Amazon Fundamentals
Amazon FBA Prep Requirements: Labels, Bags, Cartons
Amazon FBA prep requirements broken down by product type. FNSKU labels, poly-bag suffocation warnings, carton limits, and prep center vs self-prep math.
Amazon FBA prep requirements are the single largest source of avoidable fees for new and mid-size sellers. Miss the FNSKU label, forget the suffocation warning on a poly-bag, or ship a carton over the 50-pound limit and Amazon charges unplanned prep fees, delays receiving, or refuses the shipment entirely. The rules exist in Seller Central, but they’re spread across a dozen help pages and Amazon updates enforcement without much warning.
This post walks through what Amazon actually inspects at receiving, the prep required for each common product category, and the math on when a third-party prep center starts to make sense.
What does Amazon check when a shipment arrives at the fulfillment center?
Amazon’s receiving process is faster and less forgiving than most sellers assume. Cartons move through a scanning station where associates verify the shipment ID matches, count units, scan the FNSKU on each unit or case pack, and inspect prep for the SKU’s category. Anything that doesn’t scan or doesn’t match the shipping plan gets pulled aside.
Three checks matter most. The first is barcode readability, if the FNSKU doesn’t scan cleanly, Amazon either applies its own label at a per-unit fee or holds the units. The second is prep compliance for the category, poly-bagged items need the right thickness and warning, expiration-dated items need visible dates, and sold-as-set items need “sold as set” stickers. The third is carton integrity, damaged, overweight, or oversized cartons get flagged.
Rejection isn’t always outright refusal. More often Amazon accepts the shipment but charges unplanned prep or labeling fees, which show up on your payments report weeks later. That delay is the reason so many sellers don’t realize they have a prep problem until margins have already leaked. For a broader view of how FBA fees stack up against selling costs, the FBA vs FBM breakdown covers the full comparison.
Note: Amazon’s specific prep enforcement varies by warehouse and can change without public notice. This reflects current public guidance in Seller Central plus common seller community observation.
How do FNSKU labels work and where do they go?
The FNSKU (Fulfillment Network Stock Keeping Unit) is Amazon’s internal barcode. It’s generated when you create a shipping plan and it ties a specific unit to your seller account and SKU. Without an FNSKU, Amazon’s fulfillment system can’t route the unit to the right listing.
Label specs per Amazon Seller Central FBA labeling guidance:
- Size: 1 x 2 5/8 inches (Avery 5160 or equivalent) is standard, though Amazon accepts a range of sizes as long as the barcode scans.
- Print quality: Thermal printer or laser printer at 300+ DPI. Inkjet prints smear and cause scan failures.
- Placement: On a flat surface, not wrapped around an edge or corner. Must cover any existing UPC, EAN, or manufacturer barcode.
- Coverage of other barcodes: Every scannable barcode on the outside of the unit must be either covered by the FNSKU sticker or by a separate opaque sticker.
The most common FNSKU failure is placing the label on shrink-wrap that later peels off, or on a curved surface where scanners miss part of the barcode. Flat outer surface, opaque sticker material, and thermal printing solve 95% of scanning issues.
If you’re managing dozens of SKUs, the FNSKU workflow gets tedious fast. Understanding what Amazon FBA actually involves end-to-end makes the labeling step easier to systematize, and the Amazon FBA calculator helps you see whether the labeling fee is worth absorbing on lower-margin SKUs.
What are the poly-bag and packaging requirements?
Poly-bagging is where new sellers lose the most money to unplanned prep. The rules per Amazon’s packaging and prep requirements page:
- Thickness: Minimum 1.5 mil (0.0015 inches). Anything thinner tears in the fulfillment center and triggers rebag fees.
- Transparency: Bag must be transparent so associates can identify contents without opening.
- Sealing: Fully sealed, either heat-sealed, taped, or self-adhesive strip. Twist-ties and rubber bands are not accepted.
- Suffocation warning: Required on any bag with an opening 5 inches or larger. The warning language must match Amazon’s approved text.
- Warning font size: 24-point for bags with total opening dimensions of 60 inches or more, 10-point for smaller bags.
- Barcode visibility: FNSKU must be scannable through the bag or on the outside of the bag.
Small items shipped in sub-1.5 mil bags almost always get flagged. The fix is buying poly-bags rated 2 mil or thicker from a packaging supplier, which costs roughly a penny more per unit but eliminates rebag fees running $0.30 to $1.00 per unit.
Bubble-mailer and bubble-wrap requirements are separate. Fragile items need bubble wrap covering the entire product with at least 2 inches of protection on all sides. Glass items shipped without this level of protection get flagged as improperly prepped even if nothing is broken on arrival.
