Some social workers require licenses certifying that they've been tested on the knowledge and skills needed to practice in the field. Licensure (sometimes called "registration") varies by state and by the type of social work practiced. All states require clinical social workers to hold licenses because these practitioners provide important mental health services. To qualify for clinical licensure, an individual must have a master's in social work (MSW) degree and at least two years of post-degree fieldwork experience. Other types of social workers — such as those in administration, justice and corrections, advocacy, and schools — may not need licensure. Students should check the requirements for their jurisdiction on the Association of Social Work Boards (ASWB) website. This organization administers licensing exams throughout the U.S. and Canada.