Cal. Rev. & Tax. Code § 32251

The tax is a direct obligation of the taxpayer and is due and payable monthly on or before the 15th day of each calendar month. Each taxpayer, on or before the 15th day of each month, shall file a tax return for the preceding calendar month, using electronic media, showing the amount of beer or wine or distilled spirits sold in this state, the amount of tax for the period covered by the return, and any other information as the board deems necessary. The taxpayer shall deliver the return, together with a remittance of the amount of tax due, to the office of the board on or before the 15th day of the month. Returns shall be authenticated in a form or pursuant to methods as may be prescribed by the board.