When an unpaid invoice no longer needs to be paid (for instance, if a member quit), the invoice can be fully credited. When an invoice is credited, the invoice amount is set to zero and will disappear from the list of open invoices.
The member is no longer able to pay the invoice and will no longer receive any messages.
To credit an invoice, find the invoice in ClubCollect. At the top of the invoice you will find several blue buttons, one of which is “Credit invoice”. This credits the full amount of the invoice.