When an ads account is created, the original account creator is designated as the "Accounting Admin" by default. However, any Admin on your account can be designated the "Accounting Admin" for purposes of receiving payment information, receipts, invoices, balance notifications, and other accounting-related information.
To add an Accounting Admin, click the "Team Management" option on the left-hand side of your dashboard, then click the menu next to any user on your account. Choose "Set Accounting Admin" from the drop-down menu.
This user will now receive all information relating to your billing and accounting.