Do I need to generate a separate GSTR- file for each month?
It depends on whether you are a monthly or a quarterly filer of Form GSTR-1.
If you are a monthly filer, then you need to generate and file a separate GSTR-1 file for each month by the 11th of the succeeding month.
If you are a quarterly filer, then you need to generate and file a single GSTR-1 file for each quarter by the 13th of the month following the quarter1. However, you can also use the Invoice Furnishing Facility (IFF) to upload your B2B invoices and credit/debit notes on a monthly basis.