Hello @Michael,
Thanks for sharing this question with the Klaviyo Community.
I did some digging and found the required format for .csv imports for Shopify. After reviewing, it appears if you re-format the column header from the Klaviyo exported .csv file to “Tags” (as they outline in their documentation for required formatting of the .csv) my assumption is that Shopify would “recognize” Tags and use that to update the original customer record -- associating it with the user’s email address.
I believe the current reason it is creating a net-new record is because the default Klaviyo .csv file is using another column header that isn’t “Tags”, and as a result, upon import, this net-new tag is created for the new customer record instead of updating the original customer record.
If this still doesn’t resolve the issue, I encourage you to contact Shopify support for more information since this question pertains to Shopify .csv import functionality. If they do have a different solution, it would be great if you could provide us with an update here on the thread so we can share this knowledge as I’m sure others will have similar questions as well!
Thanks for being a member of our Community.