California Code, Revenue and Taxation Code - RTC § 7659.93

(a) Any return, report, 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, report, 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.

(d) Upon written approval of the board, a person may satisfy the requirements of subdivision (a) by executing and providing to the board a consent and authorization for the Internal Revenue Service to provide to the board under Section 6103 of the Internal Revenue Code, the return filed by the person under Section 48.4101-2 of Title 26 of the Code of Federal Regulations. The board, in its sole discretion, may rescind its approval and require a person to file reports as specified in subdivision (a).