Upcoming Deadlines to Dispute California Property Tax Valuation for 2025

For California property owners that could potentially reduce their property taxes with a decline-in-value assessment appeal, the property tax assessment appeals for 2025 are due by either September 15 or December 1 depending on the county.

Due to the dramatic declines in a number of commercial, industrial, and multifamily real estate values since 2020, many California property owners may be able to significantly reduce their property taxes by seeking a decline-in-value assessment appeal of the property tax assessed value. Depending on the county, the deadlines for filing assessment appeals are September 15, 2025 or December 1, 2025 (since November 30 falls on a Sunday). No extensions of time are available to file assessment appeals.

Proposition 13 requires county assessors to reassess real property upon a change of ownership or completion of a new construction or renovation. However, Proposition 8 allows property owners to seek a reduction in the assessed value if the property has suffered a decline in value. The value is determined based on the January 1, 2025 value for the July 1, 2025–June 30, 2026 tax year.

For 2025, the due dates for each county, as provided by the California State Board of Equalization, are as follows:

Property owners who believe that their property is currently assessed at higher than fair market value may significantly benefit from a decline-in-value assessment appeal. Taxpayers seeking a reduction in the assessed value should be careful to file any assessment appeals by the applicable deadline for their county.