The customer/supplier relationship is no longer a matter of trust and good will. If you've ever been left with unsaleable inventory from a JIT relationship, had your invoices unreasonably aged, or arbitrarily had a shipment rejected for no understandable reason you know how it feels to be treated poorly. The solution to this problem is you having a Policy Manual telling your customers how you do business.
This downloadable version contains two word processor files. One tells you how to modify the manual to develop your own policies. The other is the actual Policy Manual itself. You put in your company's name, make the changes that fit your particular company, and issue it to your customers. By saving just one frivolous reject or unnecessary vendor evaluation visit, this has paid for itself many times over.