Sir, In gstr1 of august 2017 by mistake we have uploaded the b2b invoice twice like bill no. Gst-150 and second time 150. date and amount of twice uploaded bills are exactly matched with and some of our customers claim the ITC of both bills. can the customer claim the ITC only on the basis of 2a whether he has an original invoice or not and makes the payment to a supplier or not? now the department has raised the demand notice of the differential amount of tax (gstr3b vs gstr1). now, what can we do to avoid the tax penalty? is the differential amount of tax is payable by us or the customer who claims the ITC without bills and without payment. in this case, what should we do to avoid the tax penalty? please guide me.