SSCC-18, without the standards document
Eighteen digits, one check digit, and a serial number that must never repeat. Most label failures are not printing problems; they are numbering problems.
Get a fixed quote Decode an 824
What the eighteen digits are
An SSCC-18 is four things joined together:
- Extension digit (1 digit) — yours to assign; usually 0 or 3 for pallets.
- GS1 company prefix — issued by GS1, 7 to 10 digits depending on your licence.
- Serial reference — fills the remaining digits, unique per pallet or carton.
- Check digit — computed from the other seventeen, never chosen.
The check digit, in one paragraph
Number the seventeen digits from the right. Multiply alternating digits by 3 and by 1, sum the products, subtract the sum from the next multiple of ten. That result is the check digit. Every barcode library does this for you; the failures come from systems that build the number as a string and append a zero.
If you just want the digit, the SSCC-18 calculator computes it from seventeen digits.
Where it goes, and how it is encoded
The number is encoded as a GS1-128 barcode under application identifier (00). On a pallet label it appears on at least two adjacent sides; on a carton label, once per carton. The human-readable digits sit under the bars so a person can key it when the scanner fails.
- Pallet label: 4x6 in is the common stock, but the guide governs size and placement.
- Every carton needs its own number when the retailer requires carton labelling.
- The 856 must carry the same numbers, in the same order, as the physical shipment.
The four failures
These account for nearly every label chargeback I have seen described:
- Reused serials — a printer reprints last week's label, and the DC sees a duplicate it has already received.
- Wrong check digit — generated as text, not computed, so the barcode scans but the number is invalid.
- Label not scannable — printed too small, on the wrong stock, or at an angle that a handheld rejects.
- ASN disagreeing with the pallet — the numbers are valid but belong to a different shipment.
A print test that actually proves something
Print one label on the production printer, scan it with the production scanner, and compare the decoded string to the 856 byte for byte. A PDF preview proves nothing: the failure is almost always in the printer's resolution, the stock, or the scan.
Questions
Do I need a GS1 licence to make SSCC-18s?
You need a company prefix, which comes from GS1 or from a retailer-assigned range in some vendor programmes. Do not invent a prefix; the number will collide with someone else's.
Can one SSCC cover a mixed pallet?
Yes. The SSCC identifies the pallet, and the 856 line items describe what is on it. What it cannot do is cover two pallets.
Does every retailer require carton labels?
No. Walmart and several grocery DCs do for many categories; others only require the pallet. The implementation guide for your vendor number is the authority.