California Code, Revenue and Taxation Code - RTC § 9502

(a) Prior to imposition and collection of any tax under this part, a proposition granting authority to the county to impose the tax shall be submitted to and approved by the voters at an election. The proposition shall specify the maximum tax to be imposed and may specify the period for which the tax will be imposed.

(b) A proposition may be submitted to the voters under subdivision (a) only if (1) it is approved by the board of supervisors and a majority of the city councils of the cities having a majority of the population in the incorporated areas of the county, as provided in subdivision (c), and (2) the county and the majority of the cities having a majority of the population in the incorporated areas of the county have a written agreement with respect to allocation of the revenues between the county and the cities.

(c) If the board of supervisors approves the proposition prior to the approval of a majority of the city councils of the cities having a majority of the population in the incorporated area of the county, the approval of the other city councils to secure both of those majorities shall be secured within one year of the approval of the board of supervisors. If the board of supervisors approves the proposition after the approval of the city councils with both of those majorities, the approval of the board of supervisors shall be made within one year of the date of the approval of the city council which results in the proposition being approved by the city councils with both of those majorities.