A Letter of Undertaking (LUT) is a document that exporters can file to export goods or services without having to pay taxes. Brief on refund of IGST paid on Exports; Steps for claiming refund of IGST paid on Exports; When to file form RFD-01 / RFD-01A (for tax refund in. Exporters can now file Letter of Undertaking(LUT) online on GST portal before exporting Goods/ services without payment of IGST. LUT in GST: GST Letter of Undertaking · Export under Bond/LUT without payment of IGST in which case the exporter can claim refund of the. GST LUT or Letter of Undertaking can be filed by exporters using Form GST RFD 11 to enable exports from India without making IGST payment.