Letter of Undertaking for exports permits integrated-tax-free shipments; non-payment of due tax and interest leads to withdrawal until restored. All registered persons may furnish a Letter of Undertaking in place of a bond to export without payment of integrated tax, except those prosecuted for offences where the tax evaded exceeds a statutory threshold; the LUT must be furnished in duplicate on letterhead in the annexure to FORM GST RFD-11 and executed by specified senior officials or authorised persons. Failure to pay tax with interest within the prescribed period leads to withdrawal of the LUT facility, which is restored upon payment; the provisions apply mutatis mutandis to zero-rated supplies to SEZ developers and units.