We had a contractor working with us who has now become an employee. I’ve added his new employee email address to our organization but I can’t get his contractor email account to stop showing up in the Assignee list as a guest when adding new task. He isn’t part of the Team of the organization or of the projects he’s on.
How do I get that old guest account to stop displaying from the Assignee drop-down?
Hi @anon67220114
Welcome to the community 
If you are the admin of the organisation workspace you are in, you can go to the Admin Console and remove your colleague’s account with the old email address. Once you do so, Asana will automatically create a project that houses any open tasks for them which you can then assign to them with the new email address in one go. Once you remove them from the admin concole, they will no longer appear as an option for you when assigning new tasks.
There is also guidance on how to merge 2 accounts. Below is the link - scroll down to multiple accounts and merging section for details:
I hope this helps!
Rashad
If you are using the basic version of Asana:
Hope this helps!
Neither of these responses works. When I go to Members within the Team Settings he doesn’t show up as a Member there and when I go to Members or Teams within the admin console it says I have to upgrade to Premium to view those.
You have to go to the team settings of a team he was a member of.
If you aren’t able to locate them in a team I suggest:
Hi @anon67220114! Adding to what @Christine_Bolton mentioned, please note that it is 3 clicks: Remove > Remove Access > Deprovision
The second click removes the person from the team, and the third click fully removes them from your Organization 
Hope this helps!
That did the trick - thank you ladies!!