Cal. Pub. Util. Code § 587

Every water corporation with more than 2,000 service connections, and every electrical, gas, and telephone corporation shall annually prepare and submit to the commission a report describing all significant transactions, as specified by the commission, between the corporation and every subsidiary or affiliate of, or corporation holding a controlling interest in, the water, electrical, gas, or telephone corporation. The report shall identify the nature of the transactions and the terms and conditions applying to them, including, but not limited to, the basis upon which cost allocations and transfer pricing were established for the transactions.