Hey @jh999 

Thank you so much for reaching out to the Klaviyo Community for help with updating your customer profiles via CSV file uploads!

Under the List & Segments tab you can click on the three dots on the right of the list you want to update and then click import data. This will allow you to upload the CSV with the updated information.

Just make sure the CSV file is formatted correctly so it updates each profile properly. The guide to import profile properties will walk you through every step and formatting to make sure you are successful. 

Hope this helps!

Thanks @stephen.trumble 

My question is really how to update rather than insert a new customer.

So, if John Smith is already in a  list in Klaviyo but he has changed his address how do I make the update via a .cvs file without adding him in twice.

Hope that makes sense. 

Hey @jh999 

As long as the CSV file if formatted properly it will not duplicate any existing profiles but rather just update their profile properties with their new data. The process to update vs create new is the same, as long as the first column in the CSV is “email” Klaviyo uses that to find existing profiles so they are updated without creating net new profiles.. Hope this helps clarify!

Thanks @stephen.trumble much appreciated. 

So if I moved email in the below .csv field list to the top then would that work? or does it need to be in a particular format?

customer_key
customer_name
customer_title
registered_date
opt_in_status
housenamenumber
streetname
address1
address2
address3
address4
postcode
countrycode
email 
phonenumber

Hey @jh999 

Here is an article that shows how to format the CSV file for manual upload. Here is an example of how your CSV file should be formatted. After the first three columns, the custom profile properties can be added. 

1. Make "Email" your first column
   1. If you don't have the email, use "Phone Number" 
2. Use "First Name" and "Last Name" as the next two columns
3. Add your columns for custom properties (e.g., "Gender")
4. Add the property value for each person
5.   

Thank you @stephen.trumble !