How to Make Someone Owner in Your Subscription in Azure

Make Someone Owner in Your Subscription

1. Visit Subscriptions in Azure portal.
2. Select the subscription that you want to give access.
3. Select Access control (IAM) in the menu.In the Role box, select Owner.
4. In the Assign access to box, select Azure AD user, group, or application.
5. In the Select box, type the email address of the user you want to add as Owner. Select the user, and then select Save.

This gives the user full access to all resources including the right to delegate access to others. To give access at a different scope, like a resource group, visit the IAM menu for that scope.

Reference Link

https://docs.microsoft.com/en-us/azure/billing/billing-add-change-azure-subscription-administrator