Walmart EDI Overview: What You Are Getting Into

Walmart processes over 1 million supplier shipments per week across its US stores, Sam's Club locations, and fulfillment centers. At that scale, every transaction must be electronically transmitted in the exact format specified — there is no manual exception handling, no phone calls to fix a missing segment, no informal workarounds. EDI compliance is the admission ticket to the relationship.

Walmart uses a direct AS2 EDI connection model — you connect directly to Walmart's EDI infrastructure rather than through an intermediary VAN. This means your setup must include a functioning AS2 connection to Walmart's endpoint before you can begin testing.

The Walmart EDI program is governed by Walmart's Supplier EDI Standards document, which suppliers access through the RetailLink portal. The standards specify exact segment requirements, mandatory vs. optional fields, and the chargeback schedule for non-compliance. Updated versions are typically published annually, and suppliers are expected to implement changes within 90 days of publication.

New Supplier Timeline Expectation

Most new Walmart suppliers should budget 8–12 weeks from item setup to first live shipment — including EDI setup, testing, and certification. With an EDI platform that has Walmart's profile pre-configured (like SignalEDI), the technical setup can be completed in days; the bottleneck is usually Walmart's testing queue. Do not schedule your first shipment date before completing certification.

Required Transaction Sets: 850, 855, 856, 810

Walmart requires a specific set of EDI transactions for the purchase order lifecycle. Each transaction has precise requirements in Walmart's implementation guide, and each has compliance windows after which chargebacks apply.

850 — Purchase Order

Walmart sends you an 850 purchase order when it wants to buy your products. The 850 is inbound to you. Your obligations:

You must be able to receive and parse 850s within 24 hours of transmission
You must send a 997/999 functional acknowledgment within 24 hours of receiving the 850
The 850 contains Walmart's department number (N1*BY loop), shipping window dates (DTM segments), and item identifiers (UPCs in PO1 loops as UP qualifier)
Walmart's POs include a PO Revision Number (REF*8L) — track this to avoid processing the same PO twice when revisions are sent

Walmart 850 Key Segments (Abbreviated)

BEG*00*SA*PO-WMT-20260414**20260414~   ← PO type SA=Stand Alone
REF*8L*1~                               ← PO Revision Number (1=original)
DTM*010*20260420~                       ← Earliest ship date
DTM*038*20260425~                       ← Latest ship date
DTM*001*20260430~                       ← Cancel date (ship BEFORE this)
N1*BY*WAL-MART STORES*92*0078742000992~ ← Buying party (Walmart)
N1*ST*WAL-MART #1234*92*0078742001234~  ← Ship-to store number
PO1*1*144*EA*8.50**UP*0012345678905~    ← UPC in PO1 = GS1 GTIN-12
  PID*F****WIDGET PRODUCT 12CT~          ← Item description

855 — Purchase Order Acknowledgment

The 855 (Purchase Order Acknowledgment) is your response to Walmart's 850. You must send an 855 for every 850 received. Walmart uses the 855 to confirm what you are actually going to ship — particularly important for partial shipments.

ACK01 Code	Meaning	When to Use
AC	Item Accepted	Full quantity accepted; will ship as ordered
IA	Item Accepted, Changed Quantity	Partial acceptance — shipping less than ordered quantity
IB	Item Backordered	Item on backorder; provide expected ship date
IC	Item Accepted, Price Changed	Accepting item but invoicing at different price
ID	Item Deleted	Canceling this line item entirely
IP	Item in Process	Received, pending warehouse confirmation

856 — Advance Ship Notice (ASN)

The 856 ASN is the most compliance-sensitive transaction in the Walmart relationship. It must be sent within a specific window after shipment and must match the physical shipment exactly — quantity, UPC, packaging hierarchy, and pallet/carton label information. Errors or late ASNs are the primary source of Walmart chargebacks.

