(a) An individual may designate on the tax return that a contribution in excess of the tax liability, if any, be made to the Prevention of Animal Homelessness and Cruelty Voluntary Tax Contribution Fund established by Section 18901.9.1. That 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 a taxable year on the original return for that taxable year and once made is irrevocable. If payments and credits reported on the return, together with any other credits associated with the taxpayer’s account, do not exceed the taxpayer’s liability, the return shall be treated as though no designation has been made.