Just to give you an idea - client has 2 divisions who both post invoices daily in at least 2 batches entered by 2 different people. Since Nov 18, one division had 11 batches with errors, the other had 12. Some batches had only 1 invoice wrong, but some batches had more than 1 invoice that double posted. It's a bitch to find them, since they also may have similar parts on the same invoice with the same qty and price and cost, so you can't assume that if you see the same posting twice, it's an error.