Cal. Rev. & Tax. Code § 19701.5

(a) Any person who signs his or her spouse’s name on any income tax return, or any schedules or attachments thereto, or who files electronically pursuant to Section 18621.5, without the consent of the spouse as provided in subdivision (b), is guilty of a misdemeanor and shall upon conviction be fined an amount not to exceed five thousand dollars ($5,000) or be imprisoned for a term not to exceed one year, or both, at the discretion of the court, together with costs of investigation and prosecution.
(b) Notwithstanding subdivision (a), any person who signs his or her spouse’s name shall not be guilty of a misdemeanor when one spouse is physically unable by reason of disease or injury to sign a joint return, and the other spouse, with the oral consent of the one who is incapacitated, signs the incapacitated spouse’s name in the proper place on the return followed by the words “By ____, Spouse (or Husband or Wife),” and by the signature of the signing spouse in his or her own right, provided that a dated statement signed by the spouse who is signing the return is attached to and made a part of the return stating each of the following:
1. (1) The name of the return being filed.
2. (2) The taxable year.
3. (3) The reason for the inability of the spouse who is incapacitated to sign the return.
4. (4) That the spouse who is incapacitated consented to the signing of the return and that the taxpayer and his or her agent, if any, are responsible for the return as made and incur liability for the penalties provided for erroneous, false, or fraudulent returns.
(c) The penalties provided by this section are cumulative and shall not be construed as restricting any other penalty provided by law based upon the same facts, including any penalty under Section 470 of the Penal Code. However, an act or omission which is made punishable in different ways by this section and different provisions of the Penal Code shall not be punished under more than one provision.