The report tab will on its own depending on what fees you assign.
As soon as you assign fees it will show up as 'outstanding' on the report page. As soon as they are paid it will show up as income from Paypal or income from cash.
You can click any of the annual fees headings or the pay as you play headings for a full breakdown on who owns what, making it easier to track down those discrepancies.
You can even click into players for their own individual breakdown on where they haven't paid.