Hi @Robin Hitch ,
is the new subnet in the same vNet with the source subnet?
Than it's easy to get there:
Navigate to the NIC of the VM in the Azure Portal.
Click on IP configurations
- Verify the private IP Address is assigned dynamic (if it's a static IP Address change to dynamic first)
- Select the new subnet
- Click
Apply
If you want to switch the VM to a subnet in a different vNet you have to delete the VM but keep all Disks!. Create a new VM using the existing Disk(s) and select the new vNet and new subnet in the wizard.
Details you will find here: Create a VM from a specialized disk
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards Andreas Baumgarten