Hello Aditya,
For Free goods we use R100 condition type for 100% discount.
when invoice is posted system post credit entry to Revenue account for price condition PR00 and other components in pricing as we post for normal sales invoice.
For R100 condition type system debit the account for free goods account which can be expenses account .
At the end customer will not be debited so there will be no receivables against customer.
accounting entry will look like as below
Revenue account Cr
Free goods account Dr.
Hope it will help.
ATP