It is unlawful for any person liable to tax under this chapter to fail or refuse to make application or return for a license or to pay the fee or tax or installment thereof when due or for any person to make any false or fraudulent application; or in connection with, any such application or return; or to aid or abet another in any attempt to evade payment of the fee or tax, or any part thereof; or for any person to fail to appear and/or testify in response to subpoena issued pursuant hereto, or to testify falsely upon any investigation of the correctness of a return; or, upon the hearing of any appeal, or in any manner, to hinder or delay the city or any of its officers in carrying out the provisions of this chapter. [Code 1980 at § 15.04.170].