Hi,
You Query involves two questions 

1. Whether GST needs to be included in sales?
2. Whether Indirect Income needs to be included for calculation of Turnover for applicability of 206H(1C)?

The replies to above questions are below:-

1. CBDT has not clarified this point but same issue is involved in the case of computing turnover for the purpose of section 44AB. There also CBDT is silent as of now, But to our understanding GST should not form the part of the sales since it is an indirect tax collected and credited to the separate account apart from the sales which is clearly identifiable. Only in case of composite dealer since GST is not collected from the customer, it forms the part of the sales and hence needed to be included in Turnover.
2. The explanation to Section 206C(1H) used the wordings sales, gross receipts or turnover which should be read in connection with each other, meaning thereby only sales or gross receipts needs to be considered and not any indirect income and also there is a reason to do that since it is a tax collected on sales consideration and no relation with any other income, so to our knowledge and understanding no other income apart from that needs to be considered.