IGST on imports applies to EOUs and Advance Authorisation consignments, with IGST refundable upon subsequent exports. MEIS and SEIS scrips may be used only for payment of Basic Customs Duty; they do not cover GST. Advance Authorisation imports are exempt only from Basic Customs Duty while IGST must be paid and is refundable on exports. SEZs are exempt from both Basic Customs Duty and IGST on imports; EOUs must pay IGST on imports but may claim ITC or refunds after exports. Exporters must update IEC with GSTIN and ensure PAN accuracy; GSTIN in shipping bills is mandatory for ITC/refund claims.