Collecting fees after someone signs up

Some of our more ambitious scouts have registered for events before we send out invites since the events are on the Troop Track calendar as place holders. Once we send out invites the registration fee is added in. Does TT go back and request payment?

No, it does not go back and request payment. As an admin you could go into the Payment screen and it may give the option to charge the fees from there, I forget exactly what options there are for this particular situation. You may have to remove their RSVP and add them back to charge he fees.