GSTN has issued an advisory on Auto-population of e-invoice details into GSTR1.
For the month of March, 2021, the auto-population of e-invoices into GSTR-1 (of March, 2021) is still in progress and is likely to take some more time.
Hence, notified taxpayers who are reporting e-invoices, are hereby advised not to wait for the complete auto-population, and instead proceed with preparation and filing of GSTR-1 for March, 2021 (by the due date), based on actual data as per their records.
The HSN Master for download in excel format will also be published shortly on the same page.
If HSN of any Goods/Service is otherwise valid but not available in the HSN master, kindly raise a ticket on GST Self-Service Portal: https://selfservice.gstsystem.in/