GSTR 1 with only Credit note

In one month I have no IGST output tax liability, but I have a credit note IGST amounting to Rs 15000.
So As per GSTR-1, My IGST Liability is Negative 15000.
In GSTR 3B My IGST Liability is Zero.
Querry:-
How is this Negative 15000 IGST benefit reflected in the GST site?
I have checked
1. Credit Ledger - But This amount is not reflected
2. Following Months Return:- But Not adjusted with the Following month IGST output tax