Which one of the following is NOT a purchasing-related problem that might prevent invoice processing?

The option related to having too many staff members in accounts payable is not directly a purchasing-related problem that affects invoice processing. This choice reflects an internal staffing issue rather than a specific barrier related to the purchasing documentation or communication processes.

In the context of invoice processing, having a copy of the purchase order is crucial for verifying that the invoice matches the agreed-upon terms of the purchase. If this document is missing, it can lead to delays and complications in processing the payment. Similarly, if the purchase order has incomplete information, it can result in confusion or erroneous payments, as accounts payable may require full details to process the invoice accurately. Furthermore, if special terms with suppliers are not communicated to accounts payable, it could lead to invoice discrepancies, adversely impacting the relationship with suppliers.

Thus, while staffing levels can affect operational efficiency, they do not directly pertain to the purchasing-related problems that hinder the processing of invoices in the way that documentation and communication issues do.