as per proviso to sec. 13 of IGST Act, 2017 if goods are imported in india for repair and reexport afer repair without use other than use that is require for repair work, place of supply of service will be outside of india and no IGST liab. will arise.
Proviso of section 13 of igst act is only for determination of place of supply... In this place of supply is outside country hence this is export of service... Hence charge igst and later he will get refunded.. If u have obtained LUT then no need to charge igst