Do I need a CPA in all states to work as an investment underwriter?

You do need to take several exams to get a CPA which include Series 7 and series 66. The exams are offered by the Financial Industry Regulatory Authority . You have to have at least 4 months of work at a firm to be eligible to take the exams. There is really nothing that says that you need to have a CPA in all states. One would do and you should be able to work anywhere that you choose. Also choosing to internship may help.