Cal. Insurance Code § 900

(a) On or before the first day of March of each year every insurer doing business in this state shall make and file with the commissioner, in the number, form, and by the methods prescribed by the commissioner, statements exhibiting its condition and affairs as of the previous December 31. If the first day of March falls on a day other than a business day, the filing is due to the commissioner by the first business day preceding the first day of March. (b) Each year, on or before the following dates, every insurer doing business in this state shall make and file with the commissioner, in the number, form, and methods prescribed by the commissioner, statements exhibiting its condition and affairs for the period beginning on January 1 of the current calendar year through the end of each quarter of the current year as described below. These quarterly filings shall cover the period of time beginning January 1 of the current year through and including the last day of the quarter for which the report is being made. The first quarter filing shall be filed with the commissioner on or before May 15th of every year. The second quarter filing shall be filed with the commissioner on or before August 15th of every year. The third quarter filing shall be filed with the commissioner on or before November 15th of every year. If any of these dates fall on a day other than a business day, then the filing is due to the commissioner by the first business day preceding that date.