CENVAT Credit can be claimed on the basis of Documents as described in Rule 9 od Cenvat Credit Rules, 2004. Previously maintenance of RG 23 registers was mandatory for claiming CENVAT Credit. RG23 A & RG23 C were records of CENVAT credit availed & utilised. But now maintenance of such records is not mandatory.
Rule 9 (5) & (6) of the above said Rules are produced below:
"(5) The manufacturer of final products or the provider of output service shall maintain proper records for the receipt, disposal, consumption and inventory of the input and capital goods in which the relevant information regarding the value, duty paid, CENVAT credit taken and utilized, the person from whom the input or capital goods have been procured is recorded and the burden of proof regarding the admissibility of the CENVAT credit shall lie upon the manufacturer or provider of output service taking such credit.
(6) The manufacturer of final products or the provider of output service shall maintain proper records for the receipt and consumption of the input services in which the relevant information regarding the value, tax paid, CENVAT credit taken and utilized, the person from whom the input service has been procured is recorded and the burden of proof regarding the admissibility of the CENVAT credit shall lie upon the manufacturer or provider of output service taking such credit."
Hence, when required the manufacturer will have to proof the eligibility of CENVAT credit availed & utilised.
Please check the link below for more details:
https://www.cbec.gov.in/excise/cxrules/new-cenvat-rules.htm