Unjust enrichment principle limits GST refunds, subject to specific exceptions like zero-rated supplies and unutilized input tax credit. The unjust enrichment principle applies to refunds generally, but does not bar refunds for zero-rated supplies and associated inputs, unutilized input tax credit from rate differentials, supplies not provided without invoicing, tax wrongfully collected and paid to government, instances where tax incidence was not passed on, and other classes as notified by the Government.