Cal. Rev. & Tax. Code § 19312

Insofar as the claim for credit or refund relates to an overpayment on account of the deductibility, under Section 24348 of this code or Section 166 of the Internal Revenue Code, of a debt as one which became worthless, or a loss from worthlessness of a security under Section 24347 or 24348 of this code or Section 165(g) or 166 of the Internal Revenue Code, or an erroneous inclusion of an amount attributable to the recovery of a bad debt, prior tax or delinquency amount, under Section 111 of the Internal Revenue Code due to an adjustment of a bad debt deduction under Section 24348 of this code or Section 166 of the Internal Revenue Code, or a loss deduction from worthlessness of a security under Section 24347 of this code or Section 165(g) of the Internal Revenue Code, in lieu of the period of limitations prescribed in Section 19306, the period shall be seven years from the date prescribed by law for filing the return for the year with respect to which the claim is made.