You have the option of blocking a guest. This means that the guest cannot be added to any bookings as long as they are blocked.
1. Open the Guest Management.
2. Select the guest you want to block in the guest list.
3. In the context menu (right-click) or the Actions menu select the item Block This Guest.
When the reason for blocking the guest has been resolved, you can use the context menu or the Actions menu to Unblock the Guest. This will allow the guest to be added to bookings again.