Captive consumption

I need help in my 2 question :

01. We are manufacturer of Lub in India, Some of the FG products which are produced in the previous yr or month, are being consumed as captive and another product is being made. We are in SAP so there is no provision of preparing a invoice for captive & paying of a duty.

02. In ER-1 return we calculate captive as

Op. Stock + Production - (Sales+Captive Consump) = Closing Stock

is it the correct procedure.

rgds

PK