Presumption of validity of determination and assessment-Employing unit’s contribution reports prima facie evidence. In any action for the collection of contributions based upon a determination and assessment by the Director, it shall be presumed that such determination and assessment has been validly made and the burden shall be upon the defendant to prove the contrary. In any hearing conducted pursuant to Sections 2200 or 2201 and in any action for the collection of contributions based upon contribution report forms issued to any employing unit and received by the Director in the regular course of his administration of this Act, such reports shall be admissible into evidence upon presentation without proof of execution and shall be prima facie evidence that the employing unit to whom such reports were issued was an employer during the period covered by such reports and of the liability of such employing unit for the payment of the amount of contributions therein set forth.