There are two kinds of purchase orders that can be processed by Data Archive, Simple POs that are not matched to an invoice and POs that are matched to an invoice. The Simple POs entity only archives and purges invoices that are not matched to an invoice. However, during the Candidate Generation phase, Data Archive does not make the distinction between matched and non-matched POs when initially selecting candidates. This distinction between matched and non-matched POs is made by this “rule,” which flags POs as matched to an invoice.