The reader itself isn't attached to any specific account.  You could share a reader with a friend, for example.  The account that the phone/tablet is signed into controls what account the reader is connected to at that moment. You can only link one back account to a Square account.  If you have multiple locations, you can have different bank accounts for each location.  You could also create two different accounts so you can have different bank accounts.  You'll find more information on that here.  https://squareup.com/help/us/en/article/5225-create-multiple-square-register-accounts