A missing identifier is a data-provenance question, not an invitation to invent a number. Before a feed supplier fills the GTIN column, establish which identifier the manufacturer actually assigned to that exact product and pack. A syntactically plausible number is still not evidence of assignment.
Who should use this acceptance brief
Retailers preparing product feeds and product-page specifications. Use this as a scoped commissioning task for a website supplier. Where system evidence is required, a teaching file is not a substitute.
Source-bound platform fact
Merchant Center guidance distinguishes assigned GTINs from internal identifiers. Products without an assigned GTIN need the applicable identifier rules, not fabricated GTIN values. Google Merchant Center: GTIN · Checked 16 October 2026.
Filled teaching example
Synthetic example, not a client case. Inputs, expected decisions and counterexamples follow; no live platform integration is claimed.
On narrow screens, scroll to read the complete table.
| Input / case | Check basis | Expected decision |
|---|---|---|
| supplier SKU = CHAIR-BLK | no assigned-number evidence | hold GTIN field |
| pack-6 has documented GTIN | exact pack match | candidate for validation |
| single-item GTIN on pack-6 | pack mismatch | hold |
Run the acceptance exercise
- Request the manufacturer record, exact pack identity and the person who approved it.
- Compare product, variant and pack, then validate the identifier format separately.
- Keep missing evidence visible in the feed worklist rather than filling a plausible placeholder.
Interpret the result and retain evidence
The fixture approves only an explicitly assigned, exact-pack record as ready for further format checking. It deliberately does not generate a live GTIN or claim registration. Ask the feed supplier to distinguish “provided”, “format checked” and “assigned-product match” in the handover; those are three different evidence states.
Limits before implementation
Exclude registry lookup, product authenticity and Merchant Center approval. An unknown assignment is unknown, not proof that a product is exempt.
Replay the finite example
Save both files in one folder and run with Node22.13 or newer. These finite checks are not a live service or certification. Filled inputs and expected outputs · Inspectable functions
node decision-check.mjs product-gtin-provenance.json