law: 39. Memoranda of sales.
  If a registered dealer
  (a) sells goods to another registered dealer, or
  (b) makes sales in the course of inter-State trade or commerce, or
  (c) sells any goods exceeding ten rupees in value in any one transaction to any other person,
  he shall issue to the purchaser a bill or cash memorandum serially numbered, signed and dated by him or his servant, manager or agent and showing therein his name and address and such other particulars as may be prescribed and he shall keep a duplicate or copy of such bill or cash memorandum duly signed and dated and preserve it for a period of not less than five years from the end of the year unless any proceedings in respect of that year are pending in which case they shall be preserved till the final decision in those proceedings:
  Provided that if in respect of any goods or class of goods or any dealers or class of dealers, the Administrator is of the opinion that it is not practicable to issue any bills or cash memoranda for sale of goods exceeding ten rupees in value in any one transaction to any other person, he may, by notification in the Official Gazette,
  (i) specify such amount exceeding ten rupees in value as the amount for the issue of such bills or cash memoranda;
  (ii) exempt such goods or class of goods or dealers or class of dealers from the operation of this section.