Any remaining tax imposed on transactions occurring during a calendar month shall be due and payable on or before the twentieth day of the following month, except as provided in subsection (i). Underpayments of estimated taxes due and owing the department are not subject to a penalty under section 63(a) of this chapter.
However, if the importer and the importer's reseller have previously entered into a tax precollection agreement as described in subsection (j), and the agreement remains in effect, the supplier with whom the agreement has been made shall become jointly liable with the importer for the tax and shall remit the tax to the department on behalf of the importer. This subsection does not apply to an importer with respect to imports in vehicles with a capacity of not more than five thousand four hundred (5,400) gallons.
IC 6-6-2.5-35