What is EDI 856? A Complete Guide to Advance Ship Notices

EDI 856, the Advance Ship Notice (ASN), is the document that tells your retail customer exactly what you shipped, how it's packed, and when it will arrive — before it gets there. If the EDI 850 is the order and the EDI 810 is the bill, the 856 is the bridge between them. It's how retailers prepare their receiving docks, update their inventory systems, and reconcile what was ordered against what actually showed up.

For most retailers, the ASN isn't optional. Walmart, Target, Amazon, Kroger, and Home Depot all require it, and they track your accuracy closely.

What an EDI 856 Contains

An ASN provides a detailed, hierarchical description of a shipment. It answers the questions a receiving dock needs answered before the truck arrives:

Shipment Level

• Ship date and estimated delivery date
• Carrier and tracking information (PRO number, BOL number, SCAC code)
• Ship-from and ship-to addresses
• Total weight and number of cartons

Order Level

• Purchase order number(s) — which POs this shipment fulfills
• Buyer and seller identifiers

Pack Level

• Carton-level detail — what's in each box
• SSCC-18 barcode — a unique serial shipping container code for every carton
• Pack size and carton dimensions

Item Level

• Product identifiers — UPC, GTIN, or buyer's item number
• Quantity shipped per item per carton
• Unit of measure
• Lot numbers or expiration dates (for food, pharma, and perishables)

This hierarchical structure — shipment → order → pack → item — is what makes the 856 more complex than most other EDI documents. It's not a flat list; it's a nested description of how physical goods are organized.

Why Retailers Require ASNs

Faster Receiving

Without an ASN, a warehouse receiving team has to open every carton, scan every item, and manually check it against the PO. With an ASN, they scan the SSCC-18 barcode on the outside of each carton and the system already knows what's inside. This can cut receiving time by 50% or more.

Inventory Accuracy

The ASN updates the retailer's inventory system before goods physically arrive. This means their website, store allocation system, and replenishment engine all reflect incoming stock — reducing stockouts and improving availability.

Three-Way Matching

Retailers reconcile three documents before paying a supplier: the PO (850), the ASN (856), and the invoice (810). If the ASN says you shipped 100 units but the PO was for 120, or the invoice is for 100 but the ASN says 90, the discrepancy gets flagged. Accurate ASNs mean faster payment.

Chargeback Prevention

Inaccurate or late ASNs are one of the most common causes of retailer chargebacks. Walmart charges for late ASNs, missing SSCC-18 barcodes, quantity mismatches, and incorrect carton counts. These chargebacks can range from hundreds to thousands of dollars per incident.

How EDI 856 Fits in the Order-to-Cash Flow

Here's where the ASN sits in the typical EDI workflow:

1. Retailer sends EDI 850 (Purchase Order) — "We want 500 units of Product A"
2. You send EDI 997 (Acknowledgment) — "Got it"
3. You send EDI 855 (PO Acknowledgment) — "We can fill 450 of the 500"
4. You pick, pack, and ship the order
5. You send EDI 856 (ASN) — "Here's exactly what's on the truck, how it's packed, and the tracking number"
6. Retailer receives and scans the shipment against the ASN
7. You send EDI 810 (Invoice) — "Here's the bill, matching what we shipped"
8. Retailer sends EDI 820 (Payment) — "Payment sent"

The ASN must be sent after the shipment leaves your facility but before it arrives at the retailer's dock. Most retailers require it within 24 hours of the ship date. Some want it within hours.

Common EDI 856 Challenges

SSCC-18 Barcode Generation

Every carton needs a unique SSCC-18 barcode that matches what's in the ASN. This requires:

• A GS1 Company Prefix (you register for this)
• Sequential serial number generation
• GS1-128 barcode printing on physical labels
• Exact match between the printed label and the EDI data

Getting this wrong is the single most common cause of ASN-related chargebacks. If the barcode on the box doesn't match the SSCC in the 856, the retailer's system can't reconcile the shipment.

Hierarchical Structure

Unlike a flat document like the 850, the 856 uses a hierarchical loop (HL segments) to describe the shipment → order → pack → item relationship. Getting the nesting wrong — putting items under the wrong carton, or missing a pack level — causes parsing failures and compliance issues.

Timing

The ASN has a narrow window. Send it too early (before you've actually shipped) and the data might not match reality. Send it too late (after the truck arrives) and it's useless — the retailer has already received blind. Automating ASN generation from your shipping or warehouse system is the most reliable approach.

Partial Shipments

When you can only fill part of a PO, the ASN must accurately reflect the partial quantities. This means adjusting item-level quantities, potentially sending multiple ASNs for the same PO, and making sure the invoice later matches what the ASN reported.

Multi-Stop Shipments

If one truck delivers to multiple retailer locations, each stop needs its own ASN (or a single ASN with clearly delineated ship-to addresses). Mixing up which items go to which location is a compliance failure.

Retailer-Specific Requirements

While the X12 856 standard provides the framework, each retailer has its own implementation guide with specific requirements:

Walmart:

• SSCC-18 required on every carton
• ASN must be sent within 24 hours of ship date
• Carton contents must match exactly — no "approximately 100 units"
• Department and category codes required

Target:

• ASN required for all vendor shipments
• DPCI (Department, Class, Item) codes used for product identification
• Specific pack-level requirements for different shipping methods (conveyable vs. non-conveyable)

Amazon Vendor Central:

• ASN required for PO fulfillment
• Specific requirements for case-pack vs. each-unit shipments
• Integration with Amazon's Vendor Central portal

Kroger:

• ASN required for DSD (Direct Store Delivery) and warehouse shipments
• Lot tracking and expiration date requirements for perishables

For retailer-specific details, see our guides: Walmart EDI Requirements | Target EDI Requirements

Best Practices

1. Automate ASN Generation

The most reliable ASNs are generated automatically from your warehouse management or shipping system at the moment goods leave the dock. Manual ASN creation is where errors happen.

2. Validate Before Sending

Check every ASN against the original PO before transmission:

• Do quantities match or are within accepted tolerance?
• Are all UPCs/GTINs valid?
• Does every carton have a unique SSCC-18?
• Is the ship-to address correct?

3. Match Your Labels to Your Data

Print SSCC-18 labels from the same data source that generates the ASN. Never create labels independently from the EDI document — that's how mismatches happen.

4. Send Promptly

Automate transmission so the ASN goes out immediately after shipment. Waiting until end-of-day or next-morning creates compliance risk.

5. Monitor and Respond to Errors

Set up alerts for ASN rejections, compliance warnings, and chargeback notices. When an ASN fails, fix the root cause — don't just correct the single document.

Simplifying ASN Management

The 856 is often the most complex EDI document suppliers deal with. The hierarchical structure, SSCC-18 requirements, and per-retailer variations make it a common pain point.

OrderSync automates ASN generation, SSCC-18 barcode creation, and retailer-specific formatting. When an order ships, the ASN is generated from your shipping data, validated against the original PO, and transmitted to the retailer — no manual intervention required.

Ready to see how EDI works? Try our free EDI Inspector to visualize what's inside an 856 document.

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Related Resources:

• The Essential Guide to EDI
• What is EDI 850? Purchase Orders
• What is EDI 810? Electronic Invoices
• Walmart EDI Requirements
• Target EDI Requirements
• Free EDI Inspector Tool