Differing requirements for CPA certification, reciprocity, temporary practice and other aspects of state accountancy legislation in the 55 U.S. licensing jurisdictions (the 50 states, Puerto Rico, the District of Columbia, the U.S. Virgin Islands, Guam and the Commonwealth of the Northern Mariana Islands) make the interstate practice and mobility of CPAs more complicated. By removing boundaries to practice in the U.S., CPAs are able to more readily serve individuals and businesses in need of their expertise. At the same time, the state board of accountancy's ability to discipline is enhanced by being based on a CPA and the CPA firm's performance of services (either physically, electronically or otherwise within a state), rather than being based on whether a state license is held.