California Code, Revenue and Taxation Code - RTC § 46163

(a) Any return, declaration, statement, or other document required to be made under this part that is filed using electronic media shall be filed and authenticated pursuant to any method or form the board may prescribe.

(b) Notwithstanding any other law, any return declaration, statement, or other document otherwise required to be signed that is filed by the taxpayer using electronic media in a form as required by the board shall be deemed to be a signed, valid original document, including upon reproduction to paper form by the board.

(c) Electronic media includes, but is not limited to, computer modem, magnetic media, optical disk, facsimile machine, or telephone.