There are two types of payment notifications: billing and documents for accountants.
Billing email will receive all information about subscription: quota alerts, bills, information about service block. You can set only one address as a billing address. It can be changed at any time.
Accountants will receive bills and acts only. You can set several emails for your accountants. Since in most cases accountants don't need to visit Dashly admin panel, so adding their email to the system will not create an account for them.
In order to add or to change emails for payment notifications move to Subscription section and change your billing email.