In Microsoft Entra Access Reviews, the "Upon completion settings" determine what happens after a review cycle ends - especially what happens when reviewers fail to take action. To automatically remove guest users who were not reviewed (or whose memberships were not approved), you must configure the "If reviewers don't respond" option under the Upon completion settings to "Remove access." The Reviewers and General sections define who conducts reviews and their frequency, while Advanced settings provide notifications and reminders.
From SC-300 content:
"You can specify actions upon completion, such as removing users not reviewed, keeping access unchanged, or approving all. The 'Upon completion settings' section controls this behavior."