By default, the UseTabKey is True. If the UseTabKey property is True, the control inserts a TAB character at the caret position, or indents the selection ( if multiple lines are selected ) if the IndentOnTab property is True.  If the UseTabKey property is False, the control doesn't handle the TAB key. If the UseTabKey property is False, the TAB key focuses the next visible control in the form. If the Locked property is True, the UseTabKey property is False.