Google documented GG_ transaction IDs as a sign your own transaction ID is not being sent

Google added an 'Understand Google-generated transaction IDs (the GG_ prefix)' section to its help page on using a transaction ID to minimize duplicate conversions. Transaction IDs starting with GG_ are temporary, system-generated identifiers that mean the advertiser's own ID is not being assigned, which breaks deduplication, so a GG_ prefix should be treated as a blank transaction ID.

Google also updated the verification steps: inspect the transaction_id parameter in the Hits tab of Google Tag Assistant, or check the oid parameter on Google Ads conversion requests in Chrome DevTools. Advertisers seeing GG_ values in Tag Assistant or reports should check their data layer.