What are the carton and pallet rules that cause the most rejections?
Carton dimensions and weight are hard limits, not guidelines. Amazon’s standard carton limits:
| Constraint | Standard Limit | Oversize Exception |
|---|---|---|
| Weight | 50 lbs | Up to 50 lbs per carton for oversize items, single-unit cartons over 50 lbs allowed with team-lift labels |
| Longest side | 25 inches | 63 inches for oversize |
| Middle side | 25 inches | 30 inches for oversize |
| Shortest side | 25 inches | Follows oversize dimensions |
| Total combined dimensions | 63 inches | 108 inches for oversize |
Cartons over 50 lbs without a “Team Lift” label on all four sides get refused or charged unplanned service fees. Cartons over 100 lbs need a “Mechanical Lift” label and Amazon’s prior approval for the shipment.
Pallet requirements add another layer. Pallets must be 40 x 48 inch four-way GMA Grade B or better, wrapped in clear stretch wrap, and stacked no higher than 72 inches including the pallet itself. Mixed-SKU pallets need a case-pack label on every carton and Amazon’s LTL carrier program handles the pickup.
The most common carton mistake is padding a light shipment into a large box that exceeds dimension limits, or shipping heavy dense products in a carton that clears dimensions but blows past the 50-pound weight cap. Both cause receiving delays that can leave inventory in “researching” status for days or weeks, sometimes rolling into stranded inventory problems if the units get separated from their shipment record.
How does prep vary by product category?
Prep requirements aren’t uniform. Amazon groups categories by risk of damage, contamination, or safety issue, then applies specific prep rules per group.
| Category | Required Prep | Common Miss |
|---|---|---|
| Apparel | Poly-bag with suffocation warning, FNSKU on bag | Missing warning on bag opening ≥5 inches |
| Baby products (soft) | Poly-bag with warning, FNSKU on bag | Using bag under 1.5 mil |
| Liquids (leak potential) | Double poly-bagged or sealed in leak-proof outer bag | Single-bagging |
| Sharps | Blade or point covered with cap or blister pack | Exposed edge in poly-bag |
| Glass or fragile | Bubble wrap with 2-inch coverage all sides | Insufficient wrap thickness |
| Powders / granular | Sealed in poly-bag, then boxed | Bag without box |
| Sets (multi-unit) | “Sold as Set” or “Do Not Separate” sticker | Missing set sticker, units get split |
| Expiration-dated (grocery, supplements) | Expiration date visible on outer packaging, 105-day minimum shelf life at receiving | Date on inner packaging only |
| Adult products | Opaque black poly-bag | Transparent bag |
Category prep is where private-label sellers often assume the manufacturer handled it and don’t verify. Then a receiving associate flags 500 units for missing suffocation warnings and the prep fee eats a quarter of the launch margin. The safer default is inspecting a random sample of every incoming production run before shipping to FBA, or having the manufacturer photograph a sample unit for approval.
Once your prep is dialed in, the next lever is which SKUs are actually worth restocking, Amazon competitor analysis and reverse ASIN research help identify which listings have enough search demand to justify inventory investment in the first place.
When does a prep center beat self-prep on cost?
Prep centers charge per-unit fees to receive, inspect, label, bag, and forward inventory to FBA. Typical pricing:
| Service | Prep Center Range | Self-Prep Cost |
|---|---|---|
| Receive and inspect | $0.50 to $1.50 per unit | Labor + space |
| FNSKU labeling | $0.15 to $0.40 per unit | Label + printer |
| Poly-bagging | $0.30 to $0.75 per unit | Bag cost |
| Bubble wrap | $0.50 to $1.25 per unit | Wrap cost |
| Bundle / multi-pack | $1.00 to $2.50 per unit | Labor |
| Storage (per pallet/month) | $15 to $40 | Warehouse rent |
| Outbound shipment prep | $2.00 to $5.00 per carton | Labor |
Self-prep looks cheaper on paper because there’s no per-unit fee, but you’re paying in time and space. Prep a 500-unit shipment yourself and you’re looking at 6 to 10 hours of labeling and bagging, plus the cost of storing inventory until it’s ready to ship.
The break-even depends heavily on your local labor cost and available space. Roughly speaking, based on the cost ranges above and typical seller reports, many operations cross the point where a prep center makes sense somewhere in the several-hundred-units-per-month range. Above that, the time saved is usually worth the per-unit fees. Below it, self-prep or a virtual assistant handling prep often wins.
