Consider a customer as a vendor also. A potential customer will sit up and notice very quickly if you not only ask for a purchase order for sales but give him a purchase order to buy from him. Inform purchasing of all new customers because they might qualify as an alternative vendor. Every time your sales department targets a new customer, notify your purchasing department. Your firm needs to evaluate the possibility of buying from that new customer also since the arrangement for both parties may be more than beneficial. Your sales person will be able to solidify his sales pitch if his organization will also be buying products or services. Once you begin selling and buying from the same firm, you force that customer/vendor to think twice before dropping you as their supplier/vendor. They may stop before hurting their own wallet. You also must give very competitive pricing if you expect the best quotes on purchases.