Export or supply to SEZ unit or developer of goods or services is inter-state trade or commerce :
Supply of goods or services or both –
(a) when the supplier is located in India and the place of supply is outside India
(b) to or by a Special Economic Zone developer or a Special Economic Zone unit; or
(c) in the taxable territory, not being an intra-State supply and not covered elsewhere in this section – – shall be treated to be a supply of goods or services or both in the course of inter-State trade or commerce – section 7(5) of IGST Act.
Thus, in case of export of goods or services, SGST cannot apply.