Refunds of 4% Additional Duty: claimants must submit prescribed documents and CA certifications to establish VAT/CST correlation and avoid delays. Refunds of 4% Additional Duty are subject to Notification No.102/2007 and Board circulars; claims must be filed within one year of actual payment and ordinarily only one claim per bill of entry is permitted. Claimants must submit importer copy of Bills of Entry with TR-6 challans, sales invoices (hard copy or electronic with declaration), and original documentary proof of VAT/CST payment or CA-certified copies. A certificate from the Statutory Auditor/Chartered Accountant who certifies the claimant's accounts is required to correlate imports, sales and VAT/CST payments and to state that the incidence of 4% duty was not passed on, with working sheets and explanations to rule out unjust enrichment.