Cal. Rev. & Tax. Code § 11005.6
Any city, county, or city and county may apply to the Demographic Research Unit of the Department of Finance to estimate its population. The department may make the estimate if in the opinion of the department there is available adequate information upon which to base the estimate. Not less than 25 days nor more than 30 days after the completion of the estimate, the Department of Finance shall file a certified copy thereof with the Controller if the estimate is greater than the current certified population. Such a certification may be made once each fiscal year.
All payments under Section 11005 for any allocation subsequent to the filing of the estimate shall be based upon the population so estimated until a subsequent certification is made by the Department of Finance or a subsequent federal decennial census is made.
Population changes based on a federal or state special census or estimate validated by the Department of Finance shall be accepted by the Controller only if certified to them at the request of the Department of Finance. The request shall be made only if the census or estimate is greater than the current certified population and shall become effective on the first day of the month following receipt of the certification.
The Department of Finance may assess a reasonable charge, not to exceed the actual cost thereof, for the preparation of population estimates pursuant to this section, which is a proper charge against the city, county, or city and county applying therefor. The amount received shall be deposited in the State Treasury as a reimbursement to be credited to the appropriation from which the expenditure is made.
As of May 1, 1988, any population estimate prepared by the Department of Finance pursuant to Section 2227 may be used for all purposes of this section unless a written request not to certify is received by the department from the city, city and county, or county within 25 days of completion of the estimate.
Ca. Rev. and Tax. Code § 11005.6