The Shippers's Letter of instruction (SLI) is a document used to provide all necessary information about an international shipment to a freight forwarder or carrier. The shipper is responsible for filling out the SLI, which includes details such as the goods being shipped, origin/destination, mode of transport, and special handling requirements. It helps ensure proper handling of the cargo and all necessary documents are obtained.

The SLI may be required by law for certain exports, such as from the United States, or used voluntarily by the shipper to clearly communicate their requirements and ensure proper handling of the cargo.

The SLI is filled out by the exporter/shipper, including details about the shipment, and then provided to the freight forwarder/carrier to ensure proper handling of the shipment and obtaining of necessary documents. The SLI serves as a single source of information for the shipment and includes information about goods, origin/destination, mode of transport, and special requirements.