Gst queries for b2b

I have some queries regarding GST. (Actually many :-) )I read somewhere that freight and packaging charges must also be added under taxable value before issuing invoice to retailer. Is it true? Actually the thing is that I am a B2B supplier and currently in our business we bear the transportation and packaging charges on behalf of our customers. What should I do then?Also I heard that I will have to issue an extra copy of invoice (instead of 2 currently) to the transporter. Also there is something called invoice reference number. I also heard that I can give this invoice reference number instead of issuing extra invoice. What is this invoice reference number? Do I need to mention this number on my each invoice? Please clarify.As I told you earlier I am wholesale cloth merchant. We mainly deal with cotton cloths. Before GST it was exempted from excise duty etc. Then what should I do with my existing stock. Many of my colleagues are saying that we need to pay return on closing tax at the rate of GST (1.e. 5%). This is biggest confusion prevailing in our community. Even many of CAs in my area aren't clear about it.Please respond quickly.Thanks in advance.

1. Transportaion, packing charges has to be included in the value of goods - composite supply, principal supply is supply of goods.

2. As per Law, you need to issue 3 copies of tax invoices - one for customer, one for you, one for the transporter. (Rule 48 of CGST Rules). 

3. Supply of textile material is taxable under GST. Applicable rate of tax has to be determined on case to case basis.