Unjust enrichment: refund claims require detailed financial examination and a reasoned speaking order specifying relied records. Refund eligibility requires examination of audited balance sheets, related financial records and Chartered Accountant certificates to determine whether the applicant passed on the duty or interest; the Assistant/Deputy Commissioner must issue a speaking order specifying the material relied upon and explaining the conclusion on unjust enrichment, and routine sanctioning or crediting to the Consumer Welfare Fund without such inquiry does not satisfy the statutory requirement.