There will be no.of changes in invoicing post-GST – 1. Invoice will have to be Serial No. 2. ED/ST/VAT/CST codes will be replaced by CGST, SGST and IGST. 3. Registration No. of both supplier and recipient have to be given. Apart from these Advance receipt has to be collected from any person to whom advance is made. Refund voucher in case of cancellation of advance to be issued. Further delivery challans can also be issued in lieu of invoices in selected case.