Murrieta property owners who think their home or business lost value can ask the county for a lower tax bill, but the deadline to file is as early as Nov. 1.

Riverside County Assessor-County Clerk-Recorder Peter Aldana said Proposition 8 reduction requests must be filed by Nov. 2, according to a City News Service report published by Patch. The county assessor's website, however, lists the filing deadline as Nov. 1, 2026. Property owners should confirm the exact date with the assessor's office before filing.

A Prop. 8 reduction, named for the 1978 ballot measure, applies when a property's current market value falls below its assessed value as of the Jan. 1 lien date, the annual valuation point for property taxes. Under state law, the assessor must enroll whichever figure is lower: the property's Proposition 13 base-year value, adjusted for inflation, or its market value on that date.

The reduction is temporary.

The assessor's office reviews the property each year until the base-year value again falls below market value. At that point, normal Proposition 13 limits resume, capping annual increases at 2%.

The assessor's office said it will review thousands of properties this year, including all that received a decline-in-value reassessment last year. Owners whose properties are already part of that review do not need to file a separate application, the office said.

The office said in a statement that property owners who believe their property may qualify can submit a request for review based on their specific circumstances.

The Prop. 8 request is not the only option. Property owners who want to formally challenge their assessed value can file a separate assessment appeal by Nov. 30, 2026, the assessor's office said. If a Prop. 8 reduction is denied, owners can still take their case to Assessment Appeals officers and boards.

Riverside County's 2026 assessment roll totals $483.98 billion in net taxable value, a 5.18% increase over the prior year, according to the county. The roll covers more than one million assessments across residential, commercial, industrial, agricultural and business properties.

Aldana said in a statement that every assessment on the roll matters to property owners and the public agencies that rely on the information.

The first installment of property taxes for the current year is due Dec. 10. Filing instructions for Prop. 8 requests are available at rivcoacr.org.