Generation of e-invoice is mandatory for certain class of taxpayers, as notified by the Government. These taxpayers are required to prepare & issue their e-invoices by reporting their invoice data in the prescribed format (e-invoice schema in FORM GST INV-01) and reporting the same on the Invoice Registration Portal (IRP). Invoices reported successfully on the IRP are given a unique Invoice Reference Number (IRN). The documents (invoices, debit notes, credit notes) reported on the IRP are then transmitted electronically to the GST system and are auto-populated in the respective tables of GSTR-1.
Source Taxguru
