Non-realisation of export proceeds: repay refunded IGST with interest; recovery follows tax recovery provisions unless RBI waives requirement. Where refund of unutilised input tax credit or integrated tax on exported goods has been paid but export sale proceeds are not realised within the FEMA period (including extensions), the recipient must deposit, within thirty days of expiry, the portion of the refund corresponding to non realisation with interest; otherwise the amount is recoverable as an erroneous refund under the Act with interest under section 50. If proceeds are realised later and evidence is produced within three months, the recovered amount shall be refunded to the extent of realisation, provided realisation fell within any RBI extended period.