Book of business is common parlance in the United States legal services sector and refers to the collection of clients that a lawyer (usually a partner) has assembled throughout his or her career. It is often used to refer to the valuation of such client following. A conflict of interest check is also an important step before a book of business can be considered portable. For example, a partner whose primary clients are insurance policyholders would generally be unable to take most of his book of business to a firm that represents insurers.