We inspect prep work for sellers who come to us after a rejection, and the pattern is remarkably consistent: it's almost never a new or exotic problem. It's one of the same nine mistakes, over and over, made by sellers who didn't know the rule existed or skipped a step to save ten minutes on pack-out day. Here's the full list, why Amazon's receiving centers catch each one, and the exact fix.
Nine mistakes cause most Amazon FBA shipment rejections: FNSKU labeling errors, poly bag violations, undeclared hazmat, bundle mislabeling, box weight/dimension mismatches, case-pack count errors, missing expiration date labels, incorrect prep category assignment, and shipping without required suffocation warnings. A written prep checklist run on every unit typically brings rejection rates from 3–8% down to under 1%.
A Rejected Shipment Costs More Than the Delay
A single rejected case doesn't just sit in limbo. It triggers a return-to-sender cycle: the prep center or the seller has to receive it back, figure out what went wrong, fix it, and re-ship it, usually five to ten days after the original ship date. Meanwhile the SKU is out of stock on Amazon, losing sales velocity and Buy Box position while a competitor's listing climbs.
On a 1,000-unit shipment at an 8 percent rejection rate, that's 80 units cycling back through prep before they ever have a chance to earn a sale. The nine mistakes below account for nearly all of it.
The 9 Mistakes, and the Fix for Each
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1. FNSKU labels that don't scan
The most common single cause of rejection. A label printed at low resolution, placed over a curve where the scanner can't read it, or applied without fully covering the manufacturer's original barcode. Fix: scan-test every FNSKU label before sealing the case, and always cover the original barcode completely rather than placing the FNSKU beside it.
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2. Poly bag suffocation warning violations
Any bag with a 5-inch or larger opening, or 1 quart or larger in volume, needs a printed suffocation warning in the correct font size. Missing it, printing it too small, or using a bag that's clearly too loose for the item all trigger a hold. Fix: standardize on pre-printed compliant poly bags sized correctly for each SKU rather than sourcing generic bags and adding warnings after the fact.
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3. Undeclared hazmat
Lithium batteries, aerosols, flammables, and anything requiring an MSDS need hazmat review and approval in Seller Central before they ship. An undeclared hazardous item can get the entire pallet quarantined, not just the offending case. Fix: confirm hazmat status and approval status for every SKU before the first unit is packed, not after the shipment plan is created.
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4. Bundle mislabeling
Shipping components that are meant to sell together as loose units, without bundle registration in Seller Central and a "Sold as Set" label or shrink wrap holding them together, reads to Amazon's receiving system as mis-shipped inventory. Fix: register the bundle SKU first, then physically secure components so they can't separate anywhere between your dock and the FBA shelf.
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5. Box weight and dimension mismatches
Estimating carton weight and size instead of measuring the actual packed box causes a mismatch with the shipment plan, which triggers manual verification and delay. Fix: weigh and measure a sample of actual sealed cartons, not the empty box or the spec sheet, before entering numbers into the shipment plan.
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6. Case-pack count errors
A case marked as 24 units that actually contains 20 or 30 gets flagged during Amazon's count-and-verify step. This is almost always a manual counting mistake at pack-out. Fix: scan-and-count each case before sealing rather than relying on a visual count or a standard fill assumption.
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7. Missing or unreadable expiration date labels
Products with a shelf life need a legible, correctly placed expiration date, typically MM/DD/YYYY. Handwritten dates, smudged ink, or a date hidden under another label are frequent rejection triggers. Fix: use a printed label in the placement location Amazon specifies for the category, never handwritten.
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8. Wrong prep category assignment
Every SKU has a specific required prep type in Seller Central (poly bagging, bubble wrap, box prep, none). Shipping a unit prepped for the wrong category, commonly under-prepping a fragile item that actually requires bubble wrap, causes a hold. Fix: confirm the exact prep type required per SKU in Seller Central before the first production run, and re-check after any packaging change.
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9. Shipping without required protective packaging
Fragile items without adequate bubble wrap or void fill arrive damaged, and damaged inventory gets refused at receiving rather than accepted and written off. Fix: match void fill and cushioning to the item's fragility rating, not to what's cheapest per unit, since a rejected shipment costs more than the extra bubble wrap ever would.
These Mistakes Get More Expensive During Q4
A rejected case that would normally cycle back in 5 to 10 days can take 2 to 3 weeks during Q4, when every prep center's queue is backed up.
A rejection in early November can mean the SKU never makes it onto the FBA shelf before Black Friday, the highest-velocity week of the year.
Sellers racing to hit inbound deadlines skip QA steps to save time, which increases the exact mistakes on this list.
Repeated rejections can affect Amazon's view of your inventory performance metrics, which factor into storage limits and account standing.
