Before anything can be ordered that is a special order for a customer, they must have paid in full for the item.
This ensures that the customer comes back for the item. If they don’t pay for it and you order it, and the customer never comes back to get it, it’s a waste of your time and the company’s money because the company may have to either stock the item, or at least pay postage on it.
This is different from getting something in on memo to show. A special order is something that we regularly carry that we don’t happen to have in stock that the customer wants, or some watch we have but with a different dial color. The customer knows exactly what he’s getting. That’s why he should be okay with paying in full in advance.