Critical 856 Timing Requirements

The 856 must be transmitted BEFORE the merchandise arrives at the Walmart distribution center
For most DCs: the 856 must be sent within 30 minutes of the carrier departing your facility
Some Walmart DCs require the 856 before the truck leaves your dock
The 856 must contain the exact GS1-128 pallet and carton labels applied to the shipment
Mismatch between ASN data and actual receipt → chargeback, even if shipment is physically correct

The 856 uses a hierarchical loop structure (BSN header → HL loops) to represent the physical packaging structure:

BSN*00*SHIP-001*20260420*1430*0001~     ← Shipment identification
  HL*1**S~                               ← S = Shipment level
    TD1*CTN25*48~                        ← 48 cartons
    TD3*TL*CARRIER*PRO-123456~           ← Carrier info
    REF*BM*BOL-98765~                    ← Bill of Lading number
    N1*ST*WAL-MART DC 6094*UL*0078742006094~ ← Ship-to DC (GLN)
    N1*SF*ACME SUPPLIER LLC*92*SUPP001~  ← Ship-from
    HL*2*1*O~                            ← O = Order level
      PRF*PO-WMT-20260414***20260414~    ← PO reference
      HL*3*2*P~                          ← P = Pack (pallet)
        MAN*UC*00100782340000000001~      ← SSCC-18 pallet label (GS1-128)
        HL*4*3*I~                        ← I = Item level
          LIN**UP*0012345678905~          ← UPC of item
          SN1**144*EA~                    ← Quantity shipped

810 — Commercial Invoice

The 810 is your electronic invoice. Walmart's payment terms require the 810 to be sent within 24 hours of shipment and to match the 850 PO exactly on price, UPC, and quantity shipped. Discrepancies between the 810 and 850 trigger an automatic dispute hold and delay payment — sometimes by 30+ days.

Key 810 compliance requirements: BIG segment must carry the invoice number and invoice date. IT1 line items must match PO1 lines from the 850 exactly — same UPC, same unit of measure, same unit price. The TDS (total dollar summary) segment must balance to the sum of IT1 extended amounts.

AS2 Connectivity Requirements

Walmart requires direct AS2 connectivity — no VAN intermediaries are accepted. This is a hard requirement that applies to all Walmart US, Sam's Club, and Walmart.com suppliers. As a new supplier, you must:

Obtain an AS2 ID

Your AS2 ID (distinct from your ISA06 EDI sender ID) is typically formatted as your company name or a DUNS-based identifier. Walmart assigns ISA/GS IDs during onboarding; you choose your own AS2 ID but it must be agreed upon in the trading partner agreement.

Configure your AS2 endpoint

You need an AS2 server (or an EDI platform that hosts AS2 on your behalf — SignalEDI handles this for you). The endpoint must be HTTPS (TLS 1.2+), publicly accessible, and able to return signed MDNs (Message Disposition Notifications).

Exchange certificates

You provide Walmart your AS2 certificate (public key). Walmart provides you theirs. Certificates must be X.509 v3, with SHA-256 or stronger. Self-signed certificates are accepted. Certificate validity must be at least 12 months, and you must notify Walmart 60 days before expiration.

Test the connection

Walmart's EDI team sends a test ping to your AS2 endpoint and expects a signed, synchronous MDN in response. Connectivity must be stable — Walmart monitors uptime and persistent failures generate compliance flags.

After establishing AS2 connectivity, your EDI connection must be registered in the RetailLink Supplier Portal under the EDI setup section before testing can begin.

GS1 Compliance: UPCs, GTINs, and GS1-128 Labels

Walmart was one of the earliest major retailers to mandate GS1 compliance, and its requirements remain among the strictest. Every item sold to Walmart must have a valid GS1-issued GTIN (Global Trade Item Number), which in practice means a UPC barcode issued by GS1 US under your company's GS1 Company Prefix.

