(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.

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