What a Shipper's Letter of Instruction Actually Is
A Shipper's Letter of Instruction is simply the document you give your freight forwarder to tell them how to move your goods. It's not a customs form. It's not a bill of lading. It's your side of the communication chain, and it's usually what the forwarder uses to draft the bill of lading on your behalf. Got that wrong on a recent shipment and spent six hours on hold with a carrier because the forwarder guessed at the freight class instead of reading your instructions. Learned that the hard way. Here's what a real one looks like in practice. The header has your company name, address, contact info, and the forwarder's details. Then there's a section for shipment reference numbers, booking confirmations, and any prior correspondence. The cargo details come next — commodity description, HS code if you know it, number of packages, gross weight, dimensions, and whether the freight is hazardous or requires special handling. After that you list the shipping terms: Incoterms, origin port, destination port, and any intermediate stops. Then there's the delivery instructions — who's receiving the goods, where they should go, and what contact info the carrier needs at the destination. Finally, you note who pays for what: freight charges, customs fees, insurance, terminal handling. That's the backbone of it. One thing most people miss is that the commodity description needs to match exactly what's on the commercial invoice and packing list. I once sent an SLI that said "machine parts" while the invoice listed "hydraulic valve assemblies." Customs flagged it. The forwarder had to file a correction, the shipment sat for three days, and we ate demurrage charges because the container was sitting at the terminal waiting on paperwork that should have been consistent from the start.
How to Fill One Out Without Causing Problems
Start with the booking confirmation. If the forwarder gave you a booking number, put it at the top. Everything below that flows from it. Next, double-check the HS code against the product you're actually shipping. Don't copy-paste from a previous shipment unless you're certain the goods are identical. I've seen people use a legacy HS code from two years ago for a completely different product and end up with the shipment held at border inspection because the classification didn't match what the importer declared. The weight and dimension section is where things get real. If you're shipping palletized cargo, measure the pallet as a single unit including the base and overhang, not each individual box. If you're shipping loose cartons, list each carton's dimensions and the total volume. Forwarders use this to calculate chargeable weight, and getting it wrong means you're either overpaying or the carrier reweighs everything at the terminal and bills you the difference. Last month I had a shipment where the forwarder's system calculated freight based on our stated weight, the truck driver weighed it at the depot, and it came out 400 kilograms heavier than what we declared. The carrier issued a surcharge that ran over four hundred dollars because someone measured the cartons without the pallet base. On the Incoterms line, be specific. "FOB" means something different depending on whether you're using Incoterms 2010, 2014, or 2020. Write "FOB Shanghai, Incoterms 2020" and you've eliminated an entire category of confusion. Same with the delivery terms — if the consignee needs the goods delivered to a warehouse rather than the port, say so explicitly with the full address and contact number. I learned that the hard way when a forwarder delivered a container to the port terminal because the SLI only said "deliver to consignee" and the consignee's warehouse was twelve miles inland. The container sat at the port generating storage fees while we rearranged everything.
Common Pitfalls and What to Do About Them
The biggest issue I see is inconsistency between documents. The SLI, the commercial invoice, the packing list, and the bill of lading all need to agree on the commodity description, weight, and quantity. When they don't, you get holds, inspections, and delays. There's no automation that catches this — it's entirely on you to verify. My workaround is a simple spreadsheet where I paste the key data points from each document side by side and scan for mismatches before sending anything out. It takes about five minutes and has saved me from more customs headaches than I can count. Another thing: don't assume your forwarder knows your product. I worked with a forwarder who classified a shipment of laboratory equipment as general cargo because the SLI didn't specify the handling requirements. The equipment needed climate-controlled storage during transit and at the destination. It wasn't in the SLI, the forwarder didn't ask, and the cargo arrived degraded. The fix would have been a single sentence in the special instructions section noting temperature requirements and the acceptable range. If your shipment involves dangerous goods, the SLI is not enough. You need a proper declaration, MSDS documentation, and the forwarder needs to confirm they can handle that classification. A lot of people treat the SLI as the complete instruction package for hazardous materials. It's not. It's just the cover sheet. The actual DG paperwork is separate and it needs to accompany the SLI, not replace it.
Get the Full Details
Where to Get a Template
Most freight forwarders provide their own SLI form as part of the onboarding process. If you have a preferred forwarder, ask them for theirs. Using their template means less back-and-forth because their system is already built to read their format. If you don't have a forwarder yet or you ship through multiple ones, you can find standard templates through industry associations like the National Customs Brokers & Forwarders Association of America, or through customs broker forums where people share working versions. Just make sure whatever template you use includes fields for Incoterms, commodity description, weight, dimensions, and special instructions. Anything missing from that list is something you'll be filling in later and potentially getting wrong under time pressure.
