Estoppel by conduct was applied where the petitioner voluntarily...

Estoppel by conduct was applied where the petitioner voluntarily paid differential customs duty during a DRI investigation, sought closure and remained silent thereafter; the Court held this conduct barred a subsequent refund claim. The Court held Notification No.25/2019-Customs and the Finance Act amendment operate prospectively and do not alter duty lawfully incurred on 2014-2017 imports. Because payment was voluntary and investigation closure was accepted, no show cause notice was required, and the refund failed for lack of evidence negating unjust enrichment.