Cal. Rev. & Tax. Code § 5146
If all or any portion of the taxes sought to be recovered were collected by officers of the county for a city or cities, an action must be brought against the county for the recovery of those taxes. When an action is filed against a county for taxes collected by the county on behalf of a city or cities, the county shall give notice of that action to the city or cities within 30 days of the county's receipt of the summons and complaint. A fee shall be payable by the assessee in an amount prescribed by the court to cover the reasonable costs incurred by a county or counties in giving the required notice. Any city receiving notice of the action filed against the county may, within 30 days of the receipt of that notice, intervene in that action. Whether or not a city intervenes in the action, any judgment rendered for an assessee shall be entered exclusively against the county; however, the county shall be entitled to recover separately from the city or cities and other tax entities those taxes collected by the county on behalf of the city or cities and other tax entities which are subject to refund to the assessee as a result of the judgment. Payment to the taxpayer upon the judgment and any interest thereon may be deferred by the county until the apportionment of property tax revenue next following the date of the judgment, or as the county and the taxpayer may otherwise agree.
Interest shall accrue during any deferral period unless the county and taxpayer otherwise agree. The county may if it chooses to do so offset the amount of the judgment and interest recoverable by it from the city or cities and other tax entities against amounts held in the county treasury therefor or against amounts due and payable thereto, including, but not limited to, property tax apportionments.
The amount of the fee required by this section shall not be recoverable by the assessee in the action and no judgment entered in the action in favor of the assessee shall provide for the recovery of the fee.
As used in this section, "county" includes a city and county.
If all or any portion of the taxes sought to be recovered were levied on state-assessed property, property which the board has found ineligible for the welfare exemption pursuant to Section 254.5, or property as to which the board has reviewed the assessment pursuant to Section 11 of Article XIII of the Constitution, the board shall be joined as a party to the action.
Ca. Rev. and Tax. Code § 5146