Why a barcode that scans fine at the factory is rejected at the distribution centre

Why does a barcode that scanned fine get rejected?

“It scanned fine here” usually means one scanner, at one angle, read the code once. GS1 UK puts the difference plainly: a scanner simply beeps or not, whereas a verifier checks the barcode’s quality (GS1 UK). A code printed near the limit decodes on a forgiving scanner and fails on a different one, at a steeper angle, at conveyor speed or after the label has been scuffed in transit.

The other half of refusals has nothing to do with print. The DC reads the code without trouble and the number is wrong: an SSCC that was not in the advance notice, a label from another pallet, or the same SSCC used twice. A barcode verifier would grade that label as perfect.

What do GS1 rules require on cases and pallets?

On a GS1 logistic label the SSCC is the single mandatory element, carried in a GS1-128 barcode (GS1 General Specifications). GS1 also sets the minimum print quality: barcodes in general distribution, including ITF-14 and GS1-128 on cases and pallets, need at least 1.5/10/660, where 1.5 corresponds to ISO grade C (GS1 General Specifications).

GS1 South Africa tests barcodes with ISO 15416 verification methods and states that many retailers require its barcode test report when a product is listed (GS1 South Africa). That report tests samples before listing. It does not check what the labeller prints every day, which can drift with the print head, ribbon, label stock and speed.

How the grades are measured is explained in barcode verification and grading and the GS1-128 barcode guide.

What does the distribution centre actually check?

The SSCC, which identifies one logistic unit (GS1, SSCC), is the link between the physical pallet and the data about it: GS1 describes it as connecting the logistic unit with the information exchanged between trading partners by EDI (GS1 General Specifications). The GS1 Logistic Label Guideline describes the supplier using the same SSCC to identify stock when it is loaded for dispatch (GS1 Logistic Label Guideline). So the DC does not only scan the label; it looks the number up.

GS1 rules make two of these failures easy to cause. An SSCC must stay the same for the life of the pallet and must not be reallocated within one year of shipment (GS1 General Specifications, 4.3.1), so a label printer that restarts its counter, or a relabel with a fresh number that was never sent, both produce a pallet the DC cannot match. How the SSCC and its Application Identifiers are built is covered in the GS1-128 and SSCC guide.

What should be checked before a pallet leaves?

The checklist below turns the GS1 rules into checks a dispatch line can make. GS1 places all barcodes on a pallet between 400 and 800 mm above the base, at least 50 mm from a vertical edge, and recommends two identical labels on adjacent sides (GS1 General Specifications). The Logistic Label Guideline repeats the two-side recommendation (GS1 Logistic Label Guideline).

The first four rows are content checks a reader does on every pallet. The fifth is a print grade that only a verifier gives. The last decides where the reader is mounted: a fixed reader aimed at the 400 to 800 mm band reads every pallet the same way.

What about chargebacks and rejected shipments?

Suppliers often ask about chargebacks when a GS1-128 label fails and a shipment is rejected. Whether a retailer charges, refuses the delivery or relabels it at the supplier’s cost is set in each supplier agreement. We have not found published South African figures, so this article does not quote any. What is certain is that every refused pallet costs a return trip, relabelling and a late delivery, whatever the agreement says.

How do you stop it at dispatch?

Two checks, because they prove different things:

• Read every label before it leaves. A fixed code reader on the case conveyor or after the stretch wrapper reads each label, treats a no-read as a fail, and checks the SSCC against the WMS or dispatch record. Both required sides of a pallet can be read and compared. This catches unreadable, wrong, duplicated and missing labels on every unit. See pallet identification system and carton and pallet label verification.
• Grade samples with a verifier. At start-up, after a ribbon or label stock change, and at set intervals, labels are graded with a calibrated verifier, or sent to GS1 South Africa’s verification service. This proves the print stays above the GS1 minimum, which a reader cannot prove.

Many readers report a quality indicator for each read. A falling trend is a useful early warning that the print head or ribbon needs attention, but it is not a formal grade.

How do you find the cause after a rejection?

1. Get the DC’s reason and a photo of the label as it arrived. “No-read”, “unknown SSCC” and “label missing” point to different fixes.
2. Classify it: print (no-read, intermittent read), data (wrong or unknown number, fields run together) or presence (missing side label, two different labels).
3. For print: grade retained labels from the same run with a verifier. GS1 lists the usual causes, such as light bars, uneven inking or bar gain, with their remedies, so the report points to the printer setting to change (GS1 General Specifications, 5.12.5.11).
4. For data: compare the SSCC and fields on the photo with the WMS record and the despatch advice sent.
5. Close the gap with the matching dispatch check, so the next one is stopped at the dock rather than at the DC.

What should be recorded?

For each pallet or case: the SSCC read, the time, which sides were read, the result and, for failures, an image. When a DC queries a delivery, that record shows what left the dock. Readers and how they connect to the PLC and WMS are covered in choosing a fixed mount barcode scanner.

Separate the checks before the pallet leaves

Keep the failed layer in the exception record. Correcting print quality cannot resolve a wrong product identity, and a correct pallet association cannot repair an unreadable case label. This sequence helps the production and warehouse teams send the problem to the right owner.