Check 21 (short for Check Clearing for the 21st Century Act) is a federal law that is designed to enable banks and credit unions to handle more checks electronically, which should make check processing faster and more efficient. Prior to Check 21, many financial institutions had to physically move original paper checks from the bank where the checks are deposited to the bank that pays them. This transportation can be inefficient and costly. After Check 21 becomes effective on October 28, 2004, these same financial institutions will be able to accept and present a new scanned and electronically transmitted version of the check called a "substitute check".
Additional information about Check 21 can be found at the Federal Reserve Board Web site.