In September we said Google Merchant Center would enforce that all products would have unique product identifiers (UPI) within the product feed. If there was not UPI, Google would immediately disapproved and no longer showed in free listings. That is now changing to limited performance enforcements.
Google said the new limited performance enforcements will result in "products that are missing such attributes will remain eligible to serve but their performance may be limited."
As a reminder, unique product identifiers include identifiers such as GTIN [gtin], MPN [mpn], and brand [brand]. Now all products require a combination of unique product identifiers. If these required attributes (GTIN [gtin], MPN [mpn], and/or brand [brand]) are not provided, your products will remain eligible to serve but their performance may be limited.
These new limited performance enforcements go into effect in November 2021.
Forum discussion at Twitter.