We have revamped the Billing area to make it easy to see your test allocation usage, manage Plans, tax information and receipts.
In Billing → Overview you can now see per Site test usage as well as delete your organisation.

Billing Overview shows test allocation usage for each Site
You can add or update your default credit card under Billing → Payment method. In Billing → Receipt History and Settings you can ensure your receipts include all necessary information for your tax department and accountants.

Receipt History and Settings allows for customising your receipts accordingly to your tax needs.
At any point, you can adjust your Plan accordingly to your usage.