Reusing subscriptions

Hello,
Is it possible to reuse a subscription? My company currently has a contract with 20 desktop subscriptions available. During testing some installations are no longer needed and are removed from the subscription manager. Currently I have 3 physical systems and 1 virtual system in use however my portal states that I have 7. All of the installs that were removed were done through the manager portal itself, not within the RHEL OS.
Are those 3 subscriptions able to be recovered for additional use?
Thanks.