Billing schemes are frauds in which an employee causes the victim organization to issue fraudulent payments by submitting invoices for nonexistent goods or services, inflated invoices, or invoices for personal items. One type of billing scheme uses a shell company that is set up for the purpose of committing the fraud. The shell company is often nothing more than a fake corporate name and a post-office mailbox.

What are some of the ways that shell company invoices can be detected?