Check Clearing for the 21st Century Act, or Check 21 was signed into law on October 28, 2003 and became effective October 28, 2004. Check 21 helps to reduce fraud and keeps your account information secure by producing a digital image of a check which is processed electronically.  An important thing to remember with Check 21 is that the check you write is no longer physically transported in order to complete the payment cycle thus dramatically reducing the time it takes for a check to clear your account. You need to make sure you have sufficient funds available in your account before you write a check as checks can now clear within the same day.