Is it mandatory to put HSN or Accounting code against each item? I have read under rules that Taxpayers whose turnover is below Rs. 1.5 crores are not required to mention HSN Code in their invoices. For small businesses, falling under Composition scheme, do they need to provide complete details on the Bill of Supply (except CGST/SGST and IGST) and I assume Bill of Supply is same as Retail Invoice? Under GST filing, do we need to send the complete details of Invoice (HSN codes and items) for return calculations to GSTN?