First, create an individual Betterment account. Remember, you do not have to fund your individual account, and you can delete it afterwards without any fees or penalties. After you’ve created your individual account, follow the steps below to create a joint account.
Log in to Betterment, either on a web browser or your mobile app.
Click “Add New” from the menu if on a web browser, or “Add goal/account” if on the mobile app.
Follow the on-screen prompts.
An email invitation will be sent to the joint account holder, so give them a head’s up.