By Bernardo Campelo, Forbes Business Council E-Commerce Leader, Amazon SPN Certified provider, Amazon SP-API authorized partner, and Founder of PrepVia.
A wholesale buyer posted the same question in a forum this past March. Her distributor already sends an EDI 856 the moment a truck leaves the dock, and she wanted to know exactly where that electronic document was supposed to meet the physical pallet her prep center built for Amazon. Three replies gave three different answers, and none of them separated the three things she was actually asking about: the case pack, the pallet, and the message riding on top of both.
That confusion shows up in search behavior too. A results census run on September 23, 2026 found that seven of nine results for the phrase wholesale FBA prep already belong to a prep center's own service or pricing page, not a general logistics guide. Anyone typing that phrase already knows what a prep center does. What they cannot find is a straight answer on how a case pack becomes a pallet, and where EDI fits into the shipment.
The physical flow and the electronic flow are two separate systems that happen to describe the same shipment. A wholesale seller who treats them as one problem ends up either building EDI capability nobody on the Amazon side asked for, or skipping it right up until a real distribution partner demands it.
The 60-second version
A wholesale shipment runs through two systems at once, the physical pallet and the electronic paperwork, and most confusion comes from treating them as the same thing. The case pack quantity a distributor sets determines whether Amazon receives sealed cases or requires a case break down to the unit. A master carton label identifies the case on the pallet, while a unit label, most often an FNSKU, identifies the single item once Amazon scans it into inventory. The seller picks small parcel or LTL in Send to Amazon. Amazon suggests a partnered LTL or FTL carrier once a shipment weighs more than 150 pounds, and a partnered shipment of more than 12 pallets is rolled into a full truckload. Electronic Data Interchange, the 850 order, the 856 shipment notice, and the 810 invoice, becomes a practical requirement only once a seller trades directly with a distributor or retail partner that demands it, not simply because the seller also holds an Amazon Vendor Central account.
The Case Pack Order: What Actually Shows Up on the Pallet
A wholesale order does not move in units. It moves in case packs, a fixed quantity of identical items sealed inside one manufacturer carton, and the case pack number is set long before the prep center ever sees the freight. A distributor selling paper towels in case packs of twelve is not going to break that carton to sell eleven, and a buyer placing a purchase order is really placing an order in cases, with the unit count following as a multiplication problem.
The pallet that arrives at a prep center is a stack of those sealed cases, built to a pattern the distributor chose for stability in transit, not for Amazon convenience. A standard pallet might carry forty to sixty cases stacked in interlocking layers, shrink wrapped, with a packing slip taped to one side or, on a better run operation, emailed ahead as a file. That packing slip lists the SKU, the case count, and the units per case for every case on the pallet, and it is the single most important piece of paper in the shipment, because receiving checks everything against it.
For the wholesale and distribution clients we work with, the case pack number is a decision with consequences that outlast the purchase order. A case of twelve identical units moves through Amazon receiving fast, since the case packed requirement lets Amazon scan one unit and credit the whole case. A case of thirty six units that has to split across two fulfillment centers in a ratio the case count does not divide evenly turns into a case break before it ever reaches Amazon, and that decision belongs in the order conversation with the distributor, not discovered on the receiving dock.
Receiving the Pallet, Verifying the Case
Receiving a wholesale pallet is a counting exercise at two different levels, and skipping either one is how a shortage goes unnoticed until a chargeback or a rejected reimbursement claim shows up weeks later. The first count happens at the pallet level, against the bill of lading the carrier hands over at the dock: pallet count, total weight, and any visible damage noted before anyone signs for the freight.
The second count happens inside each pallet, case by case, against the packing slip. A receiving team breaks down the shrink wrap, counts sealed cases, and checks that number against what the packing slip promised for that SKU. This step catches a failure mode that pallet counting alone misses: a pallet can arrive with the correct case count and still be short, because a case that should hold thirty units only holds twenty four inside a sealed carton nobody opened.
