--- title: "Shipper’s letter of instruction (sli)" description: "A document containing instructions given by the shipper or the shipper’s agent for preparing documents and forwarding (aircargo)." url: "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli" date: "2026-05-23T14:48:57+00:00" language: "en-GB" --- ![Ocean Cargo](https://oceancargo.co.uk/images/GenPics/OCs-Customs-Brokerage.webp) # Shipper's Letter of Instruction (SLI): The Definitive Guide for UK Importers and Exporters ## Understanding the Shipper’s Letter of Instruction In the world of international trade, clarity prevents delay. A Shipper’s Letter of Instruction (SLI) is a formal letter from an exporter to a freight forwarder. It contains the exact details of a shipment and authorises the forwarder to act as the exporter’s agent for customs and transport purposes. While it is a standard requirement for [air freight](https://oceancargo.co.uk/services/air-freight/), its use in sea and road transport is equally vital for maintaining a clean audit trail. At Ocean Cargo, we treat the SLI as a contract of instruction. It tells us who to bill, where to deliver, and how to classify your goods. Without this document, forwarders must rely on verbal cues or fragmented emails, which increases the risk of documentation errors. By providing a signed SLI, you grant your forwarder a specific power of attorney to sign documents, such as the Air Waybill (AWB), on your behalf. Accurate instructions are the first line of defence against customs queries. We work closely with the [British International Freight Association (BIFA)](https://www.bifa.org) to ensure our processes meet the highest industry standards. As BIFA members, we use the SLI to uphold professional ethics and regulatory compliance across every lane. ## The Strategic Importance of the SLI Many businesses view the SLI as a burden of paperwork. However, it is a strategic tool that protects your financial and legal interests. When you fill out this form, you are defining the rules of engagement for your logistics partner. ### Legal Protection and Agency The SLI establishes the "Agency" relationship. Under UK law, a freight forwarder acts as either a principal or an agent. Most often, the forwarder acts as your agent for export declarations. The SLI provides the written proof that you have authorised us to submit data to HM Revenue & Customs (HMRC). This is vital for your records during a post-clearance audit. ### Precision in Customs Declarations HMRC uses the Customs Declaration Service (CDS) to process imports and exports. This system requires granular data. The SLI provides the "Source of Truth" for this data. If the information on your SLI differs from your Commercial Invoice, it creates a red flag. We use the SLI to cross-reference your [customs clearance](https://oceancargo.co.uk/services/customs-clearance/) details, ensuring that the HS codes and values reported to the government are correct. ### Cost Control and Avoidance of Fees Logistics costs can spiral if documentation is incorrect. If we book a flight based on incorrect weights provided over the phone, the airline may charge a "dead freight" fee if the actual cargo is lighter, or they may bump the cargo if it is heavier. A written SLI forces a check of the physical data before the booking is finalised. This accuracy keeps your [sea freight](https://oceancargo.co.uk/services/sea-freight/) and air freight costs predictable. ## Critical Data Components of a Professional SLI A high-quality SLI leaves no room for interpretation. Each field on the form serves a specific purpose in the transit chain. To ensure your cargo moves without friction, you must provide the following details. ### Full Shipper and Consignee Details You must provide the full legal company name, registered address, and contact details for both the shipper (seller) and the consignee (buyer). Do not use abbreviations. Include the EORI (Economic Operators Registration and Identification) number. This is a mandatory ID for any business moving goods into or out of the UK. If you are shipping to the United States, you will also need to provide the consignee's IRS number (EIN) to facilitate [customs brokerage in the USA](https://oceancargo.co.uk/countries/usa/customs-brokerage-usa). ### Accurate Commodity Classification (HS Codes) The Harmonised System (HS) code is an eight or ten-digit number that tells customs exactly what your goods are. It determines the duty rates and whether you need an export licence. You should use the [UK Government’s Trade Tariff tool](https://www.gov.uk/trade-tariff) to find the correct code for your products. Providing an incorrect code can lead to overpayment of taxes or, worse, legal penalties for misdeclaration. Whether you are shipping [industrial tools](https://oceancargo.co.uk/project-cargo/shipping-industrial-tools) or complex chemicals, the code must be precise. ### Weights, Dimensions, and Packaging Carriers charge based on the "Chargeable Weight." This is the higher of the actual gross weight or the volumetric weight. You must provide: - **Gross Weight:** The