For initiatives with defined time slots, you can choose to close registrations before the initiative starts. To set or change this deadline:
From the Administration menu, go to My Catalog
Click on ✒️ Edit next to the initiative
Under Planning, click on Registration close and select the desired time frame from the drop-down menu: 24h, 48h, 72h, 7 days, 14 days, 1 month, no limit