Open case verification on a sample of cartons closes that gap. A receiving team that opens one case in ten and counts the actual units inside catches a packing error before it becomes an Amazon shortage claim instead of after. This mirrors the receiving discipline covered in more depth in our wholesale FBA prep workflow guide, which walks through the full sampling and reconciliation process pallet by pallet.
When Amazon Wants the Unit, Not the Case
Amazon accepts a case packed shipment only when every unit inside the case is identical in SKU and condition, the case holds the same quantity as every other case of that SKU, and the case itself stays under the packaging limits Amazon sets for a case packed carton. A distributor case meets that bar more often than not, which is the appeal of shipping case packed in the first place: the case moves as one scan instead of dozens.
The case breaks apart the moment any of those conditions fail. A shipment plan that splits units across two fulfillment centers in a ratio the case count does not divide evenly forces a break, since Amazon will not accept a partial case. A case that mixes two SKUs under one barcode, common with promotional multi packs, forces a break because Amazon requires single SKU cases for case packed eligibility, a rule covered in our breakdown of FNSKU versus UPC versus manufacturer barcode. A case that exceeds the fifty pound single carton limit without holding one oversize unit forces a break regardless of how clean the packaging looks.
Once a case breaks, every unit inside it needs its own barcode before it can go back into a box bound for Amazon, and that labeling step is where volume and speed actually matter. A prep center running unit level labeling at scale, rather than a person with a sticker gun, is the difference between a same week turnaround and a shipment that sits in queue.
Master Carton Label vs Unit Label
Two different labels do two different jobs on the same pallet, and confusing them is one of the more common ways a wholesale shipment stalls. A master carton label identifies the case itself: the SKU, the quantity inside, and, for freight moving to a distribution center rather than an Amazon fulfillment center, a GS1-128 pallet or case label that a warehouse management system scans to track the carton without opening it.
A unit label identifies one single item. For an Amazon bound shipment, that is most often an FNSKU, the barcode Amazon generates for a specific seller and a specific SKU, applied directly over the manufacturer UPC so a fulfillment center scanner can never read the wrong code by mistake. A unit label has to survive the trip: thermal printed, never inkjet, since inkjet ink smears under a shrink wrap and goes unreadable long before the case reaches Amazon, a failure mode covered directly in our piece on FNSKU mis-scans and print quality.
| Master Carton Label | Unit Label | |
|---|---|---|
| What it identifies | The sealed case, as one countable object on the pallet | One single item inside the case |
| Where it goes | On the outside of the carton, usually one per case | On the item itself, applied over the manufacturer barcode |
| When Amazon needs it | Case packed shipments, so a fulfillment center can scan one unit and receive the whole case | Every unit a reseller sends, even over a manufacturer UPC, since March 31, 2026; only a brand representative in Brand Registry can use the manufacturer barcode instead |
| Who applies it | The manufacturer or distributor, before the case ever ships | The prep center, at labeling, for any case that breaks or was never case eligible |
A prep center running wholesale volume can print and apply thousands of unit labels a day, closer to an industrial line than a hand process, work that a dedicated FBA labeling service is built around. PrepVia measures accuracy across that prep work at 99.9 percent, a figure worth asking any prep partner to produce before trusting a large case break to them.
SPD or LTL: Where the Line Sits
Amazon routes an inbound shipment through one of two transportation programs, and the choice belongs to the seller, made in Send to Amazon. Amazon does not force LTL at any volume. It suggests considering a partnered LTL or FTL carrier once the total shipment weighs more than 150 pounds, so in practice the number of boxes and pallets the shipment plan generates is what drives the decision. Small parcel delivery, SPD, moves individual boxes through a parcel carrier, one box, one tracking number, one delivery scan. Less than truckload freight, LTL, moves boxes stacked and shrink wrapped on pallets, billed by weight and freight class rather than by box.
