Overdraft protection is a service offered by banks and credit unions that allows customers to link their checking account to another account, such as a savings account or line of credit. If the customer makes transactions that exceed the balance in their checking account, the bank will draw on the linked account to cover the overdraft, up to an agreed-upon limit. This prevents bounced checks and fees associated with insufficient funds. The customer typically pays a fee for this service, as well as interest on any money borrowed through overdraft protection.