How to Fix Missing or Incorrect Product Identifiers (GTIN, MPN, Brand)

Identifier issues are among the most common Merchant Center problems, and among the easiest to make worse. The wrong fix (inventing a GTIN, reusing an internal SKU, or setting identifier_exists to false on branded products) can turn a limited-visibility warning into a disapproval.

This guide focuses on fixing the issue. For a plain-language explanation of what GTINs, MPNs and brands are, see product identifiers explained.

What the identifier issue means

Google’s unique product identifier (UPI) rules ask for the identifiers a manufacturer assigned to a product: usually a GTIN, the brand and, where relevant, an MPN. These values are identical across every retailer selling the same product, which is how Google matches your listing to the right product.

Google recommends GTINs and recommends submitting all three identifiers where they exist. It also says products that have an assigned GTIN but are submitted without it may have limited visibility. Incorrect identifiers can lead to disapproval.

The GTIN fix article sums up the requirement: provide brand plus GTIN or MPN according to the UPI guidelines, and use identifier_exists where needed.

Typical issue patterns

• Missing GTIN: Google believes the product has a GTIN but your data doesn’t include it.
• Incorrect GTIN: the value is invalid, belongs to a different product, or was reused across products.
• Missing brand or MPN: no GTIN is present, and the fallback brand plus MPN is incomplete.
• identifier_exists used incorrectly: set to false for a product that does have identifiers, or left out for a product that has none.

Which identifiers your product needs

Find your product type in the table, then submit exactly what it calls for.

Product situation	What to submit
Branded product with a manufacturer barcode	gtin + brand (and mpn if you have it)
Branded product, no GTIN assigned, manufacturer part number exists	brand + mpn
Product has a GTIN but you can’t find it	Leave gtin blank; don’t substitute your own SKU
You make the product yourself (custom, handmade) with no official brand	Your store name as brand + an MPN you choose
One-of-a-kind or vintage item with no identifiers	identifier_exists = false; don’t include gtin, brand, mpn or SKUs
Books	ISBN as the GTIN (ISBN-13 recommended); brand not needed where there is no clearly associated brand
Movies and music	GTIN if assigned; brand not needed where there is no clearly associated brand

Products that commonly have no GTIN

Google lists examples of products that often don’t have a GTIN: store brands, replacement parts, OEM parts, custom-made goods, books published before 1970, vintage and antique items, and pre-order products. If your product is one of these, check whether a GTIN was actually assigned before deciding it has none.

Store brands and private label products

If you registered barcodes for your own brand, submit them as GTINs with your brand name. If your store-brand products have no GTIN, Google’s guidance for products you manufacture yourself applies: your brand name plus an MPN of your choice. Practitioner tip: keep that MPN stable and unique per product, because it becomes the identifier Google uses.

GTIN formats at a glance

Google accepts several GTIN types. Checking the digit count is a quick way to spot a wrong value.

Type	Format	Where it’s used
UPC (GTIN-12)	12 digits	North America
EAN (GTIN-13)	Typically 13 digits, sometimes 8 or 14	Outside North America
JAN	8 or 13 digits	Japan
ISBN	ISBN-13 recommended (starts with 978 or 979); ISBN-10 deprecated since 2007	Books
MPN	Alphanumeric	Manufacturer part number, used with brand

When to use identifier_exists

identifier_exists tells Google whether the product has manufacturer identifiers. Google says to set it to false for one-of-a-kind or vintage products. When no identifiers were assigned, don’t include gtin, brand or mpn, and don’t fill them with SKUs.

Setting it to false on mass-produced, branded products is a common mistake. It removes the warning in the short term, but if the product has a GTIN, the listing loses the matching that identifiers provide and may still be flagged. Use it only where it’s true.

Custom products you make yourself are a middle case. Google’s guidance is to use your store name as the brand and an MPN of your choice, which means the product does have identifiers you assigned.

How to confirm the cause

1. Open Products > Needs attention, select the identifier issue and read the Issue Details Page, including the sample products.
2. For a sample product, check what Merchant Center received: the gtin, brand, mpn and identifier_exists values.
3. Compare those values with the product’s packaging, the manufacturer’s spec sheet or your supplier’s data.
4. Check whether the same GTIN appears on more than one of your products (a sign it was copied).
5. Check your platform or feed tool to see which field it sends as gtin and brand. A mapping problem usually affects every product at once.

If every product is affected, the cause is almost always a mapping or export issue. If only some are affected, the cause is usually missing data in those product records.

How to fix identifier issues

For a few products

Open the product from Needs attention and use Edit product. This is fine for products added directly in Merchant Center. If the product comes from a platform or feed, also fix it at the source, or the next sync may overwrite your edit.

For many products

1. Download the list of affected products from Needs attention.
2. Collect correct identifiers from suppliers or manufacturers. Don’t guess.
3. Update the values in your platform, feed tool or spreadsheet.
4. Resync, re-upload or reprocess the data source.
5. Check Needs attention again. Google notes the fix takes time to reflect.

When you can’t change the source

A supplemental data source can add gtin, brand or mpn values matched by product ID, and attribute rules can set or transform values in bulk (for example, setting brand from another field). Both are described in the guides on supplemental feeds and feed rules.

Where to edit identifiers in Shopify and WooCommerce

Exact field names vary by version and app, so treat this as a map of where to look rather than a click path.

Shopify

• GTINs are usually stored per variant, in the variant’s barcode field. Each size or color needs its own value if the manufacturer assigned one.
• Brand is commonly taken from the product’s vendor field. Check that it holds the real brand, not your supplier’s company name.
• If you use the Google & YouTube app, edit products in Shopify and let them sync, rather than editing in Merchant Center.
• See Shopify Merchant Center troubleshooting for sync issues.

WooCommerce

• Depending on your WooCommerce version and feed extension, GTIN may be in the product’s inventory settings or in a field added by the extension.
• Variable products need identifiers on each variation, not just the parent.
• Check which field your Google for WooCommerce setup or feed plugin reads for gtin, brand and mpn.
• See WooCommerce product feed errors for mapping problems.

Preventing identifier issues

• Make GTIN, brand and MPN required fields when adding new products.
• Ask suppliers for identifier data with every new product list.
• Never duplicate a product record to create a new product without clearing its identifiers.
• Keep a short list of product types where you use identifier_exists = false, and why.
• Review identifier issues in Needs attention after importing new products or changing feed tools.

When to get help

Identifier fixes are mostly data work. It’s worth getting help when thousands of products are affected, when the cause is a mapping issue you can’t trace, or when identifier problems sit alongside other issues. Our disapproval service and product feed optimization cover both.

Frequently asked questions

Sources

• Google Merchant Center Help — How to fix: Missing or incorrect GTIN
• Google Merchant Center Help — About unique product identifiers
• Google Merchant Center Help — Product data specification
• Google Merchant Center Help — The Needs attention tab
• Google Merchant Center Help — Set up your attribute rules
• Google Merchant Center Help — Create a product data source
• WooCommerce Docs — Google for WooCommerce: Get started

Last reviewed October 10, 2026 against the official documentation listed above. Google changes Merchant Center features and policies regularly — always confirm details in your own account.