You cannot use an import permit with a "Z01" approval code to clear your import shipment that is covered under an Import Certificate. If the permit is unutilised, you have to cancel the permit and obtain a new permit. In the new permit application, please declare: (a) the Import Certificate and Delivery Verification (ICDV) reference number in the format "ICDV/XXX/XXXX" in the "Competent Authority/Singapore Customs (CA/SC) Product Code" field, and (b) the import quantity in the "CA/SC Quantity" field. A correctly declared ICDV import permit will show an "A01" approval code.