If any person fails or refuses to make a return, either in whole or in part, or if the Mayor and City Treasurer have reasonable grounds to believe that any return made is deficient so as not to form the basis of a satisfactory assessment of the tax, they may proceed as they deem best to obtain information on which to base the assessment of the tax. The Mayor and City Treasurer may by themselves or by their duly appointed agent make an examination of the books, records and papers, and audit the accounts of any such person, and may take the evidence, on oath administered by them or their agent, of any person whom they may believe shall be in possession of any relevant information. As soon as possible after the procuring of such information as they may be able to obtain as to any person failing or refusing to make a return, the Mayor and City Treasurer shall proceed to assess the tax and shall notify the person assessed of the amount of the tax. The assessment of the tax by the Mayor and City Treasurer shall be final as to any person who refused to make a return. (8-9-71)