(1) The papers relevant to the making of an assessment in respect of any particular dealer shall form an assessment case record, and shall be arranged in two separate classes of files 'A' and 'B' which shall be kept together. The 'A' class file shall contain important papers such as order sheets, returns, challans, notices, assessment orders, documents, copies of decisions on appeal or revision. The 'B' class file shall contain the declarations and all other papers like rough calculations, enquiries from other sources.

(2) The 'A' and 'B' class files shall be preserved for five calendar years from the date of the final disposal of the case.