Microcap stock fraud is a form of securities fraud involving stocks of "microcap" companies, generally defined in the United States as those with a market capitalization of under $250 million. Its prevalence has been estimated to run into the billions of dollars a year. Many microcap stocks are penny stocks, which the SEC defines as a security that trades at less than $5 per share, is not listed on a national exchange, and fails to meet other specific criteria.