A Billing Account is a method of tracking spend within a specific public cloud. It is linked to a single fund with one or more users. Use more than one Billing Account per cloud only when you need to track spend separately. You may create a new Billing Account on a different public cloud at anytime. Note that users cannot see/manage services between different Billing Accounts without special roles being added so only create Billing Accounts when no sharing is needed or if you are an advanced user.