National Internal Revenue Code (NIRC)
Section 241. Exhibition of Certificate of Payment at Place of Business. - The certificate or receipts showing payment of taxes issued to a person engaged in a business subject to an annual registration fee shall be kept conspicuously exhibited in plain view in or at the place where the business is conducted; and in case of a peddler or other persons not having a fixed place of business, shall be kept in the possession of the holder thereof, subject to production upon demand of any internal revenue officer.