For Professional subscription plans, account architects can find and download invoices via your Billing page. 

For Enterprise plans, please contact our friendly accounts team to receive copies of any historical invoices. 

Your billing page can be accessed by clicking on "Account settings" in the profile menu dropdown and then "Billing". 

In the "Invoices" table at the bottom of this page, you can click "Download" against the relevant invoice to download an invoice pdf to your local machine.