Treatment of Recovered Material

My question is as follows:- Product KBR recovered from manufacturing process of product A Product NABR recovered from manufacturing process of product B Product LIQUID BROMINE recovered from distillation of product KBR and also from NABR LIQUID BROMINE is also used as an INPUT of PRODUCT A. Presently Inventory Record of KBR & NABR is maintined as a work in process (W.I.P) now my question is whether present system of maintaining record is CORRECT. or, KBR & NABR should be recorded as FINISHED GOODS and then issue as Input Material for recovery of LIQUID BROMINE. and is there any requirement for issuing of INVOICE as per CENTRAL EXCISE FOR CAPTIVE CONSUMPTION.