Every distributor or secondary distributor who is required to procure a license under this Act and who purchases cigarettes for shipment into Illinois from a point outside this State shall procure invoices in duplicate covering each such shipment, shall make the invoices available for inspection upon demand by a duly authorized employee of the Department, and shall, if the Department so requires, furnish one copy of each such invoice to the Department at the time of filing a return or a report required by this Act.