total weight of the goods, including all pallets, crates, and wrapping. - **Net Weight:** The weight of the goods alone. - **Dimensions:** The length, width, and height of each individual piece. - **Number of Pieces:** The total count of cartons or pallets. For sea freight, you must also provide the Verified Gross Mass ([vgm](https://oceancargo.co.uk/blog/vgm-a-comprehensive-guide-to-verified-gross-mass "vgm")). Under the SOLAS (Safety of Life at Sea) regulations, shippers must provide the verified weight of a container to the carrier before it can be loaded onto a vessel. This prevents accidents caused by uneven or excessive loading. ## Incoterms 2020: Defining Risk and Cost Transfer The SLI must state the agreed Incoterms. These rules define where the seller's responsibility ends and the buyer's begins. Choosing the wrong term on your SLI can result in you paying for freight or insurance that your customer should have covered. ### Common Terms for UK Exporters - **EXW (Ex Works):** The buyer assumes all costs and risks from the moment the goods leave your factory door. In this case, the SLI tells Ocean Cargo to bill the consignee for all charges. - **FCA (Free Carrier):** You deliver the goods to a named place (like our warehouse). You handle the export clearance. This is often preferable to EXW because you retain control over the export declaration, which is vital for VAT zero-rating. - **DAP (Delivered at Place):** You pay for the transport to the buyer's door, but the buyer pays the import duties and taxes. - **DDP (Delivered Duty Paid):** You cover all costs, including import taxes in the destination country. This requires a robust partner for [customs clearance](https://oceancargo.co.uk/services/customs-clearance/) to manage the foreign tax requirements. Using the correct Incoterm ensures that Ocean Cargo knows exactly who to invoice and who is responsible for the cargo insurance at each stage of the journey. ## Documentation Requirements by Mode The SLI acts as a cover sheet for your entire document pack. Depending on how you ship, you will need to attach different certificates. ### Air Freight Specifics For [air freight](https://oceancargo.co.uk/services/air-freight/), the SLI allows us to issue the House Air Waybill (HAWB). If the goods are hazardous, you must also provide a Shipper’s Declaration for [Dangerous Goods](https://oceancargo.co.uk/services/specialised-services/specialised-services-dangerous-goods "Dangerous Goods") (DGD). This document must match the SLI exactly regarding the UN number, proper shipping name, and packing group. ### Sea Freight and the Bill of Lading In [sea freight](https://oceancargo.co.uk/services/sea-freight/), the SLI provides the data for the Bill of Lading (BOL). The BOL is a document of title; whoever holds the original "negotiable" BOL owns the goods. Your SLI should specify if you want a "Sea Waybill" (which allows for quick release) or an "Original Bill of Lading" (which requires physical documents to be sent to the buyer via courier). ### Road Freight and CMR When using [road freight](https://oceancargo.co.uk/services/road-freight/) to Europe, the SLI helps us prepare the CMR note. This is the standard contract for international road transport. It records any damage to the packaging at the point of collection, which is vital for claims handling. ## Expert Checklist: Insider Tips for a Perfect SLI To help you avoid the most common pitfalls, our operations team has compiled this "insider" checklist to help you complete your instructions. - **Verify the EORI:** Always check that the consignee's EORI is active before shipping. An inactive EORI will cause an immediate customs hold at the destination. - **Match the Invoice:** Ensure the "Total Value" and "Currency" on the SLI match the Commercial Invoice exactly. Discrepancies lead to manual inspections. - **Declare Hazards Early:** Even if a product is "Not Restricted," if it contains a battery or a magnet, state this on the SLI. This allows us to provide the MSDS (Material Safety Data Sheet) to the carrier and prevent the cargo from being rejected at the terminal. - **Be specific about handling:** If a crate cannot be stacked, do not just tell the driver. Write "DO NOT STACK" in large letters on the SLI. This gives us the legal grounds to hold a carrier liable if they ignore the instruction. - **Check Wood Packaging:** If you are shipping in wooden crates, ensure they are ISPM15 compliant. State this on the SLI to avoid the goods being returned or destroyed by port health authorities. ## Risk Management and Cargo Insurance Standard carrier liability is limited. Under BIFA conditions or international conventions such as the Hague-Visby Rules (for sea) or the Montreal Convention (for air), the carrier pays a set amount per kilogram if goods are lost or damaged. This amount is often far below the actual value of your cargo. The SLI includes a section where you can "Declare Value for Carriage" or "Declare Value for Insurance." If you want Ocean Cargo to arrange comprehensive "All Risks" insurance, you must clearly state the value and the currency on the SLI. This ensures that your financial interest is protected from the moment the goods leave your warehouse until they reach the final destination. This is especially critical for high-value shipments, such as [aircraft parts](https://oceancargo.co.uk/project-cargo/shipping-aircraft-parts) or [high-tech equipment](https://oceancargo.co.uk/project-cargo/shipping-high-tech-comms-equipment). ## How Ocean Cargo Processes Your Instructions When you submit an SLI to Ocean Cargo, it triggers a sequence of professional actions designed to optimise your supply chain. 