FBA prep is the work of getting your inventory ready to meet Amazon's requirements before it reaches a fulfillment center. That means the right labels, the right packaging, and the right handling for each product type. Amazon inspects inbound shipments, and units that arrive out of spec get consequences: unplanned prep fees billed back to you, labeling charges, delayed check-in, or in the worst case a rejected shipment returned at your expense.
None of the rules are complicated on their own. The trouble is that there are a lot of them, they change by category, and one missed FNSKU or one missing suffocation warning can hold up a whole shipment. This guide walks through what Amazon requires, where sellers get flagged, and when it makes sense to hand prep to a prep center instead of doing it yourself.
What Amazon requires before your inventory ships
Every unit going into FBA has to be scannable, protected, and identifiable at the fulfillment center. Amazon's inbound rules come down to a few things working together. Each unit needs a scannable barcode that maps to your listing. Fragile, loose, or leaking products need packaging that survives the trip and protects the units around them. And expiration-dated, adult, or regulated goods have extra rules layered on top.
Amazon assumes you have done this before the box arrives. There is no prep step waiting for you at the fulfillment center unless you enroll in and pay for FBA Prep Service, and their per-unit fees are higher than most sellers expect. Getting it right up front is what keeps your cost per unit down and your check-in fast.
- A scannable FNSKU or manufacturer barcode on every unit, with no other scannable barcode exposed
- Packaging appropriate to the product: polybags, bubble wrap, boxes, or sets taped and labeled as one unit
- Expiration dates printed and formatted to Amazon's standard where they apply
- Compliant handling and documentation for any hazmat or regulated item
FNSKU labeling requirements
The FNSKU is the barcode Amazon uses to tie a physical unit to your specific listing and inventory. It is the single most common thing sellers get wrong, and it is the easiest to get flagged on because a scanner either reads it or it does not.
When a label is required
Most units need an FNSKU label. The exception is stickerless commingled inventory, where Amazon uses the manufacturer barcode and pools your units with other sellers' identical items. Most sellers avoid commingled inventory because you lose control over which physical unit ships to your customer. If you are running private label, bundles, or anything where condition matters, you want a unique FNSKU on every unit.
Label placement and legibility
The label has to scan on the first try. Place it on a flat surface, not wrapping around a corner or a curved edge where the bars distort. Keep it clear of seams, tape, and box edges. Print at 300 DPI or better on a thermal or laser printer, since a smudged or low-resolution label is treated the same as no label. Thermal labels should use direct thermal stock rated to hold up in a warehouse without fading.
Covering existing barcodes
If the product already has a UPC, EAN, or manufacturer barcode on the packaging, that barcode has to be fully covered so the fulfillment center scanner reads only your FNSKU. A unit with two scannable barcodes creates a conflict that can route your inventory to the wrong listing or another seller's stock. Cover the original completely, or apply the FNSKU directly over it.
Polybag requirements
Polybagging protects units and keeps loose or soft goods together, but Amazon has specific rules about when a bag is required and how it has to be finished.
The suffocation warning rule
Any polybag with an opening of 5 inches or larger, measured flat, must carry a printed suffocation warning. The warning has to be legible and either printed on the bag or applied as a label. This is one of the most common reasons soft-goods shipments get flagged, because sellers bag a product correctly and forget the warning text. The warning is required regardless of whether the end product is intended for children.
When a polybag is required
Amazon requires a polybag for units that would be damaged, soiled, or separated without one. That covers apparel and soft goods, products with loose parts, and items where the manufacturer packaging is not a durable retail box. The bag protects the unit from dust and moisture in the fulfillment center and keeps multi-part items from coming apart on the line.
Sizing and sealing
Use a bag sized close to the product. Excess film adds bulk and can hide the barcode. Amazon requires transparent bags of at least 1.5 mil thickness so units are visible and the bag does not tear in handling. Seal the bag completely, since an open bag does not count as bagged. The FNSKU label goes on the outside of the bag, not on the product inside where a scanner cannot reach it.
