There are many adequate replies to this already, but I'll go so far as to add that the entire electronic banking system is flawed, at least in the US. There is no careful management and validation of authorizations like most people want to imagine. A party interested in withdrawing money from your account needs only your account number and your bank's routing number to do so. Misuse of this is discouraged mostly by the difficulty of doing it anonymously... Which isn't so much of a concern to a corporation you've been allowing to dip into your account already. They'll merely say "it's legitimate" and the bank will tell you to deal with them. There are no protections like those afforded to credit card users. It's been well over a decade ago now, but I once left a job in a blow-up argument and was "unpaid" through reversal of a direct deposit that occurred days earlier. When I spoke to my bank manager, she basically told me "tough luck". Sure, I could have contacted a lawyer, etc, but the point isn't that I didn't have recourse; It's that the system is broken if anyone, at any time, can cause you rack-up a series of $30 NSF charges and keep you from paying your bills for days or weeks.