In my opinion also, TCS should be collected on value including GST. regarding other sections no circular issued. but as circular issued for TDS on value exclusive of GST. So, dept. may have a view that TCS on value including gst should be collected.
GST is different and tcs/tds is different. GST is form part of CBEC and TDS/TCS relates to CBDT. As I have done in some cases, both TDS and GST be deducted separately, and separate return will be filled, that will be called TDS/TCS return and GST return.
There is no any provision in the income tax Act 1961 to file GST return and also no any office is established in income tax office Mumbai to file GST return. Main question is that whether TCS should be collected with GST or not. My opinion is in support of that. GST return and TDS/TCS return is different. About rates of GST, I have searched in Google.