How to Write FBA Prep Instructions for Your Manufacturer: Spec Sheet, Golden Sample, and Pre-Shipment Verification

Most private label sellers send prep requirements to their manufacturer in a WhatsApp message or a few lines of an email. The factory replies with a thumbs-up, and the seller assumes the problem is solved. Eight weeks later, a 2,000-unit shipment arrives at an Amazon fulfillment center with FNSKU labels placed over a box seam, or poly bags sealed on the wrong end, or labels missing altogether - and every single unit has the same defect. That is not a prep error. That is a replication event, and its cost is categorically different from anything that happens inside a prep facility.

Why Factory Prep Errors Are in a Different Cost Category

When a prep center makes a mistake, it typically affects the units currently on the table. A worker labels a batch incorrectly, someone catches it, the batch gets corrected before it ships. The blast radius is contained and the correction happens before the goods move.

Factory prep errors work differently. The factory sets up a workstation, trains a line worker on the prep task once, and then runs the entire production batch through that same setup. If the setup is wrong - wrong FNSKU applied, bag opening facing the wrong direction, label placed on a curved surface - every unit gets the same defect. The discovery point is not your factory. It is Amazon's inbound receiving dock, roughly eight to ten weeks after the goods were sealed into cartons and loaded onto a container.

Amazon discontinued all U.S. FBA prep and labeling services at the start of 2026, removing the warehouse-side backstop that previously caught supplier prep errors before units were counted into inventory. That backstop is gone. Units that arrive non-compliant now trigger unplanned prep fees - check Seller Central for current rates by unit size - or get rejected outright. For a seller with a 2,000-unit run, the difference between correct factory prep and incorrect factory prep is the difference between a profitable launch and a reprocessing bill that wipes the margin on the entire order.

Sellers who integrated documented, China-side prep with structured quality checks saw shipment rejection rates drop from roughly 12 percent to below 2 percent, according to case data published by Unicargo in 2026. The variable between those two outcomes was not the factory's skill level. It was whether the seller gave the factory a document precise enough to act on.

The Four Documents Your Supplier Needs Before Prep Starts

A supplier cannot prep correctly from memory or from a conversation. They need a file package they can print, pin to a workstation, and hand to a quality checker. That package has four components, and missing any one of them shifts the risk back onto you.

• The prep spec sheet. A single document covering every prep requirement for that SKU: label specifications, packaging specifications, carton specifications, and which barcodes must be covered. Version-numbered, with your company name and SKU at the top. This is the authoritative reference for every prep task on that order.
• FNSKU label files. The actual print-ready label files exported from Seller Central, in the exact format your factory's label printer accepts. Do not send a screenshot. Do not send a PDF that will be rescaled by the factory's print software. Send the source file with print dimensions locked, and confirm with the factory that the labels print at the correct physical size before production begins.
• Golden sample photos. A set of annotated photographs showing a correctly prepared unit from every relevant angle. These replace written placement descriptions, which factories routinely misinterpret. A photo with an arrow pointing to the label placement communicates more precisely than three sentences describing the same thing.
• Written approval sign-off form. A one-page document the factory signs before production resumes, confirming they have received the spec sheet, reproduced the golden sample, and understand the inspection criteria. Simple, but it creates a documented handoff that protects you if a dispute arises later.

Version control on the spec sheet matters. If you change the FNSKU for a second production run, the old spec sheet must not survive on the factory floor. Put a version number in the filename and in the document header. When you send an update, explicitly instruct the factory to discard the previous version and confirm receipt of the new one in writing.

Unit-Level Spec: FNSKU Label Dimensions, DPI, Placement, and Barcode Coverage

The label section of your spec sheet needs to be precise enough that a factory worker with no FBA knowledge can execute it correctly on the first attempt. Instructions like "place the barcode on the front" will produce incorrect results.

Label specifications

Amazon specifies minimum and maximum physical dimensions for FNSKU labels - check Seller Central's prep requirements for current figures, as these apply to every unit regardless of product size. Labels must be printed at a minimum resolution (Amazon specifies a DPI floor in their documentation) in Code 128A barcode format on white, non-reflective adhesive paper. Glossy label stock is not acceptable. Thermal-transfer printing on matte stock is the standard that survives ocean freight; direct thermal labels can smear in the humidity of a container crossing the Pacific, making them unreadable at Amazon's receiving dock.

Amazon also requires a clear quiet zone - an unprinted margin - around the barcode on all four sides, with wider clearance on the left and right than on the top and bottom. Your spec sheet should include a dimensioned diagram showing the quiet zone, not just a written description of it. Replicate this diagram in your golden sample photos with an annotation callout.

