TL;DR
- FNSKU labels are required on every unit, must be the only scannable barcode visible, and need a flat placement surface.
- Polybags must be at least 1.5 mil thick, transparent, and carry a suffocation warning when openings measure 5 inches or larger.
- Hazmat units have separate fees, separate workflows, and require liquid bagging regardless of size.
- Amazon is discontinuing FBA prep and labeling in the US starting January 2026, which is why third-party prep is more important than ever.
Why FBA prep is not optional and what happens when it is wrong.
Amazon's fulfillment network is built for high throughput and low handling time. The entire receiving and stowing process at an FBA warehouse runs on the assumption that every unit has a clean FNSKU label, the right packaging, the right case pack, and the right paperwork. When a unit fails any of those checks, it gets pulled out of the line. Pulled units accumulate, get billed back to the seller as Unplanned Service Fees, and often sit for days while Amazon decides what to do.
The cost of a single non-compliant pallet is small. The cost of a recurring compliance problem is large. Stranded inventory does not earn revenue, sits against storage caps, and frequently triggers IPI (Inventory Performance Index) penalties that throttle future inbound capacity. For sellers running close to peak season storage limits, a compliance issue at the wrong moment can lock new inbound for weeks.
The stakes climbed in late 2025 when Amazon announced it was winding down its in-house FBA prep and labeling services in the US starting January 2026.[7] Sellers who relied on Amazon to apply FNSKU labels or polybag bare units now need to handle prep before inbound or work with a third-party prep center. The transition is straightforward for sellers already using a 3PL. It is harder for sellers who never needed prep capability before.
FNSKU labels: the rule that matters most.
Every FBA unit needs a unique FNSKU (Fulfillment Network Stock Keeping Unit) label that ties the physical unit to the seller's account in Amazon's system. The label is the ground truth at receiving. If a unit lacks an FNSKU, has a damaged FNSKU, or has any other competing barcode visible (a UPC, an EAN, a manufacturer barcode), the unit fails the scan and stops the line.[2]
The mechanical rules are tight. The label must measure 1 by 2 inches, be easy to read, and sit on a flat surface, not a corner or curve.[2] The label must be the only scannable barcode visible on the outermost packaging.[2] If the manufacturer barcode is on the same surface as the FNSKU, it has to be covered with an opaque sticker before the FNSKU goes on. Otherwise the receiving scanner has a 50/50 chance of grabbing the wrong code, and the unit ends up associated with the wrong ASIN.
FNSKU label essentials
| Rule | Detail | Common failure |
|---|---|---|
| Size | Roughly 1 inch by 2 inches | Too small to scan |
| Placement | Flat surface, not corner or curve | Wraps around an edge and fails to scan |
| Other barcodes | Must be only scannable code | Manufacturer UPC left visible |
| Print quality | High contrast, no smudging | Low-quality printer or wet ink |
| Adhesion | Stays attached through receiving | Falls off in transit |
Polybag, bubble wrap, and what triggers each.
Polybagging requirements exist because Amazon's network handles a lot of units. Loose, unprotected items get damaged, and damaged units become customer-service problems and inventory write-offs. The rule is direct: poly bags used for FBA must be at least 1.5 mil thick and completely transparent so the FNSKU stays scannable through the bag.[3]
Polybags with openings of 5 inches or more (measured flat) require a suffocation warning printed on the bag.[3] The exact text is specified by Amazon: "WARNING: To avoid danger of suffocation, keep this plastic film away from babies and children. Do not use this bag in cribs, beds, carriages, or play pens. This bag is not a toy." Font size scales with bag size, from 10 point on bags under 29 inches combined length and width to 24 point on bags 60 inches and larger.[3]
Bubble wrap or other protective packaging applies to fragile items: glass, ceramics, sharp edges, electronics. The bubble wrap should fully encase the unit so a finger pressed against the package cannot feel a hard edge. Bubble wrapped items still need an FNSKU on the outside, which means the label goes on the bubble wrap, not the inner packaging.[4]
Case pack requirements that keep inbound moving.
Case packs are how Amazon receives units in bulk. A case pack is a master carton containing a standard quantity of one SKU, with the case pack quantity declared in the inbound shipment plan. Amazon prefers consistent case packs because they let the receiving team count once at the case level instead of unit by unit. The benefit shows up as faster check-in and reduced reconciliation discrepancies.
For prep purposes, every case pack needs a case-level FNSKU label on the outside, individual FNSKUs on each unit inside, and the right packaging inside the case to protect the units. Cases must not exceed 50 pounds each (with some exceptions for oversized items), and units inside should be the same SKU at the same case-pack quantity. Mixed cases work for ecommerce fulfillment but cause friction at FBA receiving.
Pallet shipments to FBA have their own rules: 40 by 48 inch GMA-spec pallets, maximum 72 inches tall (including the pallet), pallet wrap on every layer, and a pallet-level label with the FBA shipment ID. Floor-loaded trailers (which Amazon increasingly accepts for high-volume sellers) follow different rules and require pre-approval.
Hazmat: the prep workflow that runs on its own track.
