They send those notices to all sorts of places ;-)

Presumably some of the invoices get paid. CB has mentioned they started sending his to the Accounts Receivable Dept. Presumably they hope that it's more cost-effective for a firm simply to pay a relatively small account than to pursue an employee and dispute the charge.

FWIW, it's amazing what can be missed in a busy accounting department. One time I authorized a shipping bill of $1500 on behalf of a customer and paid it myself by credit card. The customer then received and paid the invoice again, leaving them $1500 in credit with the shipping company, who duly reported this in the next statement. This credit was interpreted as an invoice matching the approved amount, so it was paid again. The shipper's next statement reported a $3000 credit that was sent to me for re-approval since it exceeded the agreed amount. Had I said OK, they would have paid another $3000. In such an environment, a stern Eli invoice may well be assigned against a budget and quietly paid.