Placement rules

• The label must sit on a flat surface - never on a seam, curve, corner, or folded edge. A label that bridges a seam will partially tear when the package is opened, and a label on a curve will not lie flat enough to scan reliably.
• Amazon sets a minimum clearance between the label edge and any package edge - check Seller Central for the current requirement and state it in your spec sheet with a measurement arrow on the golden sample photo showing exactly where the label sits.
• Every other scannable barcode on the unit must be fully covered so it cannot be scanned at Amazon's receiving dock. Manufacturer UPC, EAN, or any retail barcode visible through the product packaging must be covered with an opaque label, with no gaps around the edges of the covering sticker.

That last point produces one of the most common factory errors. A line worker sees a UPC printed on the product or inner carton and assumes covering it is optional. It is not. Any competing barcode that scans at receiving will cause the unit to be received against the wrong ASIN, which can mean your inventory is counted into a different seller's listing.

Packaging Spec: Poly Bags, Seal Method, Suffocation Warnings, and Scannability

If your product requires poly bagging, the packaging section of your spec sheet must cover five separate variables. Getting any one of them wrong will either trigger a prep rejection or create a safety compliance issue that Amazon takes seriously.

Bag specifications

• Thickness. Amazon sets a minimum bag thickness - check Seller Central for the current figure. Bags thinner than the minimum are rejected at receiving. Include the thickness specification in your spec sheet and ask your factory to provide the bag supplier's spec sheet as written evidence of compliance before bagging begins.
• Transparency. The bag must be fully transparent. Tinted, frosted, or heavily printed bags that obscure the product are not compliant, even if the FNSKU is visible.
• Seal. The bag must be completely sealed with no open tops or fold-and-tuck closures. Heat seal or self-seal with a permanent adhesive strip are both acceptable; specify which method your factory should use and confirm the equipment is available before production starts.
• Length. The bag may not be more than a certain length beyond the product it contains - Amazon specifies this as a maximum overage, which you can find in Seller Central's packaging requirements. A bag that balloons out well beyond the product suggests the wrong bag size was selected.
• Scannability. The FNSKU must be scannable through the sealed bag without opening it. Test this with a barcode scanner app before approving the golden sample. If the label is placed inside the bag, the bag material and print on the bag must not interfere with the scan.

Suffocation warnings

Any poly bag with an opening above a certain diameter requires a printed suffocation warning on the outside. Amazon specifies the threshold opening size and the required minimum font size, which increases as the bag gets larger - check Seller Central for the current size thresholds and font minimums. The exact warning text and font size for your bag dimensions must appear verbatim on your spec sheet, and the golden sample must show the warning in the correct position on the correct surface of the bag. Factories that use pre-printed bags from a supplier sometimes receive bags without the required warning; confirm this before accepting any bag stock.

Carton-Level Spec: Weight and Dimension Limits, Label Placement, Team Lift Markings

Your carton spec section covers the master carton that leaves the factory, not the retail unit packaging. These requirements affect whether Amazon accepts the inbound shipment and whether freight handlers can move cartons safely.

Amazon sets a maximum weight and a maximum dimension for any single side of a master carton - check Seller Central's inbound requirements for current figures. Plan your carton configuration during the ordering process, before the factory builds cartons to the wrong size. A carton that is too heavy or too large does not get a variance; it gets returned or refused.

FBA shipment ID labels must be placed with a minimum clearance from any box edge and never over the opening seam of the carton. A label placed on a seam tears when the carton is opened and becomes unreadable at receiving. Specify the placement zone on a diagram - centered on the top panel or a side panel, with clearance measurements shown - and include that diagram in your spec sheet.

Cartons above a certain weight threshold require Team Lift or Heavy Package warning labels on all five surfaces: top, bottom, and all four sides. Check Amazon's current weight threshold and note it in your spec sheet with a clear statement of which surfaces require the label. Factories that regularly ship heavy goods often have these labels on hand; confirm availability before the production run ends so there is no last-minute scramble.

One common carton-label failure mode deserves specific mention: thermal-printed labels that smear in humidity during ocean transit. Test any label the factory applies by rubbing it with a damp cloth before approving the pre-shipment sample. A label that smears in that test will smear in a container on a six-week ocean crossing.

The Golden Sample Kit: What to Include, How to Photograph It, and the Approval Workflow

A golden sample is a single completed, fully prepped unit - labeled, bagged, and ready for FBA - that the factory produces and photographs before the full production run proceeds. It is the physical proof that the factory understood your spec sheet correctly, and it becomes the reference standard for every subsequent order of that SKU.

