You have to use Resource Mover for this process. There are some CSPs that can make the move from PAYG to  MCA-E initial conversion to CSP without breaking down resources in a migration. It’s all done via clicks and transfer requests. Moves subs from PAYG to MCA to CSP and no resource mover is needed. I know of at least one VAR that’s been doing this for months now. They have to be Azure Expert – https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/mpa-request-ownership

Issues

Azure Stack Hub Resources: Resources in Azure Stack Hub cannot be moved between resource groups or subscriptions.

API Management Service (Consumption SKU): API Management services set to the Consumption SKU cannot be moved to a different subscription.

Azure Cache for Redis with Virtual Network: If an Azure Cache for Redis instance is configured with a virtual network, it cannot be moved to a different subscription due to networking limitations.

HDInsight Cluster Networking Resources: Networking resources associated with HDInsight clusters, such as network interface cards (NICs) or load balancers, cannot be moved across subscriptions.

Virtual Network with Resource Navigation Links: A virtual network cannot be moved to a different subscription if it contains a subnet with resource navigation links (e.g., an Azure Cache for Redis resource deployed into a subnet).

App Service Environments: App Service Environments cannot be moved to a new resource group or subscription. However, apps and plans hosted on an App Service Environment can be moved without moving the environment itself.

Apps with Private Endpoints or Virtual Network Integration: Apps with private endpoints or virtual network integration cannot be moved. These must be deleted and recreated after the move.

Free App Service Managed Certificates: Free App Service managed certificates cannot be moved. They must be deleted and recreated in the new subscription.

Virtual Machine Scale Sets with Standard SKU Load Balancer or Public IP: These cannot be moved across subscriptions.

Virtual Machines with Scheduled Patching: Virtual machines using scheduled patching cannot be moved across resource groups or subscriptions.

Resources with Plans in Different Subscriptions: Resources tied to a plan (e.g., Marketplace resources) cannot be moved if the plan is in a different subscription.

Network Watchers, Bing Keys, and Workspaces: These resources do not support movement between subscriptions by default.

Kubernetes Persistent Volumes (PV): Persistent Volumes in Azure Kubernetes Service (AKS) are not supported for migration between subscriptions.

Public IP addresses tied to specific resources, such as Virtual Machine Scale Sets with a Standard SKU Load Balancer or other dependent resources (e.g., VPN Gateways, Application Gateways, or NAT Gateways), cannot be moved across subscriptions. The dependency must be resolved or recreated in the target subscription.

Same with Backups , LoadBalancers and Application Gateways