Cal. Rev. & Tax. Code § 17506

The provisions of Section 403 of the Internal Revenue Code, relating to taxation of employee annuities, shall be modified to provide that the basis of any person in an employee annuity shall include the amount of any contributions made prior to January 1, 1987, which were not allowed as a deduction under former Sections 17503 and 17513 of the Revenue and Taxation Code (including predecessor Section 17524 repealed by Chapter 488 of the Statutes of 1983) relating to special limitations for self-employed individuals.