The Assessor is responsible for determining the assessed value of all taxable property located in San Mateo County. With approximately 237,000 assessments each year, the Assessor Division creates the official record of taxable property (local assessment roll), shares it with the County Controller and Tax Collector, and makes it publicly available. The local assessment roll is determined by identifying, mapping, inspecting, and calculating the assessed value for all real (land and structures) and business properties. Typically, property tax is 1% of the assessed value, plus an amount to amortize voter-approved bonds and any fees for special assessments or charges such as mosquito abatement or sewer fees.

The division assesses over 221,000 units on the secured roll and 16,000 units on the unsecured roll. In addition, the Office processes approximately 50,000 transfer documents, 24,000 building permits, 143,000 exemptions and 10,000 business property statements annually.

San Mateo County claims within its boundaries a wealth of land, buildings, and taxable properties with an assessed value of more than $206 billion. The property tax revenues generated from these assets are vital to maintaining local government operations and public services.

San Mateo County - Combined Property Assessment Roll - Historical Values

For more information, please read 2018-2019 Assessor's Annual Report.


Real Property

Real Property Assessment

The Assessor Division compiles a roll of property tax assessments for delivery to the County Controller by July 1 each year. This “Local Assessment Roll” covers more than 237,000 assessments countywide, value in excess of $206 billion.

A copy of the Local Assessment Roll is available at the Assessor Division front counter for public inspection. The Assessor Division also reassesses personal property each year.


Business Personal Property

The Assessor sets the value of the tangible assets possessed by more than 15,000 businesses operating in San Mateo County, thereby establishing their taxable value. The Assessor also sets the value of 4,000 boats and 400 private aircraft owned here.

Private citizens get answers to questions about their property from the Assessor. These include how to file business personal property statements and, through the County Clerk, how to file fictitious business name statements.


Online Services

The Assessor Division offers a variety of online services to make information access and submission quicker and more efficient.


Assessment Roll Summaries

Secured, Unsecured and Combined Roll Summaries

The assessment roll is a listing of assessed property within the county. It includes some identifying features such as a parcel or account number, the assessed owner, and a breakdown of the assessed values and exemptions.The summary is a breakdown by cities and unincorporated areas of the county.


Glossary of Terms

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.