Prep centers also handle FBA rejections in reverse. If Amazon returns a shipment for prep failure, the center relabels or rebags and reships. Error rates at established prep centers are typically low, based on commonly cited prep center SLAs, though this varies by operator and should be verified before signing a contract. Not every “prep center” is equal, some are one-person garage operations, others are 50,000 square-foot facilities with warehouse management software. Ask for a facility tour or video walkthrough before committing.
If you’re deciding between FBA and self-fulfillment as your primary channel, the FBA vs FBM analysis covers the fulfillment side, while this post covers the prep side that both models eventually need. The /blog/ hub has more on FBA operations across the funnel.
What documentation reverses an unplanned prep fee?
Amazon charges unplanned prep fees automatically when receiving flags an issue. Reversing those charges requires evidence that either the prep was correct or the fee was misapplied.
The evidence Amazon actually accepts:
- Timestamped photos of the sealed carton before shipment. Show the outside of the carton, the shipping label, and a scale reading confirming weight.
- Timestamped photos of a random sample of units showing prep. FNSKU label visible, poly-bag sealed, warning text readable.
- Case pack photos. If shipping in case packs, photograph the case pack label and a cross-section showing units inside.
- Shipment plan reference. Compare the fee to your shipping plan, if Amazon charged for bubble-wrap prep on a SKU you flagged as not requiring it, that’s a straightforward reversal.
Open a case in Seller Central under “Fulfillment by Amazon > FBA inventory > Charged for unplanned services” and attach the photo evidence with unit counts. Reversal rates for well-documented cases are meaningfully higher than for cases relying on prose descriptions alone, based on seller community reporting, though outcomes depend on the specific fee type and reviewer.
The Amazon brand registry enrollment also unlocks more direct communication channels with Amazon support, which speeds fee-reversal cases for enrolled sellers. Watching prep-fee patterns across your account is part of the broader Amazon conversion rate and margin analysis every seller should run monthly, and pairs with listing optimization to protect both sides of the P&L.
This is research and operational guidance, not legal advice. Sellers facing large fee disputes or account-level enforcement should talk to a qualified Amazon consultant or attorney.
Frequently Asked Questions About FBA Prep Requirements
What happens if my FBA shipment fails prep at the warehouse?
Amazon can charge unplanned prep fees per unit, place the shipment in a receiving hold, or return the inventory at your cost. Fees vary by prep type but typically run $0.30 to $1.20 per unit for labeling and bagging. In some cases units are marked unfulfillable and you pay removal or disposal fees on top of the prep charge.
Do I need an FNSKU label if my product already has a UPC barcode?
Yes, unless the SKU is enrolled in Amazon’s Stickerless, Commingled inventory program. The FNSKU is Amazon’s internal barcode that ties a unit to your specific seller account. UPCs get shared across sellers, which is why default prep requires an FNSKU sticker covering the manufacturer barcode on the outside of the unit.
What size poly-bag suffocation warning does Amazon require?
Poly-bags with an opening 5 inches or larger (measured when flat) must carry a suffocation warning per current Seller Central guidance. The warning font must be at least 24-point for bags with total opening dimensions of 60 inches or more, and 10-point for smaller bags. The bag itself must be 1.5 mil thickness minimum and transparent.
Is it cheaper to use an Amazon prep center or do prep myself?
Self-prep is usually cheaper at low volume because you’re not paying labor. Prep centers become cost-effective once handling time exceeds what you or an employee can absorb, which for many sellers lands somewhere in the several-hundred-units-per-month range. The break-even depends on your local labor cost, storage space, and how you value your time.
Can I use my own SKU barcode instead of the FNSKU?
No. Amazon’s fulfillment system scans the FNSKU to route inventory to the right listing. Any other barcode visible on the outside of the unit, including UPC, EAN, or a private SKU, must be covered by the FNSKU sticker. Uncovered barcodes trigger rebag or relabel fees and can cause commingled inventory issues.
Conclusion
- FNSKU on every unit, over every other barcode, on a flat opaque surface. Non-negotiable outside Stickerless Commingled.
- Poly-bag specs: 1.5 mil minimum, transparent, sealed, suffocation warning at 5+ inch openings. Miss any of these and pay rebag fees.
- Carton limits are 50 lbs and 25 x 25 x 25 inches for standard. Team-lift and mechanical-lift labels exist for oversize but need advance approval.
- Category prep varies: liquids double-bag, sharps cap, glass wrap, sets sticker. Verify each production run.
- Prep centers scale better than self-prep above a few hundred units per month for most sellers. Below that, self-prep or a VA handling prep usually wins.
The prep side of FBA runs on rules; the demand side runs on data. Run your first ASIN through Keywords.am and see which search terms are worth stocking inventory against before the next production run.