Within Teamwork, you can mark any of your projects as complete in the project's settings.
Click the three dots to the right of the project name to open the project options menu. In the Manage Project tab, click More Options and select Complete from the pop-out menu.
You can also complete a project via the Dates section of the project details pane on the left of the Overview section of the project. Click one of the existing dates or select the Edit option.
In the project dates modal, you will see an option at the bottom to mark the project as complete. Click Set Project Dates to save the changes.
The project details sidebar in the Overview tab will be updated with a note of completion.
Note: Completing tasks and milestones will not automatically complete a project so you need to mark the project itself as complete.
For more information, see: Completed Projects