Within Teamwork Projects, you can delete a user so that they won't be able to log into your projects site. 

Any files the user has uploaded, time logged, comments or messages added or other content they've created will stay intact afterwards.

If they currently have any active tasks or milestones assigned to them, you'll be prompted to choose what to do with those during the process.

To delete, click the People tab at the top of your screen.

Select the People section for a list of users, contacts and collaborators on your site.

Choose the user you wish to delete from the list, and in the top right of the screen click the options button (three dots) and you can choose Delete User.

You will be able to choose what to do with the user's active tasks and milestones.

If you choose to reassign them, you will have options to pick a person and choose whether to reassign the tasks and/or milestones to them.

Note: Once this process of reassigning is complete you cannot undo it, so please check all details before proceeding.

In the Workload view, if you haven't reassigned the tasks then the time will be listed with the deleted user label.

Note: Once a user is deleted, they will remain in the Deleted People trash can for 30 days.

For more information, see: Adding people to a project