do underwriters always work for investment banks 
underwriters are responsible for assessing risk during financial transactions and deciding whether they or the company they work for will assume that risk investment banks are one type of company that employs underwriters insurers and other financial institutions also employ underwriters the entire underwriting department of an investment bank can serve as book runner the bottom linea book runner is the primary underwriter when an investment bank issues new equity debt or securities instruments they are the lead underwriting firm that runs or is in charge of the books for example during an ipo the book runner usually works with other investment banks to establish an underwriter syndicate thereby creating the initial sales force for shares this reduces risk but also decreases the share of profit that each part of the syndicate makes however because the book runner takes on the most responsibility during the offering they also usually get the highest commission from the transaction 