What is a Shipper's Letter of Instruction?

According to the definition of official sources, a Shipper’s Letter of Instruction or SLI is a ‘letter’ from the exporter instructing the freight forwarder on how and where to handle the export shipment. The exporter is granting permission to the forwarder to act as the authorized forwarding agent for U.S. export control and customs. By completing an SLI and sending it to the freight forwarder, you are establishing a best practice for your firm. You have a written record of who received the shipping documents, who to contact for questions, who to contact for proof of export, and who issued the export control documentation that supports the decision to send your products to your foreign customer.