GST registration requirement clarified for importers and exporters: PAN suffices where GSTIN is not required, facilitating customs clearance. Where persons are not liable to registration under the CGST regime-including those making supplies that are not taxable or wholly exempt-GSTIN is not mandatory for import/export and authorized PAN (as IEC) will suffice; customs clearance should not be held up and PAN should be quoted in bills of entry and shipping bills.