An overdraft fee is a charge that a bank or financial institution imposes when a customer withdraws more money from their account than is available. This can happen with checks, debit card transactions, or ATM withdrawals. The fee is intended to cover the risk the bank takes when allowing the account to go into a negative balance. Typically, the amount of an overdraft fee can vary by institution, but it often ranges from $30 to $40 per transaction. Customers can avoid these fees by keeping track of their account balance and opting for overdraft protection services, which may link to a savings account or credit line.