Cal. Pub. Util. Code § 6299

The grantee shall file with the clerk of the municipality, within three (3) months after the expiration of the calendar year, or fractional calendar year, following the date of the granting of the franchise and within three (3) months after the expiration of each calendar year thereafter, a verified statement showing in detail the total gross receipts of the grantee, its successors, or assigns during the preceding calendar year or fractional calendar year from the sale of the utility service for which the franchise was granted.