The central issue is whether the bar of unjust enrichment under...

The central issue is whether the bar of unjust enrichment under show cause proceedings prevents refund of duty on cash and quantity discounts; the tribunal's earlier orders became final and therefore bar recovery, entitling the taxpayer to refund. The Commissioner (Appeals) erred in rejecting chartered accountant certificates and dealer affidavits showing duty incidence was not passed on; absence of contrary evidence meant those certificates were admissible and probative, so refunds must be allowed. Consequently, amounts challenged as erroneously refunded cannot be recovered where final tribunal decisions and acceptable evidence establish no unjust enrichment.