Since 2010, a bank can't charge you an overdraft fee on a one-time debit card purchase or an ATM withdrawal unless you told it to cover those transactions. The rule is called Regulation E, and the permission is an opt-in. That means you had to say yes to it, and you almost certainly did at account opening, in a stack of paper, in about four seconds. If you're not opted in, the card gets declined at the register instead. A declined card costs you nothing.
The fee runs somewhere in the low thirties per item right now. It has moved around. A federal rule would have capped it at $5 starting in 2025, Congress repealed that rule in May of that year, and fees went back up to where they had been before. So the number is not fixed and it is not going down on its own.
The damage comes from the count rather than the size. Four small purchases on a Saturday, against a balance that went negative Friday night, is four separate fees. The coffee is the cheapest thing in the pile.
Way one: revoke the opt-in. Call and say you want overdraft coverage turned off on debit card and ATM transactions. They have to do it. What changes is that your card gets declined when the money isn't there. It feels bad for about ten seconds and it costs nothing.
Way two: link a savings account or a line of credit for overdraft transfer. When checking runs short, the bank pulls from the account you linked. Some banks charge a smaller transfer fee, some charge nothing, and the amount that moves is just the shortfall instead of a flat penalty. Ask which one your bank does before you set it up.
Way three: change accounts. Plenty of credit unions and a growing number of banks run checking accounts with no overdraft fee at all. Some give you a small cushion before anything gets charged. Switching takes a direct deposit form and a week of watching for automatic payments.
Turning off the opt-in doesn't cover everything, though. Checks and recurring automatic payments, meaning the gym charge and the insurance draft, sit outside the rule. Those can still overdraw your account. The bank can pay them and charge an overdraft fee, or bounce them and charge a returned-item fee, which usually costs the same and adds whatever the merchant tacks on. Low-balance text alerts catch most of those, and they're free to turn on.
One more thing to ask about, because it changes the count. Banks post the day's transactions in an order they choose, and some post the largest one first. That drains the balance faster, so more of the small items behind it bounce. You can't negotiate the posting order, but at the end of the day you can find out what it is. It's a good reason to keep a small cushion sitting in checking instead of running the balance to zero on purpose. If that cushion is turning into real savings, where to keep an emergency fund so you don't spend it covers where it should go.