Mo. Rev. Stat. § 149.170: Filing of return, remittance of amounts, required, when — rules — maintenance of records.

1. Each person responsible for the payment of the taxes levied in section 149.160 shall file a return and remit amounts owed monthly to the director of revenue on or before the fifteenth day of the month following the first sale within the state. From every remittance to the director of revenue made on or before the date when the same becomes due, the person required to remit the same shall be entitled to deduct and retain an amount equal to two percent thereof.

2. The director shall promulgate reasonable rules and regulations governing collection and administration of the taxes levied under section 149.160, including such record keeping requirements as will enable the director to determine that all amounts owed are remitted when due. All of the records required by rule of the director to be maintained by persons responsible for the payment of the taxes levied in section 149.160 shall be retained by such persons for a period of three years following the due date of taxes on merchandise represented by such records. During the three-year period, the director shall have the right to conduct reasonable inspections and audits of such records.