The Department, or any person authorized in writing by it, may examine the books, papers, records and equipment of any person selling tangible personal property and any person liable for the use tax and may investigate the character of the business of the person in order to verify the accuracy of any return made, or, if no return is made by the person, to ascertain and determine the amount required to be paid. (Ord. 106 §17(D), 1989)