A Coupang Fulfillment Center Rejected 1,200 Units Because the Barcodes Would Not Scan
Barcode and Label Scan Verification Guide - Why Barcodes Fail to Scan, EAN-13, ITF-14 and Code 128 Compared, Print Size, Quiet Zone, Color Contrast and Print Quality Grade Standards, Spec Sheet Items, Stage-by-Stage Checks and a Checklist

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A Korean kitchenware brand produced 4,800 food storage container sets at a plastics factory in Ningbo, Zhejiang. The pre-shipment inspection passed on appearance and quantity. But when the goods arrived at a Coupang Rocket Growth fulfillment center, about 1,200 units were rejected at receiving because "the product barcode does not scan." The brand had to rent separate warehouse space, relabel and resubmit the goods, losing two weeks. Meanwhile the listing showed out of stock and its search ranking dropped.

Tracing the cause turned up several overlapping problems. The factory had shrunk the barcode from the design file to 70% to fit the side of the box. The box was uncoated kraft board, so black bars printed on a brown background had low contrast. On some boxes, shrink film covered the barcode and reflected light, and some boxes had the barcode stickers for two color options swapped. The inspector had only scanned a few units with a smartphone app and recorded them as "readable."

A barcode can look perfectly fine to the eye, but if the fulfillment center scanner cannot read it, the product does not even get received. This article starts with why barcodes fail to scan, then covers which barcode to use for each packaging level, how to set size, quiet zone, color contrast and print quality grade in numbers, and what to check in the spec sheet and at inspection.

A reply of "barcodes printed" is not enough. Set the barcode-to-SKU mapping table, print magnification, quiet zone, colors and print quality grade in numbers, and get verifier results from the first production print run. That is how you prevent receiving rejections.

1. Why a Barcode That Looks Fine Will Not Scan

A barcode scanner reads the widths of bars and spaces from the amount of reflected light. Even if a barcode looks sharp to the eye, a scanner cannot read it if the widths are slightly off or the contrast is low. These are the causes we see most often in products from Chinese factories.

• Reduced print size: The factory shrinks the barcode on its own to fit the box or label. Shrink an EAN-13 below 80% of nominal size and the bars become so thin they are vulnerable to ink spread. Cutting only the height (truncation) is another common mistake.
• Poor color contrast: Most scanners use red light (660nm). Red or orange bars look like background to the scanner, and kraft or dark backgrounds are hard to tell apart from the bars.
• Insufficient quiet zone: If borders, text or design elements intrude on the blank space required on either side of the barcode, the scanner cannot find the start and end.
• Ink spread and fading: Flexo printing on corrugated board tends to spread ink and thicken the bars, and direct thermal labels fade with heat and sunlight.
• Placement: Labels placed on box edges, folding panels, curved containers or under shrink film get bent or reflect light.
• Number errors: A wrong check digit, another SKU's barcode, or a random number not registered with GS1. In this case the barcode scans but registers as the wrong product, which is even more dangerous.

A scan test alone will not catch that last cause. Whether a barcode reads and whether it reads as the right product have to be checked separately. For labeling requirements in general, see Episode 46, and for packaging specs, Episode 15.

2. Barcode Types — Which One Goes Where

Barcode types differ by where they go and who reads them. If you only tell the factory "please add a barcode," it will pick whatever type it likes, so decide first which barcode each packaging level uses.

Get Your Numbers from GS1

EAN-13 numbers should be built from a company prefix you receive by joining an organization such as GS1 Korea. Random numbers from the factory or bought online can collide with other companies' products, and channels such as Coupang and Amazon sometimes check against the GS1 database and refuse registration. Once you have your numbers, build a mapping table of barcode numbers by SKU and share it with the factory.

Unit Barcodes and Carton Barcodes Are Different

If you put the unit EAN-13 on the master carton as is, the fulfillment center may receive one carton as one unit. Use ITF-14 or the carton label specified by the channel on master cartons, and change the number when the case pack quantity changes. Mismatches between case pack quantity and carton markings are covered in Episode 116.

3. Print Quality Standards — What to Set in Numbers

Barcode quality is graded, not judged as simply "reads" or "does not read." A verifier built to ISO/IEC 15416 measures contrast, bar width deviation, defects and more, and assigns a grade from A to F. GS1 recommends 1.5/06/660, or grade C or better, for retail barcodes, and large retailers sometimes demand a higher grade.

Smartphone barcode apps often get there in the end by zooming in and retrying several times. Fixed and handheld scanners at fulfillment centers have to read fast on the first try, so the bar is much higher. Reading in an app alone should never count as a pass.

4. Items to Include in the Spec Sheet

With a single line like "print barcode," every factory picks its own size and position. Put the items below into a table and attach it to your spec sheet or packing instructions. For spec sheets, see Episode 59.

Be sure to send the original design files as well. If the factory captures an image and redraws the barcode or resizes it, the bar widths shift slightly. Send barcodes as vector files (AI, PDF) and add "do not change size or proportions."

5. How to Check at Each Stage

Design and Sample Stage

Measure the barcode size on the print proof (PDF) the factory sends, and confirm that the digits under the barcode match the number in your mapping table. When you receive physical sample boxes, scan them with a handheld scanner and, if possible, grade them with a verifier. If the product needs a channel label, check now that the label size and position match the channel's guide. For Amazon receiving label requirements, see Episode 16.

