v5.1 Premium. User has three invoices from 11/3 and three credit memos from 11/11 and the three credit memos have the same invoice number as the three invoices. The credit memos do not relate/applied to the invoices. The credit memos are applied to different invoices. Other than someone randomly choosing an invoice number to re-use, how can this happen? Secondly, where is the setting to not allow the re-use of SO invoice numbers? Don't laugh, it is Friday.