How do overdrafts and bounced checks happen?
When you
 write a check,
 withdraw money from an ATM,
 use your debit card to make a purchase, or
 make an automatic bill payment or other electronic payment
for more than the amount in your checking account, you overdraw your account. Your bank (or your savings and loan or credit union) has the choice to either pay the amount or not. If it pays even though you don’t have the money in your account, you may be charged an "overdraft" fee. If your bank returns your check without paying it, you may be charged a "bounced-check," or "nonsufficient funds," fee. And the person or company that you wrote the check to--for example, a store, your landlord, or the phone company--may charge you a "returned-check" fee in addition to the fee your bank charges you.