How to File a Shipper's Letter of Instruction

A Shipper's Letter of Instruction is the document that tells your freight forwarder what to do with your cargo. It's also one of the most common places shipments go wrong — not because the form is hard, but because something was vague.

What an SLI is

The SLI is a written instruction set from a shipper to their freight forwarder, authorizing them to prepare the export documentation, book the carrier, and handle customs paperwork on the shipper's behalf. It's not a legally required form the way a Commercial Invoice or Packing List is — but it's a near-universal practical requirement when you're using a forwarder.

Think of it as the briefing document. Everything that happens after the cargo leaves your dock flows from what's on the SLI. If the SLI says one thing and the Bill of Lading needs to say something else, the BL is what shows up — and amending it after the fact is expensive.

The information it captures

A complete SLI gives the forwarder everything they need to:

• Book the right carrier and routing
• Prepare the Bill of Lading correctly
• File the Electronic Export Information (EEI) with U.S. Customs for U.S. exports over $2,500
• Coordinate inland trucking, drayage, or rail
• Handle any letter of credit, certificate of origin, or special documentation requirements
• Confirm compliance requirements (ITAR, dual-use, sanctions screening)

At minimum you'll see:

• Parties — Shipper, Consignee, Notify Party details, matched to the commercial invoice exactly
• Cargo — description and Schedule B or HTS classification, quantities, weights, volumes, package types
• Routing — origin and destination ports, intended carrier preferences
• Terms — Incoterms and payment terms
• B/L preferences — original vs telex release, freight terms, freight amount visibility, special instructions

Common ways shippers get it wrong

After watching customers fill these out for years, a few patterns come up:

Vague commodity descriptions. "Industrial parts" isn't a description — it's a punt. The same goes for "miscellaneous goods" or "various items." Customs at destination needs to know what's actually in the container. Specifics like "stainless steel industrial pump replacement parts" prevent delays.

Mismatched party details. The Shipper field on the SLI must match the commercial invoice and certificate of origin exactly. "ACME Corp" vs. "Acme Corporation" vs. "ACME" can all trip up document review at destination. Pick one form and use it everywhere.

Missing Tax IDs. For some destinations, the consignee and notify party need a Tax ID number on the Bill of Lading or the cargo won't release. Brazil, India, and the EU are common offenders. Better to capture this on the SLI than to scramble for it after the cargo's on the water.

Multi-package containers entered as one line. A container holding 20 rolls of fabric AND 20 bags of pellets isn't "40 pieces — mixed." It's 20 rolls and 20 bags, listed separately. Customs reporting accuracy requires the package breakdown.

Schedule B codes guessed wrong. Even one wrong digit can trigger penalties from Census Bureau. If you're not sure, mark it for verification — forwarders would rather double-check than file wrong.

The five sections of a Conveyco SLI

Our online SLI form is structured around five practical sections, in the order an actual shipment unfolds:

1. Parties (Shipper, Consignee, Notify Party) — who's involved, with structured address fields and "Same as Consignee" shortcuts for routine cases
2. Cargo Details (per container) — what's moving, including multi-package types per container when needed
3. Schedule B Classification — formal commodity codes with quantities, weights, and the second-unit-of-measure for codes that require it
4. Commercial Terms — Incoterms, payment, letter of credit details, related-party and routed-transaction disclosures
5. B/L Preferences and Compliance — how the Bill of Lading should read, export license info, ITAR status, intermediate consignee handling

Handling complex commodity profiles

Real shipments are rarely "one thing in one container." Common complexities:

• Multiple package types in a single container — list each on its own line
• Multiple commodities in a single container — file separate Schedule B classifications for each
• Quantity-of-measure complications — some Schedule B codes require two units (a primary unit like kilograms PLUS a secondary unit like dozens or pieces). The code itself dictates which units are required.
• Related-party transactions — if the buyer and seller are in the same corporate family, that's a required compliance disclosure
• Routed transactions — when the foreign buyer is arranging the international shipping, the export documentation responsibilities shift

After you submit — what happens

When Conveyco receives an SLI, here's the flow:

1. The documentation team reviews for completeness
2. Routing options are confirmed based on origin, destination, and timing
3. The carrier booking goes in (you'll get the booking confirmation)
4. As cargo is received, containers and seals are matched against the SLI
5. The Bill of Lading is drafted and circulated for review — we send it to you before it's released
6. Final documents are issued, customs filings completed, cargo released

If anything in the SLI was unclear, you'll hear from us before the booking goes in. We'd rather ask one extra question than amend documents later.

Submitting your SLI

The fastest way is our online SLI form — it validates as you go, pre-fills repeat shipments via the "Use as Template" feature, and integrates with our internal documentation system so nothing falls through the cracks.

Prefer paper? Download the fillable PDF template, fill it in, email it to docs@theconveyco.com.

Either way, attach your commercial invoice and packing list. Those two documents plus the SLI are everything we need to start.