Your account becomes negative when the balance goes below zero. It’s also called an overdraft. This occurs when you make payments that you don’t have enough money in the account to cover. If the bank accepts the payment, your account incurs a debt, making your balance negative.

To help you visualise this, imagine you have $500 in your account, and you write a check for $515, because you thought you had a balance of $600. If the bank pays the $515, you end up with an account balance of minus $15. That’s the difference between how much money you had in the account and how much the bank paid the person that cashed your check. As you see, the bank did you a favor by making up the difference.