Once the tenant subscribes an offer with Billing Service, the Billing Resource Provider should be registered in that subscription to make use of the features in tenant portal.
NOTE: Irrespective of registration at tenant portal, the billing solution will capture usage for all Azure Stack subscriptions and will start computing prices for the subscription that has billing service as part of the plan/offer. The registration in the tenant portal is only required if the tenant wants to view their cost from within the tenant portal.
Click ‘Subscriptions’ extension in Azure Stack Tenant Portal
Choose the Billing Service enabled subscription
Choose 'Resource Providers' section
Click ‘Register’ for the ‘CloudAssert.Billing’ Provider