The floorstocks tax report required by Section 12-28-530(A) must be accompanied by payment of the floorstocks tax calculated in accordance with Section 12-28-530(B). Payment must be made on or before the due date of that report. The floorstocks tax imposed on inventory held outside of the bulk transfer system on the effective date of this chapter reportable under Section 12-28-530(A) is payable in two equal annual installments beginning twelve months after the effective date of the act. However, a person may pay the full amount due with a timely filed return and may take a fifteen percent discount.