Merchant Center reports “Incorrect product identifier [mpn]” when the mpn attribute holds something that is not the manufacturer’s part number, most often the shop’s own SKU or a placeholder. Enter the number the manufacturer uses for the product, or leave the field empty; an MPN is only needed, together with brand, for products that have no GTIN.
| Shown in Merchant Center as | Incorrect product identifier [mpn] |
|---|---|
| Attribute | mpn |
| Effect | Warning |
| Where to find it | Products → Needs attention, then filter by this issue |
| Free check | Reported by the free feed check |
What Merchant Center means by “Incorrect product identifier [mpn]”
The mpn specification is for the Manufacturer Part Number: the code the maker assigns to the product, the same in every shop that sells it. When the field holds something else, Google’s product issues list gives the issue as incorrect_mpn_error, “Incorrect product identifier [mpn]”, with the fix “use the Manufacturer’s Part Number (MPN)”. Google’s identifier overview sets out when an MPN is needed: with the brand, for products that have no GTIN.
The value is rejected as an identifier, so the product goes back to being one without identifiers, with the warnings that brings. A wrong MPN does not help matching; it only looks, to Google, like a catalogue that fills required fields with whatever is at hand.
Why it happens
- The shop’s SKU mapped to
mpn, the single most common cause; many export templates do it by default. - The GTIN repeated in the MPN field to fill it.
- Placeholders:
N/A,none,0. - A model name in words rather than the manufacturer’s code.
How to fix it
In Shopify
In Shopify’s Google & YouTube channel, you add the brand and MPN for products without barcodes. If your feed app takes the MPN from the SKU, turn that mapping off. FeedRobin does not send the variant’s SKU as mpn; a manufacturer’s part number can be added in an mpn column of the sheet on the Corrections page.
In WooCommerce
Our free plugin never sends the SKU as an MPN, on exactly this ground: your SKU identifies the product in your shop, not at its manufacturer. It sends the GTIN from the 9.2 field, or from Google for WooCommerce, when there is a valid one, and no identifier_exists. If your feed comes from another tool, check its MPN mapping and remove SKU from it.
In a CSV or XML feed
Empty the mpn column for every row where the value is not a manufacturer’s part number. Fill it only where you have the real code and no GTIN, together with brand. Rows with neither GTIN nor MPN that are genuinely unbranded or handmade get identifier_exists = false.
How long until Merchant Center clears it
After the next fetch with the corrected or emptied value, check that the issue is no longer listed on the Needs attention page. Google’s page on unique product identifiers says: “Products that have a brand [brand]and MPN [mpn], but are submitted without these attributes, may have limited visibility.”
What FeedRobin does about it
For a feed URL, the free feed check counts products with nothing to identify them by: no GTIN and not both brand and MPN. It does not check whether an MPN is genuine. In the Google, Meta, Microsoft and custom feeds we serve, mpn is sent only for a product that has no GTIN and has a brand. From a Shopify store, the variant’s SKU is not sent as mpn; an mpn comes only from the sheet on the Corrections page or a feed rule. From a feed URL, a sku value is read as mpn: in XML when the item has no mpn value, in CSV when the sku column comes before the mpn column or there is no mpn column.
Questions merchants ask
What is the difference between a SKU and an MPN?
A SKU is your code for the product in your shop, chosen by you. An MPN is the manufacturer’s code for it, printed in their catalogue and on the box, the same in every shop that sells it. Only the second identifies the product outside your store.
Do I need an MPN if I have a GTIN?
No. A GTIN is sufficient. Brand plus MPN is the alternative for products that have no GTIN, per Google’s identifier rules.
My products are own-brand and have no part numbers. What goes in mpn?
Nothing. If they also have no GTIN, set identifier_exists to false and leave gtin and mpn empty. Inventing an MPN from your SKU is exactly what this issue reports.
Sources
- MPN [mpn] — Google Merchant Center Help
- About unique product identifiers — Google Merchant Center Help
- Product issues (Content API for Shopping, sunset on 18 August 2026): common item-level issue codes with their description and detail
- Shopify Help Center: Syncing your products