When you subscribe to a Teamwork Projects plan, the default email address for the invoice and subscription emails will be your site owner address.
To change this to any other email address - for example, if your accounts team have a general address where they like to manage receipts - just go to the site settings menu in the top right of your screen and choose the 'Subscription' area:
On the subscription screen, click the "View Invoices" button on the right of screen to view your invoices.
Scroll to the bottom of the list of payments and here you'll find the link to update the address.
Note - only site administrators in the owner company can access this area.