Packaging by product type
Beyond labels and bags, Amazon's packaging rules change with what you are shipping. These are the categories where prep mistakes cluster.
Apparel and shoes
Clothing, fabric, and textile products have to be polybagged with a suffocation warning to protect them from dirt and moisture. Shoes ship in a box or a polybag that fully covers the pair, with no shoe surface exposed. Boxed shoes still need the outer box protected if it doubles as the retail package, since a scuffed shoe box gets treated as a damaged unit.
Fragile items
Glass, ceramics, and other breakables need to survive a 3-foot drop test inside their packaging. Wrap each unit with enough bubble wrap or protective material that it does not shift, and use a rigid box rather than a bag. If two fragile units ship together, they each need enough cushioning that they cannot knock into one another.
Sets and bundles
Products sold as a set have to be labeled and packaged so they stay together as one unit. Mark the packaging "Sold as set" or "Do not separate" and apply a single FNSKU to the whole bundle, not to the individual pieces. If a fulfillment center associate can pull one item out of your set, Amazon can break the bundle and your customer receives a partial order.
Oversized items
Oversized and heavy units have their own handling rules and often need team-lift or additional labeling. Units over 50 pounds require a team-lift label, and units over 100 pounds require a mechanical-lift label. Packaging has to hold the weight without collapsing, since a box that fails in transit damages everything near it and can flag the whole shipment.
Hazmat and regulated products
Hazmat is where most prep centers stop. Batteries, aerosols, flammables, cleaning chemicals, and many health and beauty products are regulated, and handling them wrong is a safety and legal problem rather than a flagged listing. Most prep centers turn this work away, which leaves sellers of regulated products without good options.
This is where Dispatch is different. We are hazmat certified to DOT 49 CFR and IMDG 172, so we can classify, document, package, and label regulated shipments to standard rather than sending them back to you. That covers the paperwork most sellers do not want to touch and the compliant packaging that keeps these shipments moving. If you sell regulated products and have struggled to find a prep center that will take them, get in touch and we will walk through your catalog.
Amazon also has its own dangerous-goods program, and a product classified as hazmat has to clear Amazon's review before it can ship into FBA. Getting the classification and documentation right the first time is what keeps a regulated product from sitting in limbo.
Common reasons FBA shipments get flagged
Most problems trace back to a short list of mistakes. If a shipment gets held, charged, or returned, it is usually one of these.
- An unreadable, missing, or wrong FNSKU label
- A second scannable barcode left exposed next to the FNSKU
- A polybag over 5 inches with no suffocation warning
- Loose sets that can be separated at the fulfillment center
- Fragile units that fail the drop test and arrive broken
- Expiration dates missing or in the wrong format on dated goods
- A regulated item shipped without hazmat classification or paperwork
Each of these is avoidable with a consistent prep process. The cost of getting it wrong is not just the fee. A flagged shipment delays your inventory going live, which means lost sales days and a hit to your rank while you sort it out.
When to use a prep center instead of prepping yourself
Prepping yourself works at low volume. Once you are moving hundreds or thousands of units a month, the math changes. Prep is repetitive, space-hungry work, and every hour you spend polybagging is an hour you are not spending on sourcing or marketing. A prep center turns that fixed time cost into a predictable per-unit cost you can price into your margins. You can see how that per-unit pricing works on our pricing page.
A prep center also absorbs the rule changes for you. When Amazon updates a labeling or packaging requirement, that is our job to track, not yours. And for anything specialized, such as hazmat, fragile goods, or large bundles, a center that handles it daily gets it right more consistently than an occasional in-house effort.
The clearest signal it is time is when prep is capping your growth. If you are turning down inventory because you cannot prep it fast enough, or eating Amazon prep fees because units slip through out of spec, a prep center pays for itself. If you want to see what your volume would cost, get an instant estimate and we will show you real numbers.
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