Wholesale volume crosses into LTL territory earlier than most sellers expect, often well before a shipment fills anything close to a full truck. Once a shipment plan generates enough boxes to build even a handful of full pallets, LTL becomes cheaper per unit and, just as important, faster to receive, since an Amazon fulfillment center processes a pallet of sealed cases far quicker than the same unit count arriving as loose parcels over several days. A full comparison of the cost and speed tradeoffs sits in our SPD versus LTL breakdown, worth reading before committing a wholesale shipment plan to either program.
The case pack decision from earlier in this flow feeds directly into this choice. Case packed freight builds clean, stable pallets. Loose or broken case freight often has to be boxed before it can palletize at all, which adds a packing step LTL does not usually need for a distributor shipment that already arrived sealed.
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Scheduling the Pallet for Pickup
An LTL pallet does not leave a prep center dock without an appointment. Amazon's partnered carrier program books that pickup once a shipment plan is confirmed, a process covered in more detail in our guide to partnered carrier fee adjustments, and the carrier that shows up expects the freight staged, counted, and labeled before the truck arrives, not while it waits at the dock door.
Turnaround from a confirmed shipment plan to a carrier pickup is a measurable number, not a guess, and it is worth asking a prep partner for their own figure rather than accepting a vague promise. Measured across PrepVia shipments through September 2026, the median time from creating a shipment to carrier pickup runs 30.2 hours. That number moves with how clean the case pack arrived and how much of the freight needed a case break before it could palletize.
Missing a booked pickup window costs more than a rescheduled truck. A pallet sitting an extra day waiting on a new appointment is inventory not yet counted at the fulfillment center, and for a wholesale seller running tight replenishment cycles, that delay compounds across every SKU on the pallet. Tracking the pallet once it leaves the dock follows the same PRO number logic explained in how to track an FBA LTL shipment.
Where EDI Actually Begins, and Who Really Needs It
The Three Documents That Matter
Electronic Data Interchange is a standard for exchanging business documents as structured data instead of a phone call or a PDF, and in a wholesale relationship, three documents do almost all of the work. An EDI 850 is the purchase order itself, transmitted from the buyer, a distributor, a retailer, or Amazon acting as a buyer through Vendor Central, specifying SKU, quantity, cost, and a requested delivery date. An EDI 856, the advance ship notice, travels the other direction before or at pickup, describing exactly what is on the truck down to the case and pallet level. An EDI 810 is the invoice, sent after delivery, closing the transaction on the seller's side.
| EDI Document | Who Sends It | Who Receives It | Does a Typical Wholesale Seller Need It |
|---|---|---|---|
| 850, Purchase Order | The buyer: a distributor, a retailer, or Amazon through Vendor Central | The seller or vendor | Only if selling directly to a retail or distribution partner that issues orders electronically |
| 856, Advance Ship Notice | The seller or vendor, before or at pickup | The buyer's receiving system | Usually required once a trading partner relationship moves past a handful of orders a week |
| 810, Invoice | The seller or vendor, after delivery | The buyer's accounts payable system | Common once the buyer demands electronic billing instead of a paper or PDF invoice |
Who Actually Needs It
A seller who sells exclusively through Amazon Seller Central, even at real wholesale volume, does not need EDI at all. Amazon's own FBA shipment creation process runs through the Seller Central web interface or the Selling Partner API, and neither one speaks EDI to the seller. The confusion in that forum post from March traced back to exactly this point: her Amazon side of the business never touched EDI, only her distributor relationship did, and the two systems were never going to meet on the same pallet the way she expected.
EDI becomes close to a practical requirement in two situations. The first is a Vendor Central relationship at real purchase order volume, where Amazon issues the 850 and expects the 855 acknowledgment and 856 advance ship notice back on a schedule a person cannot key by hand past a few orders a week. The second is a direct wholesale relationship with a retailer or distributor outside Amazon entirely, a big box account or a regional grocery chain, where the buyer's own system requires EDI as a condition of doing business at all, independent of anything happening on Amazon.
