An accounts payable system in which invoices submitted by electronic data interchange (EDI) are audited for duplicate invoices prior to them being entered into the production database, or environment. Pre-processor logic audits, identifies and returns electronically duplicate transmissions. At this pre-processor level, all inbound invoices are sorted in credit/debit sequence. Invoices are posted (committed to the production accounts payable environment; that is, to the accounts payable data base) one at a time so purchase order history is current for each evaluation. Inbound invoices are sorted by credit/debit. Only debits are audited.