FBA vs FBM Shipping Labels: What's the Difference and Which Do You Need?

Amazon offers two primary fulfillment models: FBA (Fulfilled by Amazon) and FBM (Fulfilled by Merchant). They have completely different label workflows, and confusing the two creates real problems — labels routed through the wrong channel result in inventory holds, customer returns, and late shipment metrics.

This guide explains exactly what labels you need for each fulfillment type, when each label gets applied, what happens if you get it wrong, and how to choose the right workflow for your operation.

The FBA Label Workflow

In the FBA model, your inventory travels in two stages:

1. From your supplier/warehouse to Amazon's fulfillment center (FC) — the "inbound shipment"
2. From Amazon's FC to the end customer — handled entirely by Amazon

You are only responsible for labels on Stage 1. Stage 2 labels are Amazon's problem.

Stage 1 FBA Labels: What You Need

FNSKU Unit Labels

Every individual sellable unit that enters an Amazon FC must have an FNSKU label on the outside of its packaging. The FNSKU is a 10-character identifier (format: X001234567) unique to your seller account and ASIN.

• Format: Code 128 barcode, minimum 1"×1", white background
• Placement: On the outside of the unit's packaging, covering any existing manufacturer barcode
• Generated by: Seller Central → Manage FBA Inventory → Print Item Labels

Box Labels (Carton Labels)

Each carton you send to Amazon needs a box label — a 4"×6" label with a GS1-128 barcode identifying the specific shipment and box number.

• Format: GS1-128 barcode, 4"×6" label size
• Placement: On the side of the carton (not top or bottom)
• Generated by: Seller Central during the "Create Shipment" workflow
• Critical: Box labels are shipment-specific. Do not reuse box labels from previous shipments.

Pallet Labels (LTL Shipments Only)

If your inbound shipment ships via LTL truck freight (generally for shipments over 150 lbs or more than 15 boxes), you need pallet labels on all four faces of each pallet.

• Format: 4"×6", Code 128 barcode with pallet ID
• Placement: All four sides, in the upper third of the pallet
• Quantity: One per face, four total per pallet
• Generated by: Seller Central in the LTL shipping workflow

The FBA Label Application Process (Typical Workflow)

For sellers using a 3PL for FBA prep:

1. Your manufacturer ships inventory to the prep center
2. The prep center receives the inventory, scans it, and applies FNSKU labels (sourced from Seller Central or from your WMS)
3. The prep center packs units into cartons
4. You create the FBA shipment in Seller Central, which generates box labels
5. Box labels are printed and applied to cartons
6. If LTL, pallet labels are generated and applied
7. The shipment is picked up by the carrier

Many WMS and ERP systems output FNSKU label data as ZPL files, which prep centers need to convert to PDFs for printing on non-Zebra hardware or for record-keeping. This is where tools like Zentralabel come in — converting batches of ZPL label files to print-ready PDFs without requiring a Zebra printer on every workstation.

The FBM Label Workflow

In the FBM model (also called MFN — Merchant Fulfilled Network), you receive an order through Amazon and ship directly to the customer yourself. Amazon does not handle the physical fulfillment.

What Labels FBM Requires

Carrier Shipping Label

This is the primary label for FBM. It includes the ship-to address, ship-from address, a carrier tracking barcode, and service class. You generate this through:

• Buy Shipping in Seller Central — Amazon's native carrier label tool (UPS, USPS, FedEx, DHL). Recommended because it auto-confirms shipment to Amazon.
• Your own carrier account — ship via your UPS/FedEx/USPS account and manually confirm shipment in Seller Central.
• Third-party shipping software — ShipStation, Shippo, EasyPost, etc.

The carrier label is typically 4"×6" in ZPL format from carrier APIs, or 4"×6" PDF from web portals.

Amazon's requirement: You must confirm shipment with a valid tracking number within the handling time you set for your listings (typically 1-2 business days). Late shipment rate above 4% triggers account metrics warnings.

Packing Slip

FBM orders should include a packing slip inside the package — a summary of the order contents, order ID, and ship-to address. Amazon's packing slip template is accessible in Seller Central → Orders → Manage Orders → Print Packing Slip.

The packing slip is not technically a "label" but it is a required document per Amazon's FBM guidelines. Customers and Amazon both use it for return processing.

No FNSKU Label Required

FBM orders ship directly to customers. There is no FNSKU label needed because the item never enters Amazon's FC. The carrier label is the only barcode label required.

Multi-Channel Fulfillment (MCF) Labels

Multi-Channel Fulfillment (MCF) is a hybrid model: your inventory lives in Amazon's FCs (you used FBA to send it there), but Amazon fulfills orders from other sales channels (your Shopify store, eBay, etc.) using that inventory.

