How can I transfer a domain name from one SiteGround account to another?
To transfer a domain name from one SiteGround account to another, it must be associated with a website. If you haven’t created a website for your domain name yet, you can see here how to do that.
After that, you can transfer the ownership of the website, including the domain name, from your Client Area -> Websites -> All Site Options button next to the website entry -> kebab menu (three dots) -> Transfer Ownership.
Note that the process must be initiated from the client that currently has the domain name and website. During the process you will be required to provide the name and email address of the new owner.