Dangerous goods at FBA cover a wider range than most sellers expect. Lithium batteries in electronics, aerosols in beauty, alcohol-based cleaners, magnetized products, and many sealed liquids all fall under Amazon's hazmat program. Sellers must classify products before sending them to FBA, and Amazon may require a Safety Data Sheet (SDS) and an Exemption Sheet for certain categories.[5]
The packaging rules for hazmat are stricter. All hazmat liquids require bagging, regardless of size or original packaging.[5] Pressurized aerosols need protective packaging that resists puncture. Lithium-ion batteries (whether bare or installed in devices) follow IATA and DOT rules that affect how the case is labeled and how the inbound is routed. Hazmat units pay slightly higher monthly storage fees and slightly higher fulfillment fees than non-hazmat equivalents (typically $0.06 to $0.16 per unit per month for storage and $0.06 to $0.11 per unit for fulfillment).[7]
Amazon receiving SLAs and what slows them down.
Amazon publishes a target of three to seven business days for inbound to be received and available to sell, but actual times vary by destination FC, time of year, and shipment quality. Q4 receiving routinely runs longer because inbound volume spikes at every FC. High-quality inbound (clean labels, accurate case counts, correct shipment plan) tends to receive faster because it does not require manual reconciliation.
The most common SLA delays trace back to inbound issues, not Amazon itself. A shipment that arrives without an FBA shipment ID on the outside, or with a different unit count than the shipment plan declared, gets diverted for manual handling. A pallet that fails stability standards at the door gets refused. Inbound that arrives at the wrong FC (because the seller did not follow the routing instructions Amazon generated) gets rerouted at the seller's expense.
Per-unit prep cost benchmarks in 2025-2026.
Third-party prep service pricing settled into a fairly tight range over the last two years. Basic FNSKU labeling runs roughly $0.40 to $0.60 per unit. Polybagging adds $0.30 to $0.70 per unit depending on bag size and whether the suffocation warning is included. Bubble wrapping runs $0.80 to $1.50 per unit. Case repacking, sticker removal, and inspection services add per-unit charges on top.[6]
Approximate 2025-2026 third-party prep service pricing
| Service | Per-unit cost | When it applies |
|---|---|---|
| FNSKU labeling | $0.40 to $0.60 | Every FBA unit |
| Polybagging | $0.30 to $0.70 | Loose units, suffocation risk |
| Bubble wrap | $0.80 to $1.50 | Fragile items |
| Suffocation warning print | Included with bag | Bags with 5 in+ openings |
| Bundle prep (multi-unit) | $0.50 to $1.50 | Bundle ASINs |
| Hazmat handling | $0.10 to $0.30 surcharge | Dangerous goods |
| Repacking damaged inbound | $0.50 to $1.00 | Vendor packaging issues |
Volume drives meaningful discounts. A seller running 50,000 units per month through a single prep center pays materially less per unit than a seller running 500 units per month. The other lever is prep at the source: many overseas suppliers can apply FNSKU labels and polybag at the factory for a fraction of US prep cost, with the trade-off of tighter coordination on label files and quality checks before inbound ships.
“Prep cost per unit is small. The cost of a stranded inbound shipment is large. The math always favors getting prep right the first time.”
SIPP, low-prep packaging, and the 2026 deadline.
Amazon's Ships in Product Packaging (SIPP) program rewards sellers whose product packaging is durable enough to ship without an Amazon overbox. Qualifying products earn reduced fulfillment fees, since Amazon does not have to add a shipping carton.[9] The catch is that SIPP packaging has to meet specific durability standards, which means the product packaging itself doubles as the shipping package and survives a multi-zone parcel journey without crumbling.
For the 2026 cycle, sellers with SIPP-eligible products should validate their packaging against the current standard. Packaging that qualified two years ago may not qualify today as Amazon tightens criteria. The fee savings are meaningful at scale, but the packaging redesign cost is real.
How Warpspeed runs FBA prep.
Warpspeed runs FBA prep alongside the same fulfillment infrastructure that handles ecommerce, retail, and B2B. For Amazon sellers that means inbound from a manufacturer can land at the warehouse, get prepped to FBA spec, and ship to the right FC under one roof. FNSKU labels print at receiving from the seller's Amazon account. Polybag and bubble wrap rules are baked into the SOP per SKU, so each unit is handled the same way on every receipt.
For sellers caught by the January 2026 wind-down of Amazon's in-house prep, the transition is straightforward. We pick up the SKUs that previously relied on Amazon labeling, run them through the prep line with the seller's existing FNSKU library, and stage the prepped inbound for shipment under whatever transportation lane fits best (parcel, LTL, or carton-routed FTL for high-volume sellers).
The other half is reporting. Sellers see prep volume by SKU, defect and rework rates, and a per-unit cost roll-up that ties back to the FBA fee schedule. That visibility is what turns prep from a black-box service into a tunable cost line.
Need an FBA prep partner that gets it right the first time.
Talk to our team about FNSKU labeling, polybag and bubble wrap, hazmat workflows, SIPP qualification, and inbound routing.