In Flow, only Organization Admins have access to billing information, including invoices.
All existing invoices can be downloaded by going to your Billing and Organization settings.
Once you’re on the Organization Settings page, click ‘Manage Subscription’. Next, click on‘View Billing History’. This will pop up a scrollable window from which you can select the invoices you’d like to download.
Your invoices will download as a PDF to wherever your downloads are set to land on your device.