Cal. Rev. & Tax. Code § 8755

The board, if it deems it necessary in order to ensure payment of the tax imposed by this part, or to facilitate the administration of this part, may require returns and payment of the tax to be made for designated periods other than quarterly periods. On or before the last day of the calendar month following each designated period, a return for the preceding designated period shall be filed with the board in any form as the board may prescribe.