GST LUT (Letter of Undertaking) filing refers to a process under the Goods and Services Tax (GST) regime in India. The Letter of Undertaking (LUT) is a document that exporters use to claim exemption from the requirement of paying Integrated Goods and Services Tax (IGST) on export supplies.

Here’s a brief description of GST LUT filing:

1. **Purpose**: The primary purpose of filing a GST LUT is to facilitate exports without payment of IGST. Under GST, exports are considered as zero-rated supplies, meaning that they are not subject to tax. Exporters can claim refunds of taxes paid on inputs or input services used in manufacturing the exported goods or services.

2. **Eligibility**: Registered taxpayers who export goods or services without payment of IGST can file a GST LUT to avail of the zero-rated supply benefit.

3. **Procedure**: The procedure for filing a GST LUT involves submitting the LUT form, typically Form GST RFD-11, on the GST portal. The form requires details such as the name and address of the exporter, GSTIN, financial year, details of exports, declaration of compliance, etc.

4. **Validity**: Once filed and accepted by the GST authorities, the GST LUT is valid for a specific period, usually for the financial year for which it is filed. Exporters need to renew the LUT annually.

5. **Non-compliance**: If an exporter fails to comply with the conditions specified in the GST LUT or if exports are not made within the prescribed time frame, the exporter may be required to pay IGST on exports and might lose the privilege of availing zero-rated supplies.

6. **Documentation**: Exporters must maintain proper documentation and records of exports, including invoices, shipping bills, export orders, and other relevant documents, to support their claim for zero-rated supplies and facilitate the processing of refunds.

Overall, GST LUT filing streamlines the export process and provides exporters with the necessary documentation to claim exemptions from paying IGST on exports. It is essential for exporters to understand the requirements and comply with the regulations to benefit from the zero-rated supply provisions under GST.