Section 21 in The Companies (Cost records and audit) Rules, 2014
21. By-Products and Joint Products.-
a) Proper records shall be maintained for each item of by-product, if any, produced showing the receipt, issues and balances, both in quantity and value. The basis adopted for valuation of by-product for giving credit to the respective process shall be equitable and consistent and should be indicated in cost records. Records showing the expenses incurred on further processing, if any, and actual sales realisation of byproduct shall be maintained. The proper records shall be maintained in respect of credits or recoveries from the disposal of by-products.b) The cost up to the point of separation of products or services shall be apportioned to joint products or services on reasonable and equitable basis and shall be applied consistently. The basis on which such joint costs are apportioned to different products or services arising from the process shall be indicated in the cost records. Proper records shall be maintained in respect of credits or recoveries from the disposal of joint products or services.
