Mary Alice Belov planned to put gas in her car, then buy groceries. What she didn’t plan on was the $10 gas purchase freezing $50 of her bank account and forcing Belov, a small-business owner from Goldendale, Wash., to put items from her cart back on the shelf. Blame the all too common "debit hold."

Banks may put a hold on an account when they’ve given the green light to use the card for a purchase whose final amount is unknown. That’s exactly what happens thousands of times a day at gas pumps across the country. You swipe your debit card, the gas station asks your bank for approval, and along with saying yes, the bank may freeze up to $75 of your money for several days, no matter how little gas you buy. That debit hold can put you into the red if you don’t keep much money in your account.