CSD refund application requires GST refund form with supplier invoice details, bank particulars, attachments and quarterly filing. Refund applications by the Canteen Stores Department must be submitted on the prescribed refund form capturing GSTIN, applicant details, tax period, refund amount, detailed inward supply invoice and debit/credit note particulars, and bank account information for refund transfer. Applicants must attach relevant returns statements for the period and provide a verified declaration by an authorised representative that goods were received and no duplicate refund claims exist. Applications are to be filed quarterly and invoices must show both supplier and CSD GSTINs.