To change the PO number on file for your lab so that it will be used for future invoices (e.g renewal of your subscription or if you upgrade your plan), the lab admin (or in the case of enterprise subscription holders the organisation admin) must follow the below steps:
For a single lab subscription:
Select the lab settings button, located on the right hand side of the lab dashboard page.
For Enterprise subscription:
The settings for the subscription are located at the bottom of the left hand menu for the organisation admin.
In the lab settings, select the Subscription tab and click View Billing Details
This will open in a new tab the Clustermarket billing portal. Click on the lab subscription at the top of the menu and input a PO number into the box.