IN GSTR-3B RETURN , NEGATIVE OUTWARD SHOWN AS ITC AND - VE INWARD SHOWN AS OUTWARD

In july 2017, my client purchase intra-state and sales inter-state.
In Aug 2017, there is no purchase and sales, but whole interstate sales return, hence, whole purchase return to intrastate supplier.
Due to no (-) ve amount to be shown in GSTR-3B return.
we had shown purchase return as sales and sales return as purchase.
in GSTR-1, credit note for sales return taken into consideration.
Pl.suggest ,where to show such types of itemd in GSTR-9 return.