Refund of 4% Additional Duty requires specified documents, CA certification, single monthly claim, and non-passing declaration. Refunds of the 4% Additional Duty of Customs under Notification No. 102/2007 require submission of duplicate Bill of Entry, TR-6 challan, original sales invoices and VAT challans, a calculation worksheet (Annexure-A), self-declaration (Annexure-B), and a Chartered Accountant certificate (Annexure-D). Only one consolidated refund claim per importer per month is permitted. Originals of VAT challans and sales invoices will be returned after endorsement or settlement. Importers must declare non-passing of the duty incidence, payment of applicable sales tax/VAT/CST on resale, and proper accounting treatment; the CA must certify correlation and absence of unjust enrichment.