GTIN Requirements

Every consumer unit (each sellable package) must have a unique GTIN-12 (12-digit UPC-A barcode)
Inner packs (if applicable) must have a unique GTIN-14 (14-digit carton barcode)
Pallet-level identification uses SSCC-18 (18-digit Serial Shipping Container Code) on GS1-128 pallet labels
Walmart requires GTINs to be registered in the GS1 US Data Hub and synced to the Global Data Synchronization Network (GDSN) via a data pool — most suppliers use 1WorldSync
The GTIN in your EDI transactions must exactly match the GTIN on the physical product label — no exceptions

GS1-128 Pallet Label Requirements

Every pallet must have a Walmart-compliant GS1-128 label. The label must include, in the correct Application Identifier format:

GS1 AI	Data Content	Required?
(00)	SSCC — 18-digit pallet serial number	Required
(02)	GTIN of contained items	Required
(37)	Quantity of contained items	Required
(420)	Ship-To ZIP code	Required
(91)	Walmart-assigned vendor number	Required
(30)	Count of trade items	Conditional
(15) or (17)	Best-by or expiration date	Required for food/pharma

Chargeback Penalties: What They Cost and How to Avoid Them

Walmart's chargeback program is comprehensive and aggressively enforced. Chargebacks are deducted automatically from payment — you receive less than you invoiced, with a deduction explanation in the 812 credit/debit statement or as a 997 rejection. Disputing chargebacks requires evidence submitted through RetailLink within 30 days.

Violation	Chargeback Amount	Prevention
No ASN / Late ASN	$250 per PO or 3% of invoice, whichever is greater	Automate 856 generation from WMS/shipping system
ASN quantity error (>5% variance)	$250 per PO	Validate ASN quantities against shipping document before transmitting
Incorrect UPC on ASN	$250 per PO per item	Sync GS1 Data Hub GTINs to EDI item master
Missing or incorrect GS1-128 label	$250 per pallet	Use label generation software integrated with EDI
Late invoice (>24 hrs post-ship)	Payment term reset, sometimes 2% penalty	Automate 810 generation from shipment confirmation
Invoice/PO price mismatch	Deduction of difference + admin fee	Validate 810 unit price against last 850 price before sending
Ship outside the PO window	Refused receipt or penalty per unit	Monitor DTM010 and DTM038 from 850; alert warehouse
Wrong item shipped (UPC mismatch)	Return freight + handling charge	Barcode scan at pack-out to validate against PO

RetailLink and Luminate: Walmart's Supplier Portals

Walmart operates two primary supplier portals that intersect with your EDI operations. Understanding their relationship is essential for managing your Walmart business effectively.

RetailLink

EDI Setup & Compliance

retaillink.walmart.com

The original Walmart supplier portal. Used for: EDI setup and testing, chargeback dispute management, invoice status, inventory reports, compliance scorecards. All EDI configuration (trading partner agreement, AS2 setup, test certification) happens in RetailLink. This is where you spend most of your setup time.

Luminate

Analytics & Insights

luminate.walmart.com

Walmart's next-generation data and collaboration platform. Provides point-of-sale data, inventory positions, replenishment recommendations, and advanced analytics. As of 2026, some EDI monitoring and transaction status tools are migrating from RetailLink to Luminate. New suppliers should set up both portals.

Testing Process and Certification Timeline

Walmart's EDI testing is structured and sequential. You cannot skip steps. The testing phase is the primary reason new supplier timelines extend to 8–12 weeks — not because the testing itself is complex, but because Walmart's EDI support team reviews submissions in queue order.

Step 1

Connectivity test

Days 1–3

Walmart sends a test AS2 transmission to your endpoint. You must return a valid signed MDN. The test is scheduled through RetailLink after your AS2 profile is configured.

Step 2

997 acknowledgment test

Days 4–7

Walmart transmits test 850s to your endpoint. You must return correctly formatted 997s within 24 hours. Walmart verifies the 997 structure before proceeding.

Step 3

855 POA test

Days 8–14

You transmit test 855 POAs in response to the test 850s. Walmart reviews ACK01 codes and segment structure. Common failures: wrong BAK01/BAK02 codes, missing or incorrect ACK loops.

