The audit flags four kinds of issues. All of them are fixed in Shopify admin, in the variant's Barcode field — EasyLink picks the change up automatically.
Missing barcode
The variant has no barcode. If you own GTINs for this product, paste the right one in. If you don't own GTINs yet, see Getting GTINs below.
Malformed barcode
The value is GTIN-shaped (8, 12, 13, or 14 digits) but its check digit — the last digit, computed from the others — doesn't match. This is nearly always a typo: a swapped or mistyped digit. Compare against the number printed under the barcode on the physical product or your supplier's spec sheet, and re-enter it carefully.
Internal code
The barcode field contains something that isn't a GTIN — a custom warehouse code, a SKU, or a made-up number. Those are fine for internal workflows, but only a licensed GTIN can go into a GS1 Digital Link. Move internal codes to the SKU field (or a metafield) and put the real GTIN in the barcode field.
Duplicate barcode
Two or more variants share the same barcode. GS1 rules are strict here: every sellable variant (each size, colour, flavour) needs its own GTIN. Assign a distinct GTIN to each variant. Duplicates can't be published — EasyLink can't know which product a scan should resolve to.
Getting GTINs
EasyLink never sells, rents, or invents GTINs — numbers from anywhere other than GS1 can collide with other companies' products. If you need GTINs:
License a GS1 Company Prefix (or individual GTINs) from your local GS1 member organisation — start at gs1.org/standards/get-barcodes.
Assign one GTIN per variant, and record them in Shopify's barcode fields.
Re-run the audit — they'll show as Valid, ready to publish.