NEW YORK (AP) — The math is alarming for anyone with a debit card.

At Bank of America, overdrawing your account by as little as $6 could trigger a $35 penalty. If you don't realize you have a negative balance and continue spending, you could incur that fee as many as 10 times in a single day, for a total of $350.

Failing to repay the overdraft within a few days now results in an additional $35 penalty.

When the damage is done, you've racked up fees approaching $400 in less than a week, for overdrawing your account by as little as $60.

It's a worst case scenario, but not entirely far fetched.

While debit cards aren't the only way to incur overdraft fees on checking accounts, they present a particular liability since most people assume they can't spend more than the balance of their checking account, said Kathleen Day, a spokeswoman for the Center for Responsible Lending, an advocacy group based in Durham, N.C.

That was the case just a few years ago, when most banks rejected debit card transactions if there wasn't enough money in the account, said Jean Fox, director of financial services at the Consumer Federation of America.

"If you didn't have enough money, the bank wouldn't accept it and you wouldn't owe anyone a fee," Fox said.

Now automatic enrollment in overdraft programs, which allow consumers to draw more than what's in their accounts, is an industry standard.

Consumer advocates, who have long criticized the practice, note that some banks are even raising overdraft fees.

In February, Bank of America changed its policy to charge $35 for the first overdraft in a 12-month period, up from the previous $25. It also raised to 10 the number of times a day an overdraft fee could be charged, up from the previous five.

Then last month, the North Carolina-based bank instituted a second $35 fee for overdrafts that weren't paid off within five days.

"I always thought the whole purpose of a debit card was that if you had $10 and tried to charge $11, they would deny you. That wasn't the case. It completely defies logic," said Peter Mojica, a 46-year-old software consultant whose son was recently charged fees totaling more than $100 after overdrawing his account by just $2.

PNC Financial, meanwhile, recently raised its fees on overdrafts that weren't paid off from $6 a day to $7 a day for a maximum of $35 over five days. Initial overdraft fees range from $31 to $36, depending on how many times an account was overdrawn in a one-year period.

Chase, which says it hasn't raised its fees recently, also has a tiered system of fees between $25 and $35. The Federal Deposit Insurance Corp. says a 2006 survey found three-quarters of large banks have automated overdraft programs. Citi notes that it does not have an overdraft program; the bank denies debit card transactions if there isn't enough money in an account.

What's particularly troubling about overdraft fees for consumer groups is that debit cards are fast becoming the plastic of choice among U.S. households. The trend has picked up pace amid a slowing economy, as consumers shift from credit cards to debit cards as a way to control spending.

After the recession began in late 2007, executives at Mastercard and Visa noted that greater debit card use was offsetting slowing growth rates for credit cards.

Yet many may not realize they can still spend more than they have with debit cards. It could be a pricey lesson for consumers, as account balances dwindle in the downturn and leave little room for bookkeeping errors, said Fox of CFA, which is based in Washington, D.C.

Overdraft programs on debit cards are often compared to the much-criticized over-the-limit programs for credit cards, which charge consumers for spending beyond their credit limit. Come February, the recently signed credit card law will require banks to give cardholders the choice to opt into such programs. The law doesn't address debit cards, however, and banks can still automatically enroll cardholders into overdraft programs.

According to a survey by CFA conducted in March, initial overdraft fees at banks range from $16 to $36. The median top fee charged is $35 per transaction, regardless of how much is overdrawn, the survey found.

Some banks also charge sustained fees if consumers fail to bring their accounts up to balance with a couple days; CFA says 10 of the 16 largest banks make such assessments.

"The fees can be applied even before consumers know their account is overdrawn," Fox said.

Fees on an array of banking services have been climbing steadily for the past several years. But it's no coincidence that recent hikes on overdraft fees come as new credit card reforms are set to take effect in February.

"This isn't some new phenomenon," Fox said. "But it stands to reason that in tough financial times, the existing customer base is an attractive place to boost profits."

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.