1. **Technical Review:** A logistics specialist reviews the data for completeness. We check HS codes and documentation against destination requirements. 2. **Carrier Selection:** We match your cargo to the best carrier. If you ship to a landlocked country, we might coordinate [road freight](https://oceancargo.co.uk/services/road-freight/) from a major port. 3. **Customs Entry:** Our clearance team uses the SLI to build the export declaration in the CDS. We ensure that any required licences, such as those for [military equipment](https://oceancargo.co.uk/project-cargo/shipping-military-equipment), are attached. 4. **Real-Time Updates:** We use the SLI's contact details to keep all parties informed. You receive notifications at every milestone. 5. **Audit Trail:** We archive the SLI alongside the final shipping documents. This provides you with a robust record for your VAT and tax compliance. Our hands-on approach ensures that we catch errors before they become costs. We don't just move boxes; we manage the data that enables global trade. #### Is the Shipper's Letter of Instruction a legal contract? The SLI is a set of instructions that forms part of the broader service agreement. While the overarching contract is governed by our standard trading conditions, the SLI provides the specific, shipment-level legal mandate for us to act as your agent. It is a legally binding set of instructions that dictates how we handle your cargo and documentation. #### Why do I need an SLI for air freight but not always for sea freight? Air freight moves much faster than other modes. Airlines require the Air Waybill to be finalised almost immediately upon the cargo's arrival at the terminal. The SLI ensures the forwarder has all the data to meet these tight windows. For [sea freight](https://oceancargo.co.uk/services/sea-freight/), the timelines are longer, but using an SLI is still "best practice" to ensure the Bill of Lading is accurate and to prevent costly manifest corrections later. #### What is a "Neutral" SLI? A neutral SLI is a form that does not carry the branding of a specific freight forwarder. It allows a shipper to use the same format for all their logistics providers. However, using an Ocean Cargo-branded SLI is often better, as it is tailored to our specific operational systems and ensures no critical data fields are missed. #### Can I use one SLI for multiple shipments? We recommend a fresh SLI for every shipment. Even if the customer and the product are the same, the weights, values, and container numbers will differ. Using a unique SLI for each "job" ensures a clean audit trail and prevents data from one shipment from being incorrectly applied to another. This is vital for maintaining [customs compliance](https://oceancargo.co.uk/services/customs-compliance). #### What happens if the information on the SLI is wrong? Errors on the SLI can lead to customs holds, fines, and additional transport costs. If the weight is wrong, the carrier may recharge the freight at a higher rate. If the HS code is wrong, the buyer may pay too much duty or the goods could be seized. If you discover an error, you must contact your Ocean Cargo representative immediately to issue a correction before the export declaration is finalised. #### Does the SLI include the commercial invoice? The SLI is a separate document, but it should always be accompanied by the Commercial Invoice and Packing List. The SLI tells the forwarder what to do with those documents. Think of the invoice as the "what" and the SLI as the "how." For specialised moves such as project logistics, you may need even more supporting documentation. ### Ready to simplify your global logistics? Get advice and a quote for your next shipment. Contact the Ocean Cargo team to start shipping. [Freight Quote](https://oceancargo.co.uk/contact-us) ## Your Strategic Logistics Partner Ocean Cargo is more than a freight forwarding company; we are your strategic logistics partner. Our focus lies in simplifying complex supply chains and turning logistical challenges into operational gains. We build strong relationships, apply relevant technologies, and offer a hands-on, consultative approach to every project. Our conduct is governed by integrity and a focus on execution. **BIFA Member No. 4489** As accredited members of the [British International Freight Association](https://www.bifa.org), Cargo Dynamic Ltd. operates to recognised industry standards for professionalism, compliance, and service delivery. We apply the BIFA Standard