In this section, you will find an explanation of the terms used in various mailings sent from the Assessor Division.

Appraised Value

A property’s value as determined by the sale amounts of comparable properties. The current appraised value is usually the property’s current market value.

Assessor’s Parcel Number

The Assessor’s identification number for a specific property. Also referred to as the account number, folio number and UPC in different regions. 

Assessed Value

The value placed on the property by the San Mateo County Assessor-County Clerk-Recorder’s Office, Assessor Division based on the property’s appraised value. The assessed value generally increases annually at a rate from 1%-2%. However, this is not necessarily the property’s current market value. 

Base Year Value

A property’s original 1975/1976 market value, or its market value at the time of its most recent change in ownership or completion of new construction.  This is then increased by up to 2% each year for inflation (ie, factored) to create a Factored Base Year Value.

Census Tract

A geographical area containing approximately 1,000-2,000 properties of a similar nature. As areas change over time due to changes in population density and other factors, the census tract boundaries may change as well. 

Cost Per Square Foot

A property’s cost per square foot, normally determined by dividing the property’s sale price by the square footage of the structure. However, this figure can be misleading. Cost per square foot does not take lot size into account and should only be used as a basis of comparison when looking at properties of similar lot size, characteristics and date sold. 

Document Number

The number assigned to a recorded document by the San Mateo County Assessor-County Clerk-Recorder’s Office, Clerk-Recorder Division. 


A limited right in a piece of land owned by another. This entitles the holder of the right to some use of the land. For instance, if Barney owns a property that is completely surrounded by Fred’s property, Barney can get an easement to build a driveway from his property to the main road. 

Factored Base Year Value (FBYV)

A property’s Base Year Value, increased by a maximum of 2% each year for inflation (ie, factored), creating a Factored Base Year Value.

Homeowner Exemption

This exemption provides the homeowner with up to a $7,000 exemption on the annual assessment of their owner-occupied residence. This can equate to roughly $70 per year in property tax savings.


Any structures that are built on a piece of land. For instance, a house built on a vacant lot is considered an improvement. 

Land Value

The actual value of the land on which a property sits. This does not include the value of the structure. 

Legal Description

The description of the property as documented by the County Recorder. Usually identifies physical location in terms of tract and lot.

Prop 8 Value

When market value is less than the Factored Base Year Value as of the lien date in any given year, a property is eligible for a temporary reduction in the taxable value for that year under Proposition 8. This temporarily reduced value is often referred to as the “Prop 8” value.  Prop 8 values are reviewed annually until the market value again exceeds Factored Base Year Value.

Prop 13 Value

Same as Factored Base Year Value.  A property’s Base Year Value, increased by a maximum of 2% each year, creating a Factored Base Year Value.

Proposition 13

Proposition 13 has been the foundation of California’s property tax system since it was passed in 1978.  Under Proposition 13, real property is reappraised only when a change in ownership occurs, or when new construction takes place. A change in ownership occurs when there is a transfer of property, whether the transfer is a purchase, a gift, an inheritance, a foreclosure, the addition or deletion of an owner or any other means. New construction is any improvement to property that is not normal maintenance.

Tax Amount

The annual property tax as determined by the assessed value and tax rate. 

Tax Rate Area

An area within a county that is taxed at a particular rate, usually resulting from the number of public services in the area such as fire and police protection. 


All of the elements that constitute the legal right to own, possess, use, control, enjoy and dispose of real estate. 

Title Company

The entity that insures the title for the owner of the property. 

Title Insurance

Protects the owner or other insured, such as a lender, against loss or impairment of title. 

Transfer Date

The date the sale of the property is recorded. 

Use Code

The code that indicates how a property is being used.