SSCC-18 Explained: The 18 Digits, the Check Digit, and Why You Can Never Reuse One

The Serial Shipping Container Code is an 18-digit number that uniquely identifies a logistic unit — a pallet, a carton, a returnable crate. It is not a product code: two identical cartons in the same shipment get different SSCCs. That uniqueness is what lets a warehouse say «this specific box arrived» rather than «a box of this product arrived».

The 18 digits are built from an extension digit, a GS1 company prefix, a serial reference and a check digit. The extension digit (0–9) lets a company multiply its serial capacity without asking GS1 for another prefix. The serial reference is assigned by the company and must never repeat for the same prefix. The final digit is a mod-10 check computed over the first 17 digits with alternating weights of 3 and 1 from the right.

In a GS1-128 symbol the SSCC is encoded under application identifier (00), which is fixed-length, so no FNC1 separator is needed after it. The human-readable text below the barcode should show all 18 digits, usually grouped for legibility. Retail and parcel systems compare the scanned value with the EDI despatch advice (DESADV); if they disagree, the pallet is treated as unknown even if the barcode scanned perfectly.

Never reuse an SSCC, even after the goods are sold or scrapped. Reuse breaks traceability and can merge two shipments in a customer’s system. Generate SSCCs from a controlled sequence, reserve blocks for each site, and store the mapping between SSCC and order. A generator that computes the check digit for you removes the most common data-entry error, but the sequence itself still needs governance.