Post secondary education—especially a bachelor's degree—is recommended, but not required, for entry-level positions in interior design. 3 States plus the District of Columbia, and Puerto Rico license interior designers and 19 states certify or register interior designers. Following formal training, graduates may enter a 1-year to 3-year apprenticeship to gain experience before taking a national licensing exam or joining a professional association. Designers in States that do not require the exam may opt to take it as proof of their qualifications. The National Council for Interior Design Qualification (NCIDQ) administers the licensing exam. To be eligible to take the exam, applicants must have at least 6 years of combined education and experience in interior design, of which at least 2 years constitute post secondary education in design. Once candidates have passed the qualifying exam, they are granted the title of Certified, Registered, or Licensed Interior Designer, depending on the state. Some states require continuing education units in order to maintain one's license.