Trading Conditions to all business undertaken. ![BIFA Member No 4489](https://oceancargo.co.uk/images/BIFA_Member_No4489.jpg) ## Schema ```json { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://oceancargo.co.uk" }, { "@type": "ListItem", "position": 2, "name": "Shipping Terms", "item": "https://oceancargo.co.uk/shipping-terms" }, { "@type": "ListItem", "position": 3, "name": "Shipper’s letter of instruction (sli)", "item": "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli" } ] } ``` ```json { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Is the Shipper's Letter of Instruction a legal contract?", "acceptedAnswer": { "@type": "Answer", "text": "The SLI is a set of instructions that forms part of the broader service agreement. While the overarching contract is governed by our standard trading conditions, the SLI provides the specific, shipment-level legal mandate for us to act as your agent. It is a legally binding set of instructions that dictates how we handle your cargo and documentation." } }, { "@type": "Question", "name": "Why do I need an SLI for air freight but not always for sea freight?", "acceptedAnswer": { "@type": "Answer", "text": "Air freight moves much faster than other modes. Airlines require the Air Waybill to be finalised almost immediately upon the cargo's arrival at the terminal. The SLI ensures the forwarder has all the data to meet these tight windows. For sea freight, the timelines are longer, but using an SLI is still "best practice" to ensure the Bill of Lading is accurate and to prevent costly manifest corrections later." } }, { "@type": "Question", "name": "What is a "Neutral" SLI?", "acceptedAnswer": { "@type": "Answer", "text": "A neutral SLI is a form that does not carry the branding of a specific freight forwarder. It allows a shipper to use the same format for all their logistics providers. However, using an Ocean Cargo-branded SLI is often better, as it is tailored to our specific operational systems and ensures no critical data fields are missed." } }, { "@type": "Question", "name": "Can I use one SLI for multiple shipments?", "acceptedAnswer": { "@type": "Answer", "text": "We recommend a fresh SLI for every shipment. Even if the customer and the product are the same, the weights, values, and container numbers will differ. Using a unique SLI for each "job" ensures a clean audit trail and prevents data from one shipment from being incorrectly applied to another. This is vital for maintaining customs compliance." } }, { "@type": "Question", "name": "What happens if the information on the SLI is wrong?", "acceptedAnswer": { "@type": "Answer", "text": "Errors on the SLI can lead to customs holds, fines, and additional transport costs. If the weight is wrong, the carrier may recharge the freight at a higher rate. If the HS code is wrong, the buyer may pay too much duty or the goods could be seized. If you discover an error, you must contact your Ocean Cargo representative immediately to issue a correction before the export declaration is finalised." } }, { "@type": "Question", "name": "Does the SLI include the commercial invoice?", "acceptedAnswer": { "@type": "Answer", "text": "The SLI is a separate document, but it should always be accompanied by the Commercial Invoice and Packing List. The SLI tells the forwarder what to do with those documents. Think of the invoice as the "what" and the SLI as the "how." For specialised moves such as project logistics, you may need even more supporting documentation." } } ] } ``` ```json { "@context": "https://schema.org", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli" }, "headline": "Shipper’s letter of instruction (sli)", "description": "A document containing instructions given by the shipper or the shipper’s agent for preparing documents and forwarding (aircargo).", "image": { "@type": "ImageObject", "url": "https://oceancargo.co.uk/images/GenPics/sea-freight3.webp" }, "publisher": { "@type": "Organization", "name": "Ocean Cargo", "logo": { "@type": "ImageObject", "url": "https://oceancargo.co.uk/images/300_ocean-logo.png" } }, "author": { "@type": "Person", "name": "Ocean Cargo", "url": "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli" }, "datePublished": "2025-09-04T02:54:38+00:00", "dateCreated": "2025-06-30T11:22:31+00:00", "dateModified": "2026-01-24T11:23:14+00:00" } ``` ```json { "@context": "https://schema.org", "@type": [ "LocalBusiness" ], "@id": "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli#localbusiness3", "name": "Ocean Cargo", "image": "https://oceancargo.co.uk/images/300_ocean-logo.png", "url": "https://oceancargo.co.uk/shipping-terms/shippers-letter-of-instruction-sli", "address": { "@type": "PostalAddress", "addressCountry": "UK", "addressLocality": "Oldham", "postalCode": "OL8 2PF" }, "openingHoursSpecification": { "@type": "OpeningHoursSpecification", "dayOfWeek": [ "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" ], "opens": "00:00", "closes": "23:59" }, "aggregateRating": { "@type": "AggregateRating", "ratingValue": "4.8", "reviewCount": "500", "worstRating": 0, "bestRating": 5 } } ```