The fees charged by a bank or financial institution when a customer makes a withdrawal from a checking account that exceeds the available balance. The fees are imposed to cover the cost of the transaction and vary by financial institution. But they can be incurred for each transaction that goes over the available balance and $35 is a typical amount. The Credit Card Accountability, Responsibility and Disclosure Act of 2009 only allows banks to charge overdraft fees if customers “opt in” for overdraft protection. Customers who opt out of that service will simply have any purchase or ATM withdrawal that exceeds their available balance declined at no cost to them.