This is for whoever keeps the books. If your area does not, you will not see these screens.
On the Subscriptions screen you get Issued, Collected and Still to collect. The last one is the real number: it discounts what is already paid, part payments included.
Members with no IBAN or no signed mandate. The screen names them before anything is generated: ring them or collect it another way, but do not lose sight of them.
Mark it as returned on its record. Then it does not count as collected and the member sees it in their own area without you having to explain.