Cal. Revenue and Taxation Code § 11553.5

(a) The limitation period specified in Section 11553 shall be suspended during any period of a person’s life that the person is financially disabled. (b) (1) For purposes of subdivision (a), a person is financially disabled if the person is unable to manage his or her financial affairs by reason of medically determinable physical or mental impairment of the person which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months. A person shall not be considered to have an impairment unless proof of the existence thereof is furnished in the form and manner as the board may require. (2) A person shall not be treated as financially disabled during any period that the person’s spouse or any other person is authorized to act on behalf of the person in financial matters. (c) This section applies to periods of disability commencing before, on, or after the effective date of the act adding this section, but does not apply to any claim for refund that (without regard to this section) is barred by the operation or rule of law, including res judicata, as of the effective date of the act adding this section.