What the golden sample photos must show

• Front face with FNSKU label visible. Annotate the photo to show the label boundaries, the quiet zone margins, and the clearance from the nearest package edge. The annotation can be done in any image editor - arrows and callout text are sufficient. The factory should add these annotations themselves, not just send an unmarked photo.
• Close-up of the FNSKU barcode. Zoomed in enough that the quiet zone is visible on all sides and the label material is identifiable as matte stock. This angle catches glossy paper substitutions and insufficient quiet zone clearance before 2,000 units are labeled.
• All visible sides of the unit showing covered barcodes. Every original manufacturer barcode that has been covered should appear in this shot, with the covering label clearly in place and no visible gaps at the edges.
• Exterior of any secondary packaging. For poly-bagged units, the shot must show the sealed edge, the suffocation warning in place on the correct surface, and the FNSKU visible through the bag material without the bag being opened.

The approval workflow

1. Send the spec sheet and FNSKU print files to the factory, along with a blank annotation template for the photos.
2. Factory preps a single unit following the spec sheet - one unit only, before any production batch begins.
3. Factory photographs the unit from all required angles and adds annotation callouts to each photo, marking label placement, quiet zones, and covered barcodes.
4. Factory emails the annotated photo set to you or your QC contact, along with the completed sign-off form for review.
5. Compare each photo against the spec sheet requirements, checking label dimensions, placement clearance, barcode coverage, bag seal, and suffocation warning.
6. Sign and return the approval form if the unit passes - or document the specific corrections needed and request a new sample unit before production continues.

The golden sample photos become a permanent attachment to the spec sheet for that SKU. When a new factory produces the same product, they receive the same golden sample photos as the target standard. When a QC inspector checks the pre-shipment sample, they compare against the same photos. The photos create a visual chain of custody that written specs alone cannot provide.

One correctly prepared golden sample, approved before a single production unit is prepped, costs near zero. Reprocessing thousands of units at a U.S. prep center to correct a replicating factory error costs real money and delays a launch by weeks.

First Article Inspection: The Pre-Production Sign-Off That Stops Errors Before They Replicate

First article inspection for prep purposes is separate from a product quality inspection. It is a deliberate checkpoint at which you or your QC partner signs off on a single completed, prepped unit before the factory continues prepping the rest of the batch. Many sellers who run thorough product QC inspections skip this step entirely - and then discover prep errors at scale.

The timing is everything. If the factory preps 200 units before you inspect, you may discover an error that requires reprocessing 200 units. If the factory preps one unit and pauses for sign-off, correction costs nothing - the worker re-labels, re-bags, or adjusts the workstation setup before running the full batch. Correction at this stage approaches zero cost; correction at a U.S. prep center after a full production run is priced per unit, multiplied by every unit in the shipment.

A first article prep inspection covers a specific checklist, entirely separate from product quality:

• FNSKU barcode scans correctly and the scan result matches the intended ASIN - test this with an actual barcode scanner, not visual inspection
• Label sits on a flat surface with correct clearance from all edges, matching the golden sample annotation
• All competing barcodes are covered with no scannable gaps around the covering label edges
• Poly bag (if applicable) is correct thickness, completely sealed, and FNSKU is scannable through the bag
• Suffocation warning is present, correctly sized for the bag dimensions, and on the correct surface
• Carton FBA label placement and Team Lift markings are correct and on the right surfaces

The sign-off form records the date, SKU, FNSKU number, the inspector's name, and confirmation that the unit matches the golden sample. The factory keeps a copy. You keep a copy. If a dispute arises later about prep quality, the sign-off establishes the documented checkpoint and the party responsible for authorizing the production run to continue.

Pre-Shipment Verification Checklist: What to Confirm Before Cartons Are Sealed

The pre-shipment check happens after the production run is complete and before cartons are taped shut and loaded onto the freight. This is the last practical point at which errors can be corrected without routing goods through a U.S. prep center. Pull a sample from multiple cartons - not just the first carton packed - because prep quality sometimes degrades midway through a large batch as workers tire or supplies run low.

For each sampled unit, verify the following before approving the shipment:

• FNSKU barcode scans to the correct ASIN using a standard barcode scanner app - not a visual check
• Label placement matches the golden sample annotation exactly: flat surface, correct clearance from edges, not on any seam or curve
• All manufacturer barcodes are covered with no visible gaps at the edges of the covering label
• Poly bags are fully sealed with no open edges, within the correct length range, and FNSKU is scannable through the bag
• Suffocation warnings are present and correctly sized on all bags that require them
• A filled carton (not an empty one) has been weighed and measured and falls within Amazon's inbound limits
• FBA shipment ID labels are on the correct carton panel with correct clearance from edges, not on any seam
• Team Lift labels appear on all five surfaces of any carton above the weight threshold
• Thermal-printed labels pass the damp cloth smear test before cartons are loaded

Document the sample check with photos that include the carton number in frame. A photo showing a correctly placed label alongside the visible carton number is evidence; a photo of a correctly placed label with no identifiable carton context is not. If a third-party inspection company runs this check, their written report with photos becomes part of the shipment file.

