Decline in Market Value (Proposition 8)

When an economic downturn occurs, it may affect the local real estate market causing housing and commercial values to drop. The law provides property tax relief to property owners if the value of their property falls below its assessed value.

Generally, property is assessed at the lesser of two values: 

  1. the factored base year value (typically the purchase price adjusted annually for inflation, not to exceed 2 percent per year) or
  2. current value on January 1. 

If the market value is the lesser value, the Decline in Value Assessment Program (Proposition 8) allows for a temporary reduction in assessed value.

The assessed value of a property should never be higher than the property’s value on the open market. Occasionally, market forces and other factors will cause a property’s value to decline significantly enough to create that situation. In these cases, the Assessor may lower the assessed value of any real property if it is higher than the market value as of January 1.

Each case is reviewed individually at the request of the property owner. The Assessor considers both land and improvements when determining the  January 1 market value.

If a property is enrolled in the Decline in Value Assessment Program, its assessed value is subject to annual review in subsequent years in light of current economic and market factors. For example, the assessed value may be:

  • increased to no more than the “factored base year value”, or
  • held at the prior year’s assessed value, or
  • reduced further.

The Decline in Value request should not be confused with the more formal filing of an Assessment Appeal.

Proposition 8 Assessed Value Increases Exceeding Two Percent (Restoration)

Some San Mateo County property owners whose properties were in the Decline in Value Assessment Program may see an increase (restoring to factored base year value) in their assessment values by more than two percent (2%).

Note: Although Proposition 13 expressly limits annual increases in a property’s “factored base year value” to no more than two percent per year, there is no such limitation on annual increases to a property’s assessed value in the Proposition 8 program, as long as the factored base year value is not exceeded. The deadline to request an informal review was October 31, 2023.

If the property owner does not agree with their property’s 2023 assessed value, they may file a formal appeal with Assessment Appeals Board (AAB) till November 30, 2023. The Assessment Appeals Board (AAB) was established to resolve property valuation disputes between the taxpayers and the Assessor's Office. AAB’s filing deadline schedule for 2023 assessment appeals for regular assessment is from July 2, 2023 through November 30, 2023.

The Assessor Division will accept informal Decline in Value applications for the property’s January 1, 2024 assessed value starting January 1, 2024.