What a prep center controls in either case is the physical shipment, not the electronic document. PrepVia builds the case pack, applies the labels, and stages the freight to match the paperwork already in a client's hands, but PrepVia does not transmit EDI documents on a client's behalf. An accurate 856 sitting on a pallet that does not match it is worse than having no advance ship notice at all, since it tells the receiving system to expect something the dock will not find.
Frequently Asked Questions
What is a case pack in wholesale FBA prep?
A case pack is a fixed quantity of identical units sealed inside one manufacturer carton, set by the distributor before the order ships. The case pack number determines whether Amazon can receive the shipment as sealed cases or whether a case break down to the unit becomes necessary once the shipment plan splits inventory across fulfillment centers.
When does Amazon require a case break instead of a sealed case?
Amazon requires a case break whenever a case mixes more than one SKU, whenever a shipment plan splits units across fulfillment centers in a ratio the case count does not divide evenly, or whenever a case exceeds the fifty pound single carton limit without holding a single oversize unit. Any of these conditions forces every unit inside that case to be labeled and boxed individually.
What is the difference between a master carton label and a unit label?
A master carton label identifies the sealed case as one object on the pallet, usually applied by the manufacturer or distributor before the case ships. A unit label, most often an FNSKU for an Amazon bound shipment, identifies a single item inside the case and is applied over the manufacturer barcode so a fulfillment center scanner reads only the correct code.
When should a wholesale shipment move as LTL instead of small parcel?
A shipment plan that generates enough boxes to build even a few full pallets typically becomes cheaper and faster to receive as LTL freight than as small parcel. Case packed freight, already sealed and stable, palletizes cleanly, while loose or broken case freight often needs boxing before it can build a pallet at all.
Do I need EDI to sell wholesale through Amazon FBA?
A seller running FBA exclusively through Seller Central does not need EDI at all, since Amazon's own shipment creation tools work through the web interface or the Selling Partner API. EDI becomes close to a practical requirement only with a Vendor Central account at real purchase order volume or with a direct wholesale relationship to a retailer or distributor that requires it as a condition of doing business.
What is an EDI 856 advance ship notice?
An EDI 856 is the electronic document a seller or vendor transmits before or at pickup, describing exactly what is on the truck down to the case and pallet level. The receiving system uses it to expect a specific shipment, which is why the physical pallet has to match the 856 exactly, since a mismatch at the dock causes more trouble than having no advance ship notice at all.
Does PrepVia transmit EDI documents for its clients?
No. PrepVia builds the case pack, applies the carton and unit labels, and stages the freight to match the paperwork a client already has in place, but PrepVia does not transmit EDI documents on a client's behalf. That electronic exchange sits with the client's own EDI provider or trading partner relationship, separate from the physical prep work.
Final Take
A wholesale shipment is really two shipments moving in parallel, a stack of physical pallets and a set of electronic documents describing them, and the two rarely fail for the same reason. The physical shipment fails on a case count that does not match a packing slip, or a unit label that does not survive the trip. The electronic shipment fails on a document describing cargo the dock never received, or on a trading relationship that never needed EDI and adopted it out of habit.
Getting the case pack decision right at the order stage prevents most of what goes wrong downstream. A case count that divides cleanly across a shipment plan avoids a case break entirely. A case pack specification shared with the prep center before the truck leaves the distributor avoids a receiving surprise. Neither decision has anything to do with EDI, and treating them as the same problem is how a seller ends up building a document exchange nobody on the Amazon side ever asked for.
EDI earns its place only where the paperwork volume actually justifies it, a Vendor Central account running real purchase order volume or a direct account with a retailer or distributor that requires it. Below that line, a seller running FBA wholesale through Seller Central can operate entirely without it, and the effort spent standing up an EDI relationship is better spent getting the case pack, the pallet, and the labels right the first time.
Ask any prep partner handling wholesale freight the same question that forum post from March never got a straight answer to: where does the physical shipment end and the electronic one begin. A partner who can answer that clearly, case by case, pallet by pallet, document by document, is the one worth trusting with a truck instead of a parcel.
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