Step 4

856 ASN test

Days 15–28

You transmit a test 856 with correct HL loop hierarchy, SSCC-18 pallet labels, and item quantities. This step has the highest failure rate — most commonly due to incorrect HL loop IDs or missing MAN (pallet label) segments.

Step 5

810 invoice test

Days 20–30

You transmit a test 810 matching the test 850. Walmart validates price, quantity, unit of measure, and BIG segment date format. Small formatting errors (wrong date format in BIG03) are common.

Step 6

Certification review

Days 28–56

Walmart's EDI compliance team reviews all test results. If all tests pass, they issue go-live approval. If any step has errors, the failed test must be corrected and resubmitted — the clock restarts for that step.

Go-Live Checklist

Before accepting your first live Walmart purchase order, verify each of these:

AS2 connectivity live and monitored (MDN response time < 30 seconds)

EDI ISA/GS IDs set to Production (ISA15 = 'P')

Walmart certification approval received in writing via RetailLink

856 generation workflow integrated with WMS or shipping system

856 trigger: automated on shipment confirmation, not manual

GS1-128 label printer configured and labels validated against spec

810 invoice generation automated from shipment data

997/999 acknowledgment monitoring active — alerts for rejections within 1 hour

Chargeback dispute workflow documented — who reviews, what evidence to collect, 30-day window understood

RetailLink compliance scorecard baseline established

Item master synced to GS1 Data Hub with all Walmart SKUs

Shipping window monitoring active — alerts when PO cancel date approaches

Frequently Asked Questions

Q: Can I use a third-party EDI provider to handle Walmart compliance?

Yes — most suppliers use an EDI platform or 3PL with EDI capabilities rather than building and maintaining their own system. The EDI provider handles AS2 connectivity, transaction generation, and acknowledgment monitoring. You remain responsible for the underlying business processes — getting the right UPCs on the right cartons, generating shipment data accurately, and responding to chargebacks. When choosing a provider, verify they have Walmart's current implementation guides and have supported Walmart connections before.

Q: What happens if I send an 856 late on my first shipment?

Walmart's system will likely issue an ASN non-compliance chargeback automatically. On a first shipment, some Walmart supplier development managers will work with new suppliers to reverse a first-offense chargeback if you can demonstrate a technical issue rather than a process failure. However, do not rely on this. Use test shipments during certification to validate your end-to-end ASN workflow — from shipment departure to 856 transmission — before going live.

Q: Do Walmart's EDI requirements differ for marketplace (Walmart.com) vs. store suppliers?

Yes. Store suppliers (direct-to-DC) have the traditional 850/855/856/810 requirements described in this guide. Walmart.com marketplace sellers primarily use the Walmart Seller Center API rather than traditional EDI. However, large-volume marketplace suppliers who fulfill through Walmart's fulfillment centers (WFS) do have EDI requirements similar to store suppliers. Always confirm with your Walmart buyer which program applies to your items.

Q: How do I dispute a Walmart chargeback?

Log into RetailLink → Navigate to the Compliance section → Find the specific deduction. Chargebacks can be disputed within 30 days of the deduction date. To dispute an ASN chargeback, you need: the 856 transmission log showing transmission timestamp, the signed MDN from Walmart confirming receipt, and the bill of lading with the departure timestamp. If you transmitted the 856 correctly and on time but Walmart's system failed to process it, this evidence is typically sufficient for reversal.

Q: What is Walmart's current EDI standard version — 4010 or 5010?

Walmart requires X12 004010 for most transactions in its traditional store supply chain — an exception from the general industry trend toward 005010. Walmart.com and newer digital programs may require 005010 or API-based integrations. Always verify against the current Walmart Supplier EDI Standards document in RetailLink, as version requirements can change. This is one area where an EDI platform with a maintained Walmart profile saves you significant research time.

Walmart EDI Requirements for New Suppliers: The Complete 2026 Guide