If you had a check that you don't have sufficent funds for that has been run through the bank the bank will usually charge you an overdraft fee. This means that you have arranged an overdraft loan/agreement with the bank. The bank will go ahead and pay the fund to the person or company you wrote the check to. You will have a certain amount of time to put the money back into your account and pay the overdraft fee. Many banks will give you 24 hours to cover the check before they charge you a fee. The fee is usually around $25 dollars, but could be more depending on your bank rules.