Commissioner of GST Policy Wing vide Circular no. 10/10/2017-GST: Dated 18 October 2017 clarified the following in relation to supply on approval basis.
1. Goods which are taken for supply on approval basis can be moved from the place of business of the registered supplier to another place outside the State on a delivery challan with E-way Bill (as applicable).
2. Person carrying the goods for such supply can carry the invoice book with him so that he can issue the invoice once the supply is fructified.
3. Where the supplier carries goods from one State to another and supplies them in a different State, it will be inter-state supply chargeable to IGST.
On reading the complete circular and deriving a holistic view it can also be deduced that there is no requirement to take a separate registration of Casual Taxable Person in case goods are moved for supply on approval basis. Please use this circular carefully as this has not been explicitly mentioned in circular anywhere.