While many businesses were, in the past, run on handshakes with customers and suppliers, it is essential today that that these agreements be put to writing. Certainly, not everything needs to be set forth in a detailed writing. Very simple, even handwritten agreements, can be used for many day-to-day items. For instance, a purchase can be documented simply by a written purchase order, detailing the essentials of the transaction, signed by both parties. In this way, disputes as to quantity, price, and delivery dates can be avoided. A simple engagement letter can be used by the company to hire services from other firms. Oftentimes, simply having a transaction documented in writing will often serve to avoid problems that might otherwise occur.