Sending goods abroad for exhibition is not a supply and triggers invoicing and refund rules only on sale or expiry. Goods sent or taken out of India for exhibition or consignment for export promotion are not a supply under section 7 and thus not a zero rated supply under section 16 unless covered by Schedule I. Such movements are treated as sale on approval, require a delivery challan under rule 55, and records per the annexure. Tax invoices must be issued when goods are sold abroad within six months or on expiry of six months if not sold or returned. Refunds of input tax credit for zero rated supply are claimable only after issuance of the tax invoice and meeting eligibility under section 54(3) and rule 89(4).