Cal. Food & Agric. Code § 32793

The director shall provide blanks for reporting statistics on milk and milk products and on products resembling milk products. He shall, on or before the first of each month, cause to be mailed to each person that is engaged in operating any milk products plant, any plant in which products resembling milk products are manufactured, and to each market milk distributor such number of the blanks as may be necessary. Each person that is engaged in operating any such plant, or that is a market milk distributor shall, within 30 days after the blank is mailed to him, transmit to the director a full and accurate report of the amount of milk and milk products and products resembling milk products which he produced, purchased, manufactured or distributed during the preceding month.