State Controller
https://www.sco.ca.gov/ardtax_public_auction.html
Property becomes tax-defaulted land if the property taxes remain unpaid at 12:01 a.m. on July 1st. Property that has become tax-defaulted after five years (or three years in the case of property that is also subject to a nuisance abatement lien) becomes subject to the county tax collector’s power to sell in order to satisfy the defaulted property taxes. The county tax collector must attempt to sell the property within four years of becoming subject to sale. The county tax collector may offer the property for sale at public auction, a sealed bid sale, or a negotiated sale to a public agency or qualified nonprofit organization.
Public auctions are the most common way of selling tax-defaulted property. The auction is conducted by the county tax collector, and the property is sold to the highest bidder.
Pursuant to California Revenue and Taxation Code (RTC) section 3700.5, the county tax collectors are required to notify the State Controller's Office "not less than 45 days nor more than 120 days before the proposed sale." Additionally, RTC section 3702 requires the tax collector to publish the intended sale three times in a newspaper of general circulation within the county, at least three weeks prior to the tax sale.