Fix “Missing value [gtin]” on Google Merchant Center

The "Missing value [gtin]" issue is the most common blocking issue on Google Merchant Center and one of the most operationally annoying because the fix path varies so much by case. For some products the GTIN simply needs sourcing — the manufacturer assigned one, you just don't have it. For other products the GTIN is in your system but mapped to the wrong feed field (Shopify's `barcode` field is the classic offender — many feed pipelines miss it). For a third category, the product is genuinely GTIN-exempt and you need to declare `identifier_exists: false` explicitly.

The triage instinct that works: filter the affected SKU list, then categorise. Branded products from manufacturers — source the GTIN, almost always findable. Own-brand products from your own manufacturing — your store name as brand, set identifier_exists: false. Resold items where you don't know if a GTIN exists — search the manufacturer's website; almost always present for standard retail goods.

The trap most catalogs hit: bulk-setting identifier_exists: false to bypass the issue. Channels audit this. Accounts using identifier_exists heavily on branded products eventually face account-level quality reviews, and the consequence is wider than the initial issue you were trying to dodge. Source the GTINs where they exist; declare exemption only where it genuinely applies.

For high-volume catalogs where GTIN sourcing across thousands of items is impractical, the AI Shopping Feeds Optimiser can extract GTINs from product images, supplier data, and existing descriptions where the GTIN exists somewhere in your data but isn't mapped to the right field. The Audit feature finds every instance of missing GTIN across Google, Meta, TikTok, and Pinterest in one pass.