What Is a Shipper’s Letter of Instruction (SLI)?

A Shipper’s Letter of Instruction (SLI) is an important document in international shipping. It provides a freight forwarder with the information and instructions needed to process an export shipment correctly.

In air freight, an SLI helps coordinate shipment preparation, export documentation, and customs procedures. It also helps reduce errors by clarifying the shipper’s requirements before the cargo leaves the country.

Understanding how an SLI works can help exporters improve shipping efficiency and avoid unnecessary delays.

What Is a Shipper’s Letter of Instruction?

A Shipper’s Letter of Instruction is a document prepared by an exporter or shipper. It tells the freight forwarder how to handle and process a shipment.

The document typically includes shipment details, cargo information, export instructions, and authorization for specific services.

An SLI may also provide instructions for preparing export declarations or an air waybill, depending on the shipment and the services requested.

Although an SLI is commonly used in international freight forwarding, it is not the same as an air waybill or a customs declaration.

Why Is an SLI Important in Air Freight?

Air freight shipments often involve multiple parties, including exporters, freight forwarders, airlines, customs authorities, and overseas consignees.

Clear instructions help these parties coordinate their responsibilities.

An SLI offers several benefits:

• Improves communication: It explains the shipper’s requirements clearly.
• Reduces documentation errors: It helps the forwarder prepare shipping documents using the supplied information.
• Supports export processing: It provides relevant details for customs procedures when applicable.
• Clarifies responsibilities: It records the services and instructions requested by the shipper.
• Helps prevent delays: Accurate information reduces the need for repeated corrections.

An SLI does not guarantee customs clearance, but it can help make the export process more organized.

What Information Does an SLI Contain?

The information required depends on the shipment, destination, and freight forwarder. A typical SLI may include the following details.

1. Shipper and Consignee Information

This section identifies the parties involved in the shipment.

It commonly includes:

• Shipper’s name and address.
• Consignee’s name and address.
• Contact details.
• Exporter or importer identification numbers, where required.

The information should match the relevant commercial and shipping documents.

2. Cargo Description

The cargo section describes the goods being shipped.

Typical details include:

• Product description.
• Number of packages.
• Gross weight.
• Dimensions.
• Packaging type.
• Commodity or HS code, when required.

Accurate cargo information helps the freight forwarder arrange the shipment appropriately.

3. Shipping Instructions

This section explains how the shipment should be handled.

Instructions may cover:

• Requested shipping method.
• Origin and destination airports.
• Preferred departure date.
• Delivery requirements.
• Special handling instructions.
• Insurance arrangements, if requested.

Any special requirements should be communicated before the cargo is accepted for transport.

4. Export Documentation Instructions

An SLI may authorize or instruct the freight forwarder to prepare certain export documents.

Depending on the arrangement, these may include:

• Air Waybill (AWB).
• Export customs declaration.
• Other shipment-related documents.

The shipper should review the information carefully and confirm that it is accurate before submission.

How Does the SLI Process Work?

The SLI process usually follows several steps.

1. The exporter prepares shipment details. The shipper gathers cargo information, consignee details, and export documentation.
2. The exporter completes the SLI. Instructions are provided to the selected freight forwarder.
3. The forwarder reviews the information. Missing details or inconsistencies may be clarified with the shipper.
4. Shipping documents are prepared. The forwarder uses the verified information to prepare the applicable documents.
5. The cargo is processed for export. The shipment proceeds through the required handling and customs procedures.
6. The cargo is handed over for air transportation. The airline or handling agent receives the shipment according to the applicable process.

The exact workflow varies by country, forwarder, and shipment type.

What Is the Difference Between an SLI and an Air Waybill?

An SLI and an Air Waybill serve different purposes in air freight.

Comparison	Shipper’s Letter of Instruction (SLI)	Air Waybill (AWB)
Main purpose	Provides instructions to the freight forwarder	Documents the air carriage of goods
Prepared by	Usually the exporter or shipper	Usually issued by the airline or its authorized agent
Primary function	Communicates shipment requirements	Records key details of the air transportation
Role in shipping	Guides shipment processing	Serves as the air transport document
Transport contract	Not itself the air carriage contract	Generally serves as evidence of the contract of carriage

The SLI helps the forwarder understand what the shipper needs. The AWB records the shipment details used for air transportation.

Common Mistakes When Completing an SLI

Incorrect instructions can cause documentation problems and shipment delays.

Exporters should avoid these common mistakes:

• Entering an incorrect consignee address.
• Providing an incomplete cargo description.
• Reporting inaccurate weight or dimensions.
• Using inconsistent information across documents.
• Omitting special handling instructions.
• Failing to identify applicable export requirements.
• Sending the SLI too late for the planned departure.

Reviewing the document before submission can help prevent these issues.

Best Practices for Preparing an SLI

Businesses can improve export operations by following a few practical steps.

Verify All Shipment Details

Check the shipper, consignee, cargo description, package count, weight, and dimensions.

Keep Documents Consistent

Ensure the information matches the commercial invoice, packing list, and other applicable documents.

Provide Instructions Early

Send the SLI to the freight forwarder as early as possible to allow time for review and correction.

Disclose Special Cargo Requirements

Inform the forwarder if the shipment contains dangerous goods, temperature-sensitive products, fragile items, or other cargo requiring special handling.

Work with an Experienced Freight Forwarder

A professional forwarder can explain the required information and identify potential documentation issues before shipment.

Frequently Asked Questions

1. Is a Shipper’s Letter of Instruction mandatory for every air freight shipment?

Not necessarily. Requirements vary by country, shipment type, and freight forwarder. The exporter should confirm whether an SLI is required for the specific shipment.

2. Who completes the SLI?

The exporter or shipper typically completes and provides the instructions. The freight forwarder may supply a template or assist with preparing the document.

3. Is an SLI the same as an Air Waybill?

No. An SLI provides instructions to the freight forwarder, while an AWB documents the air carriage of the goods.

4. Can an incorrect SLI delay a shipment?

Yes. Missing or inconsistent information may require corrections and can delay documentation, export processing, or cargo acceptance.

5. Does an SLI replace export customs documents?

No. An SLI does not replace a customs declaration or other documents required by the relevant authorities.

Conclusion

A Shipper’s Letter of Instruction (SLI) is a useful document for coordinating international air freight shipments. It helps exporters communicate their requirements, supports accurate documentation, and clarifies the instructions given to freight forwarders.

By providing complete information, checking document consistency, and submitting instructions early, businesses can reduce avoidable errors and improve the efficiency of their export operations.

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