Fed and FDIC

As a result, the Federal Reserve passed a rule effective July 1, 2010, requiring banks to obtain an "opt-in" from customers for overdraft protection on debit and ATM transactions. After market research on what would benefit consumers, the Fed didn't cover paper checks or electronic transfers.

That same year, the Federal Deposit Insurance Corp. required the banks it supervised to counsel customers who use frequent overdrafts about alternate ways to manage their money. The Office of the Comptroller of the Currency proposed its own guidance, which would cover national banks such as JPMorgan or Wells, last year.

It's unclear how the rules have affected enrollment. Moebs estimates that 77 percent of bank customers have opted in, while the Consumer Bankers Association concluded in an October study that the rate was 17 percent. The Center for Responsible Lending, a Durham, North Carolina-based advocacy group, estimated the opt-in rate at about 33 percent.

Understanding how many people are signing up may help inform the debate about whether the banks' marketing is deceptive. That's why the consumer bureau hopes to clarify the enrollment rate as part of its inquiry, said the people briefed.

The rule changes in 2010 didn't stop banks from marketing their overdraft programs, which they portray as a consumer benefit, said Susan Wolfe, vice president for Mintel Comperemedia, a London-based consultancy that catalogs marketing materials in financial services.

"The banks are dealing with significant trust and image issues, so they're trying to be seen as a partner," Wolfe said in an interview.

Chase, the retail arm of JPMorgan, warns customers who don't opt for the overdraft protection that they will "need to make sufficient deposits so that everyday debit card purchases will be approved," according to a letter from the bank posted on the website mainstreet.com in February.

Susan Weinstock, director of the Safe Checking in the Electronic Age Project at the Pew Charitable Trusts in Washington, said that marketing has led to consumer confusion.

Pew conducted two focus groups on overdrafts during April 2011 and found that people frequently misconstrued the notion of opting out, Weinstock said.