When Factory Prep Is the Right Call and When to Route Through a Prep Center

Factory prep costs less per unit than routing through a U.S. prep center - check current prep center rates for comparison, as pricing varies by service type and volume - but it carries higher quality risk because errors are invisible for months. The right choice depends on the complexity of the prep task, the history with the factory, and how much risk a particular order can absorb.

Scenario	Factory prep	Prep center
Simple labeling, no bagging	Suitable with spec sheet and golden sample in place	Adds cost without proportionate risk reduction
Complex bundling or kitting	Higher risk; factory may misread bundle rules	Preferred - prep centers are built for this work
New factory, first run	Higher risk without established QC relationship	Consider splitting: factory labels, prep center verifies
Established factory with signed spec sheets	Suitable with first article inspection documented	Redundant if the QC process is already proven
Time-sensitive launch	Faster if factory prep is already qualified	Adds domestic transit leg, extends timeline
Known prep errors already shipped	Not applicable - goods are already in transit	Route to prep center before Amazon receiving

The practical approach many experienced sellers use: route the first run of any new SKU through a prep center to establish the golden sample baseline and verify Amazon receives it cleanly, then transition to factory prep for subsequent runs once the process is proven. This costs more on the first order but creates a verified reference standard that eliminates guesswork on every order that follows. If a production run has already shipped with known prep issues, routing to a prep center before Amazon receiving avoids inbound defect fees and prevents inventory from being held or refused at the fulfillment center.

Frequently Asked Questions

What happens if my factory applies the wrong FNSKU to 2,000 units?

Every unit receives the wrong FNSKU, and the goods will either be received into inventory against the wrong ASIN or rejected at Amazon's inbound dock. Correction requires a relabel of every unit, either at a U.S. prep center before Amazon receiving or through an Amazon-approved reprocessing service after the fact. Either route costs significantly more than getting the label correct at the factory, and the delay typically pushes a launch back by several weeks.

Do I need a new golden sample every time I place a reorder from the same factory?

Not for identical reorders using the same spec sheet version and the same FNSKU. A new golden sample is required when the FNSKU changes, the packaging changes, you switch factories, or a significant amount of time has passed since the last qualified run - factory personnel turn over, and the worker who understood your spec sheet may no longer be there. When in doubt on a reorder, request a first article inspection photo rather than a full new golden sample; it is faster and still creates a documented checkpoint before the batch proceeds.

Can my factory source poly bags and labels themselves, or do I need to send materials?

Factories can source their own materials if you specify the exact requirements in writing and confirm the factory's supplier can meet them. The risk is substitution - a slightly thinner bag, glossy label stock, or a bag without a suffocation warning printed. For labels specifically, sending pre-printed FNSKU labels from a verified source eliminates the risk of the factory printing incorrect labels or using non-compliant stock. For bags, require the factory to provide the bag supplier's spec sheet before bagging begins, not after a shipment fails an inspection.

What should a prep spec sheet look like as a document - what sections does it need?

A working prep spec sheet for a factory has six sections: product identification (SKU, FNSKU, ASIN, and spec version number at the top), unit label requirements (dimensions, DPI, format, material, placement coordinates with a diagram), barcode coverage requirements (which barcodes to cover and how), packaging requirements (bag specs, seal method, suffocation warning text), carton requirements (weight and dimension limits, label placement diagram, Team Lift instructions), and a sign-off block for the factory supervisor. Attach the FNSKU print file and golden sample photos as numbered exhibits referenced in the document body. Keep the language direct; write it for a line supervisor, not an Amazon seller.

If I use a third-party inspection company for pre-shipment checks, do I still need a spec sheet for the factory?

Yes. The inspection company checks against your spec sheet - without it, they have no standard to inspect against. An inspector who discovers a prep error at the pre-shipment stage is extremely valuable, but the root correction is ensuring the factory received unambiguous instructions before prep started. The inspection is a verification layer, not a substitute for the spec document. If the inspector finds errors and the factory has no signed spec sheet on file, there is also no documented basis for holding the factory accountable for reprocessing costs.

Is a China-based third-party prep center a better option than factory prep?

China-based prep centers offer a middle path: lower cost than U.S. prep, with the quality control separation of a dedicated facility that does nothing but prep. The tradeoff is adding a logistics step and another coordination party between the factory and your freight forwarder. For sellers whose factories have unreliable prep quality but who are not ready to absorb U.S. prep center pricing, a China-side prep facility can be the right call. For sellers with a well-documented factory prep process, a signed spec sheet, and first article inspection in place, the additional step adds cost and transit time without proportionate benefit.