How does waitlisting work?
Waitlist works by allowing attendees to register for an event, once a specific item has sold out. Once the item has sold out (if that item is set to allow waitlisting) a waitlist is started and the attendee can register for the sold out item but they are notified they will be placed on the waitlist.
With payment as 'Require and Charge' there is no payment accepted for waitlisted attendees, as they are not confirmed for the event. Once a spot opens up, you can allow any waitlisted attendees into the event and accept payment. Here are instructions on how to admit a waitlisted attendee and collect payment.