GST Tax Invoices

Supplier uploaded  Tax Invoices in GSTR -1  but actually sales return happened  in the same month. Supplier did not  uploaded credit note for that Month.  But Purchaser not accounted  Tax invoices and do not made payment to the supplier and did not claim input tax for that month. GST Department has issued notice to the Buyer short declaration of Sales. How to handle this situation in favor of Buyer???

Regards

Manjunath