California Code, Revenue and Taxation Code - RTC § 18861

(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 Cancer Research Voluntary Tax Contribution Fund, pursuant to Section 18862.This designation is to be used as a voluntary contribution on the tax return.

(b) The contributions shall be in full dollar amounts and may be made individually by each signatory on a joint return.

(c) A designation under subdivision (a) 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) If an individual designates a contribution to more than one account or fund listed on the tax return, and the amount available is insufficient to satisfy the total amount designated, the contribution shall be allocated among the designees on a pro rata basis.

(e) The Franchise Tax Board shall revise the forms of the return to include a space labeled the “California Cancer Research Voluntary Tax Contribution Fund” to allow for the designation permitted under subdivision (a). 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 causes, detection, and prevention of cancer, to expand community-based education on cancer, and to provide prevention and awareness activities for communities that are disproportionately at risk or afflicted by cancer.

(f) A deduction shall be allowed under Article 6 (commencing with Section 17201) of Chapter 3 of Part 10 for any contribution made pursuant to subdivision (a).