A minimum account balance is the lowest dollar amount a financial institution requires you to maintain in an account to avoid fees, earn interest, or keep the account open. Checking and savings accounts often require a minimum balance to waive monthly maintenance fees, while investment and brokerage accounts may require a minimum to open or access certain services. Falling below the required balance can trigger fees that quietly erode your savings over time. Understanding the minimum balance requirements of any account you open helps you avoid unnecessary charges.