An invoice was issued in error — can I just delete it?

It is not deleted but voided or corrected. An unpaid invoice can be voided so it is no longer chased or reminded about; an invoice already partly or fully paid is corrected with a credit note for the amount to be reduced.

A credit note records its reason and its author, then adjusts the invoice balance accordingly. If money has to go back to the family, its value lands in the family wallet and can be spent on the next invoice or refunded.