MCF Label Specifics

For MCF orders:

• Inventory in the FC: Already has FNSKU labels (applied when you sent it in)
• Outbound label: Amazon generates the carrier shipping label for MCF orders automatically
• Packing slip: Amazon's default MCF packing slip says "Fulfilled by Amazon" — you can request "blank box" fulfillment for an extra fee to suppress Amazon branding

You do not apply labels to MCF outbound shipments. Amazon handles all outbound labeling from their FCs. Your labeling responsibility for MCF is identical to standard FBA — apply FNSKU labels to units before sending them to the FC.

Dropshipping Label Rules

Amazon's dropshipping policy is strict: you may fulfill orders by purchasing from a supplier who ships directly to the customer, but the package must arrive with your seller information as the shipper, not the supplier's.

This means:

• The carrier label must show your company as the shipper (not the supplier's company)
• No packing slips or marketing materials from the supplier may be included
• The package must not suggest the customer purchased from a third party

Common violation: A dropshipper who uses an Alibaba supplier's direct shipping, which includes Chinese-language packing slips and the supplier's brand markings. This violates Amazon's policy and can result in account suspension.

For compliant dropshipping, the supplier must be instructed to use generic packaging, your seller information on the carrier label, and no third-party branding.

What Happens If You Mix Up FBA and FBM Labels

FBM label applied to an FBA inbound shipment

If you send boxes with FBM carrier labels (addressed to a customer) to an Amazon FC instead of using the proper box labels — the FC receiving dock will refuse the shipment. Box labels must encode the shipment ID format that Amazon's WMS expects.

In practice, this error is hard to make if you follow the Seller Central workflow, since box labels are generated within the shipment creation process. It's more likely to happen if someone grabs the wrong printed labels at a prep center.

FNSKU label missing from units in FBA shipment

Units that arrive at the FC without FNSKU labels (or with unreadable ones) are flagged as "problem items." Amazon will either:

1. Charge you a labeling fee ($0.20/unit as of 2026) to apply labels at the FC
2. Return the units to you if the products are in a restricted category that requires FNSKU

The labeling service fee adds up quickly for large shipments. A 500-unit shipment with missing labels costs $100 in unexpected fees.

FBA FNSKU label on an FBM order

If you accidentally ship an FBM order in a box that has an FNSKU label or Amazon FC box label on the outside, the carrier will still deliver it — carrier labels take precedence for routing. However, customers may be confused by the Amazon-internal label markings, and it creates a professional presentation issue.

Cost Comparison, Checklists, and Choosing Your Model

Cost Comparison: FBA Labeling vs FBM Labeling

For high-volume operations, FBA's labeling cost (especially if using Amazon's labeling service) can exceed FBM's label costs — but FBA eliminates the labor and carrier cost of individual order fulfillment, which usually makes it the lower total cost at scale.

Practical Checklist by Scenario

Sending an FBA inbound shipment

• Every unit has an FNSKU label (Code 128, min 1"×1", white background)
• FNSKU label covers any existing manufacturer barcode
• Every carton has the correct box label from Seller Central
• Box labels match the carton's declared contents
• If LTL: pallet labels on all four faces of each pallet
• Shipment confirmed in Seller Central before carrier pickup

Fulfilling an FBM order

• Carrier shipping label generated (via Buy Shipping or your carrier)
• Tracking number entered in Seller Central before handling time deadline
• Packing slip printed and included in the package
• No supplier branding or third-party packing materials in the box
• Package weight and dimensions match what was declared

Setting up an MCF order

• Inventory already at Amazon FC with FNSKU labels (standard FBA process)
• MCF order placed in Seller Central or via MCF API
• If using "blank box" service: option selected in MCF settings
• Tracking number flows back to your sales channel

Choosing Between FBA and FBM: The Label Workflow Perspective

From a pure labeling standpoint:

FBA is more complex up front (FNSKU labeling, box labels, occasional pallet labels) but eliminates all per-order fulfillment work. Once inventory is at the FC, Amazon handles all outbound labels.

FBM is simpler for inbound (no FNSKU required) but requires generating and applying a carrier label for every single order, which adds meaningful labor at volume.

For sellers processing ZPL-format carrier labels from UPS/FedEx/USPS APIs as part of an FBM or hybrid workflow, converting those ZPL files to PDFs for printing on standard office printers or archiving is a common operational need. Zentralabel handles batch ZPL-to-PDF conversion for exactly this use case.

Whether you're running FBA inbound at a 3PL, managing FBM order fulfillment in-house, or operating a hybrid MCF strategy, the label workflow is a surprisingly significant operational lever — getting it right reduces costs, prevents account flags, and keeps inventory moving.

Start streamlining your label workflow today at Zentralabel.