The "bogus order" fraud.
This nasty little trick can not only cost you a fair whack, it may also damage your relationship with your customer as you try to blame others for your mishap.
How it works: The crook will phone through an order for your goods pretending to be a buyer from one of your existing customers. He will use some excuse to have the goods delivered to a different location (Eg: please deliver directly to our construction site / directly to our customer at...) or will arrange to have the goods collected from your premises. Like a good supplier you do as you are told to make life easy for your valued customer. However when it comes time for payment, your real customer knows nothing about the phantom order and of course doesn't pay for it. In the mean time the crook has had plenty of time to disappear with your goods and chances are you have no idea who it was.
How to prevent it: 1) Know your customers. If there is a new voice placing an order, phone back to confirm something on the order. 2) Whenever goods are collected, write down the vehicle registration number on your copy of the delivery note or invoice. 3) Always confirm large orders with you customer. Phone simply to thank them if you have to, but find a way to check they know about it even if it has been faxed or emailed.