It's only related in that the Year End function (like the Period End function) can actually do the moving/clearing by allowing the user to choose to clear the fully paid transactions to history and if so a date on which to base the clearing process.

BTW - at the risk of stating the obvious, "fully paid" really means any and all transaction types whose current (or outstanding) amount is zero. It does not just relate to invoices that have been fully paid by cash payments.