Production Stage

Get a verification report by SKU from the box printer's first print run, and get photos of barcode stickers applied on the packing line. If there are several color or size options, keep each option's stickers separate and have the line pack only one option at a time so they do not get mixed. Also confirm that this was written into the work instructions at the pre-production meeting. For how to run that meeting, see Episode 123.

Pre-Shipment Inspection Stage

Have the inspector bring a handheld scanner, scan the barcode on each sample, and check that the SKU in the mapping table matches the actual contents. Check carton labels the same way, and confirm the quantity inside each carton matches the ITF-14 number. Have scan results recorded in the report by SKU, with photos. For pre-shipment inspection, see Episode 100.

6. Example Request Wording for the Factory

Put the wording below in your purchase order or packing instructions, and barcode size and placement are no longer left to the factory's discretion. It also makes it easier to assign responsibility if a receiving rejection happens.

"条码须按我方提供的矢量文件印刷，不得缩放、截短或改变比例。单品盒使用EAN-13，按100%尺寸印刷，黑色条、白色底，左右须留足空白区；外箱使用ITF-14，印刷在相邻两个面。外箱标签须使用热转印打印，禁止使用热敏纸。条码印刷质量须达到ISO/IEC 15416 C级（1.5）以上，首批印刷须每个SKU用条码检测仪检测3个以上并提供检测报告。包装时须逐个扫描核对条码与SKU对照表，不同颜色、尺寸的产品不得混装。条码号码、尺寸、位置未经我方书面确认不得更改。"
(Barcodes must be printed from the vector files we provide and must not be scaled, truncated or changed in proportion. Retail boxes use EAN-13 printed at 100% size, black bars on a white background, with full quiet zones on both sides. Master cartons use ITF-14 printed on two adjacent sides. Carton labels must be printed by thermal transfer; direct thermal paper is not allowed. Barcode print quality must be ISO/IEC 15416 grade C (1.5) or better, and on the first print run at least 3 pieces per SKU must be measured with a barcode verifier and a report provided. During packing, each barcode must be scanned and checked against the SKU mapping table, and products of different colors or sizes must not be packed together. Barcode numbers, size and position may not be changed without our written confirmation.)

7. Three Real Cases

These are anonymized versions of patterns we often see in consultations. Amounts and figures are examples.

Case 1 — Plastic Food Storage Container Sets

This is the case from the start of the article. The 1,200 rejected units were relabeled with new barcode stickers at a domestic warehouse and resubmitted, costing about 4 million won in labeling labor plus return and resubmission freight. From the next order, the brand had the factory print a white rectangle on the back of the kraft box first and then a 100% size barcode on top. The shrink film was changed to wrap around the barcode area, and packing could start only after the verification report for the first print run came in.

Case 2 — Amazon FBA Receiving Labels

A company shipping camping chairs to Amazon FBA in the US got a receiving delay notice. The factory had printed FNSKU labels on direct thermal paper, and the heat inside the container in summer faded them to gray. The company switched to thermal transfer labels and had sample labels scanned and photographed at pre-shipment inspection. Temperature and humidity inside containers are covered in Episode 118.

Case 3 — Activewear with Color Options

A company importing leggings in black and gray kept getting customer messages saying "I ordered gray and got black." It turned out the factory had packed both colors at the same time on the packing line, and some barcode stickers got swapped. Because the barcodes scanned fine, there was no problem at fulfillment center receiving; it only surfaced after delivery to customers. The company then split packing time slots by color and revised the work instructions to require a scan check right after packing. For returns handling, see Episode 55.

8. Common Mistakes

• Using random barcode numbers instead of numbers from GS1
• Sending design files as images so the factory redrew or resized the barcode
• Printing barcodes directly on kraft or colored box backgrounds
• Putting the unit barcode on the master carton as is
• Passing barcodes just because a smartphone app could read them
• Checking only that barcodes scan, without matching them to the actual SKU in the box

9. Barcode and Label Checklist

Spec and Design Stage

• Built a barcode mapping table by SKU using numbers from GS1
• Decided the barcode type for each packaging level (EAN-13, ITF-14, channel label)
• Wrote magnification, quiet zone, colors and placement into the spec sheet in numbers
• Sent barcodes as vector files and stated that size must not change

Sample and Production Stage

• Checked barcode size and numbers on the print proof
• Received the verifier report for the first print run
• Put sticker storage by option and packing order into the work instructions

Pre-Shipment Inspection Stage

• Scanned sample barcodes with a handheld scanner
• Checked that the scanned SKU matches the actual contents
• Confirmed carton labels match case pack quantities

Wrapping Up - Verifying "Printed" with Scan Results

Barcode problems rarely show up at the factory or at inspection, then hit all at once at fulfillment center receiving or customer delivery. A receiving rejection ends with relabeling costs, but a barcode that reads as another SKU leads to mis-shipments, returns and falling reviews. Writing standards into the spec sheet in numbers and collecting verification reports and scan-check records does not cost much.

There is something you can do right now. Pull out the barcode mapping table by SKU for the products you sell and match each number against the factory's latest box print files. If there is no mapping table, or even one number differs, build the mapping table and barcode requirements sheet and send them before your next order.

StartMade supports you on the ground with barcode mapping tables and packing instructions, box print proof checks, first print run verification, and scan-check inspection before shipment. If you have already had a receiving rejection, we start with finding the cause and relabeling. If you are preparing a new product, we start with the barcode requirements sheet.