Purchase Returns

Input tax credit has to be reduced in case of purchase returns.

If your supplier has issued credit note, you need to reduce that much from your eligible ITC in Form GSTR-3B. However, you don't have eligible IGST credit in the current month, negative credit cannot be entered in Form GSTR-3B. Therefore, you may have to consider in subsequent month. Request your supplier to issue credit note accordingly.

You can treat that much in inter-state outward supply and pay tax (IGST on purchase returns) that is the only way forward.