Shipper’s Letter of Instructions is a document which provides shipping instructions to the shipper’s freight forwarder to ensure accurate and correct movement of their products across borders. Often this document will include billing terms regarding the freight and other charges as well as documentation preparation instructions in cases where the shipper is not providing those documents. In some cases product distribution instructions are also included. The SLI should provide the basic data elements that allow a forwarder to process the export with AES.