If you value your customers, you must treat them honorably. You want them to stay with you through the years so do not treat them shabbily. This includes reaching agreement on pricing and payment terms. This involves finding exceptions and obvious errors noted on their legal documents whether they are high or low, to your advantage or not. Correct customers’ wrong prices on their purchase orders as soon as you get them.
Review purchase order details; correct their errors even in their favor. Review incoming purchase orders and bring errors to the attention of your customer in order to correct the agreement you already had with them. Make sure to tell them they have entered a price that is too high on their purchase order when it is clearly more than you discussed.
Tell them when they pay you too much. You do this each and every time because you do not know if someone is testing your honesty in this relationship. You cannot afford to lie to vendors upon which you rely. You want them around for a long time so treat them respectfully.
Tell your vendors if they mistakenly bill at prices lower as well as higher than those negotiated on the purchase order. Be honest and let them know when prices are higher on their purchase order than what you quoted so that you can demonstrate you have integrity and are a reputable firm with which to deal. You are interested in making a profit the honorable way and not in any devious manner. All this sounds pompous but proves to your vendors you are the ideal company for which to work and do their best. Continually prove this trait and you will have very loyal vendors for a very long time, a great idea that helps your bottom line.