Sometimes, it may be necessary for management or billing processes, to move an Azure Web App or other Azure Resources between Azure Subscriptions. It is simple process that can be done in Azure Portal.
In this example, we will move the ‘alvarnetwww’ App Service Plan and App Service to a different Subscription and Resource Group ‘AlvarnetWWW’ (in same GeoLocation) .
1. In the Essentials blade of the source Resource Group ‘alvarnetwww’, click on the Subscription name > change.
2. The Move resources blade opens > Resources to move > Select all
Move these resources to: Select the Subscription via the dropdown option
Resource Group > Select existing resource group or New resource group
New resource group was selected and the Resource Group AlvarnetWWW created here
OK > Azure begins moving the resources
3. The Azure notification appears with a full description of what was moved from where to where.
4. Opening the new Resource Group on the destination Subscription shows the App Service Plan and App Service that have been moved.
5. Verify that website still resolves although the resources have changed subscriptions.
6. It is a best practice, if the initial Resource Group on the source Subscription will not be used again and is empty, to delete it from the source Subscription.
Reference: Move resources to new resource group or subscription