Within Teamwork Projects you can view your monthly or annual invoices from the site settings.
Note: Only a site owner or site admin can access the site settings.
To view, click your profile image in the top right corner of your site, and select 'Subscription' from the dropdown:
In the Subscription area, you will see a list of any past invoices associated with the account below your plan summary:
Note: If you choose to pay via PayPal you will not receive an invoice to view in this area. Invoices for payments through PayPal can be viewed with them directly.
For more information see: Changing the email address for your subscription invoices