deallocated vm keep config and IP

Sorry if this has been covered before....

We would like to Stop (Deallocate) a lot of Azure VM's overnight - for billing purposes.
We have Test, Development & Pre-Production environments which are growing rapidly. 

We will always leave the PRODUCTION core AD DCs running 24/7/365

The reak question is -- Is there a way to ensure that the servers we deallocate, when started back up, keep their same IP address and config??  

---[EDIT - have learned that static IP's will be kept even if VM is deallocated]---

So, how to ensure the VM keeps the resources previously allocated.

Or is it simply not possible to do that if you deallocate a VM.

Thanks

Nathan