Any registrant who packages or labels seed, or both, with the name and address of the person who only retails the seed within the state shall, at the time of sale to such person, collect from the person whose name and address appears on the label, the assessment due based upon the invoice price for the seed, and pay such assessment to the director, as provided by regulations. The person collecting the assessment as provided under this section may charge, collect, and retain an additional reasonable fee established by the director for handling this collection and payment.