Unjust enrichment applies to refunds for imported inputs used captively; claimants must prove duty wasn't passed on. The unjust enrichment principle applies to refunds of duty paid on imported raw materials consumed captively; claimants must establish that the incidence of duty was not passed on, directly or indirectly, to any other person before a refund under the statutory refund provisions is permitted. Central Excise refund practice is to be aligned with this requirement and pending or decided cases should be reviewed accordingly.