If you're prepping in-house and heading into a high-volume season, running this checklist against a sample case from every batch, not just the first one, catches drift before it becomes a pattern. For the full month-by-month Q4 prep timeline, see our peak season fulfillment guide.
Why This Checklist Is Easier to Run at a Prep Center Than In-House
Every mistake above has a simple individual fix. The hard part isn't knowing the rule, it's running the same checklist on unit five hundred of a shift with the same discipline as unit one. That's the actual difference between a 5 percent rejection rate and a 0.5 percent rejection rate: not knowledge, but a repeatable QA step built into the workflow instead of relying on someone remembering.
An experienced prep center runs a scan-test, a visual poly bag check, and a weight verification on every case as a standard part of the line, not an extra step someone has to remember to add. That structural difference is why prep centers with real QA processes consistently post rejection rates under 1 percent while sellers doing ad hoc in-house prep land in the 3 to 8 percent range, even when everyone involved knows the rules.
Frequently Asked Questions
FNSKU labeling errors are the single most common cause: a wrong barcode, a label placed where a scanner can't read it, or a label applied over an existing manufacturer barcode instead of covering it completely. Amazon's receiving centers scan every unit, and a label that doesn't scan cleanly gets the whole case flagged.
Any poly bag with a 5-inch or larger opening requires a suffocation warning printed in the correct font size, and any bag with a 1-quart or larger volume needs the warning regardless of opening size. Amazon rejects bags that are missing the warning, have it printed too small to read, or use bags that are visibly too loose for the product inside.
Only if it's registered as a bundle SKU in Seller Central and physically labeled "Sold as Set" or shrink-wrapped so components can't separate in the warehouse. Shipping loose items that are meant to sell together, without bundle registration and a single FNSKU, gets the shipment flagged as mis-shipped units rather than a bundle.
Undeclared hazmat (lithium batteries, aerosols, flammables, anything with an MSDS requirement) is one of the fastest ways to get an entire shipment held, not just the case. Amazon requires a hazmat review and approval in Seller Central before the SKU ships, and receiving centers that catch an undeclared hazardous item will quarantine the pallet pending an internal safety review.
When the actual weight or dimensions of a carton don't match what was entered in the shipment plan, Amazon's automated receiving systems flag the discrepancy and can hold the case for manual verification, which adds days. This usually happens when a seller estimates box specs instead of weighing and measuring the actual packed carton.
Run every unit through a written prep checklist before it ships: correct FNSKU scan test, poly bag compliance check, hazmat declaration status, carton weight and dimension verification, expiration date sticker placement where required, and case-pack accuracy against the shipment plan. Most sellers who outsource to an experienced prep center see rejection rates drop to under 1 percent because the checklist runs on every unit, not just when someone remembers.
A well-run prep operation, in-house or outsourced, should keep rejections under 1 percent of units shipped. Sellers doing their own prep without a formal checklist commonly see 3 to 8 percent rejection rates in their first year, concentrated in FNSKU errors and poly bag violations.
Amazon itself doesn't charge a direct rejection fee in most cases, but the real cost is indirect: the prep center's return-to-sender or re-prep fee (typically $0.30 to $0.60 per unit), the shipping cost to send it back, the delay in the item hitting the FBA shelf, and lost sales velocity while the SKU is out of stock. On a 1,000-unit shipment with an 8 percent rejection rate, that's 80 units cycling through re-prep before they ever earn a sale.
Any product with a shelf life needs a legible expiration date printed or affixed in a consistent, scannable location, typically MM/DD/YYYY format, following Amazon's specific placement guidelines for the category. Handwritten or smudged dates, and dates hidden under other labeling, are common rejection triggers.
If you're shipping fewer than a few hundred units a month and have the time to build and follow a strict prep checklist yourself, in-house can work. Once volume grows or you're managing multiple SKUs with different prep requirements, an experienced prep center's built-in QA process almost always pays for itself in avoided rejections, faster FBA-shelf time, and fewer hours spent troubleshooting Seller Central holds.
If the shipment plan says a case contains 24 units and the actual case has 20 or 30, Amazon's receiving process flags the discrepancy during the count-and-verify step. This is usually a manual counting error at pack-out, and it's one of the easiest mistakes to prevent with a simple scan-and-count step before sealing each case.
Amazon prohibits shipping units in loose retail blister packs without additional protection, using bags without suffocation warnings where required, using unsealed poly bags, and using cartons that don't meet Amazon's minimum strength requirements for the product weight. Category-specific rules add further restrictions, so checking the current FBA packaging requirements for your specific product category before packing is worth the ten minutes it takes.
Tired of chasing down FBA rejections?
Simple Distribution runs a scan-and-verify QA step on every unit that leaves our dock. Sub-1% rejection rate, 24 to 48 hour turnaround, and a geographic edge shipping into Amazon's southeastern fulfillment network.