Cal. Rev. & Tax. Code § 18793

(a) Any individual may designate on the tax return that a contribution in excess of the tax liability, if any, be made to the California Breast Cancer Research Voluntary Tax Contribution Fund, which is established by Section 18794. This designation is to be used as a voluntary contribution on the tax return.

(c) A designation shall be made for any taxable year on the original return for that taxable year, and once made shall be irrevocable. In the event that payments and credits reported on the return, together with any other credits associated with the individual’s account, do not exceed the individual’s liability, the return shall be treated as though no designation has been made.

(d) The Franchise Tax Board shall revise the forms of the return to include a space labeled the “California Breast Cancer Research Voluntary Tax Contribution Fund” to allow for the designation permitted. The forms shall also include in the instructions information that the contribution may be in the amount of one dollar ($1) or more and that the contribution shall be used to conduct research relating to the cure, screening, and treatment of breast cancer.