This article describes how to close an active iteration.
To close an iteration, first select the iteration row in the view. Its Properties, the Name and Status, will appear to the right.
Change the Status to Closed.
Once the view is refreshed, the iteration and its issues will no longer be displayed in the views by default. You can however, use the Show closed iterations option to toggle and bring them into the view, as needed.
It is possible to re-activate a closed iteration.