Section 11(2)(c) in The Bihar Electricity Duty Rules, 1949
(c)The said certificate in respect of any month shall be in triplicate and shall be provided to the preceding seller before the expiry of the fifteenth day of the month following the month to which it relates. The copy marked "Counterfoil" shall be retained by the subsequent seller issuing the certificate and the copies marked "Original" and "Duplicate" shall be made over to the preceding seller who shall annex the copy marked "Duplicate" and shall enclose the copy marked "original", with his return for the subsequent month.