Hi Lauren,
I was on holiday last week so the answer is a bit late.
The system at the moment is setup that you accept also the non payers and they will appear in the Unpaid tab,
In the submit and accepted email we normaly have a sentence that the payment has to be done before <date> otherwise the entry will be removed from the startlist.
Now you can sent the payment reminder and if not paid you do unaccept so they will not be imported or if already imported will be set to 'Withdrawn'
Kind regards,
Thom Kerssies