Banks, of course, aren’t giving up those revenues without a fight. Instead, industry leaders like Bank of America Corp., Wells Fargo & Co., HSBC Holdings PLC’s HSBC North America, Fifth Third Bancorp and others are experimenting with new ways to nick their customers, from imposing maintenance fees on checking accounts to rolling out new charges for services like fraud alerts, debit cards and credit reports.

Making matters trickier, while the banks must disclose the new fees fully, they likely will do so only in the ordinary-looking correspondence that most consumers toss in the trash without reading. The result: Many people will learn of the new charges only after opening their monthly statements.

“You’ve got to read those annoying messages that you get because they will be the ones that will tell you what is happening, so you can be prepared to vote with your checkbook and take it somewhere else,” says Gail Hillebrand, a senior attorney at Consumers Union in San Francisco.

Consumer advocates worry that the new fees will unfairly whack consumers who keep low balances and manage their accounts responsibly to avoid any penalty fees.

“That’s the group that will be most penalized in this environment,” says Bill Handel, vice president of research and product development at Raddon Financial Group, which advises banks and is a unit of Open Solutions Inc.

The first and biggest casualty in the new fee assault: free checking. Most consumers haven’t paid for a checking account in years; banks have long given away their checking services to establish relationships with customers who might later take out a mortgage, invest in one of their mutual funds or otherwise give them more business. Such free accounts have often included other popular—and valuable—perks, such as free online bill payment, debit-card rewards and free check printing.

But, “that is going to change in the next six to 12 months, and there may be some surprises,” says Greg McBride, a senior financial analyst at Bankrate.com.

Banking executives and analysts say the new world of checking is likely to resemble the cable-television industry, where customers pay one amount for bare-bones service and then can load on additional options, such as cash-back programs.

Some bank customers already are getting a sense of what is coming. In recent weeks, HSBC North America has told customers that it is converting their free checking accounts to ones that carry a monthly maintenance fee of up to $15.

Wells Fargo, one of the nation’s largest consumer banks, is eliminating free checking on July 1. Bank of America, the largest U.S. bank as measured by assets, is testing new tiered checking accounts that will encourage customers to increase their activity with the bank. TCF Financial Corp., a Wayzata, Minn.-based bank that built its reputation on the slogan “totally free checking” for 24 years, began charging its customers earlier this year.

Some banks that once waived monthly maintenance fees on checking accounts for people who carried big balances no longer do so or are raising the balance limits. The fees, which run as high as $15, are likely to rise, too.

While some banks will waive the maintenance fee, their lists of requirements are getting longer. HSBC requires customers to maintain a minimum balance or pay a monthly maintenance fee of $8 to $50 a month, depending on the type of account.

An HSBC spokesman said that most of the bank’s customers will avoid paying maintenance fees as long as they continue to comply with the terms. HSBC also is waiving fees for six months for customers who are being moved out of free checking accounts.

Fifth Third Bancorp in Cincinnati, which dropped free checking last fall, now gives customers a handful of ways to avoid a $15 monthly fee, ranging from monthly direct deposit of $100 or more to a combination of five other activities that include debit-card purchases and online bill payment.

A Fifth Third spokeswoman says the bank has introduced multiple accounts to meet the different needs of its customers, and that the company’s bankers work with those customers to help determine the most appropriate account for them.

The details may differ, but banks share a common motivation: They “are trying to figure out how to get paid for checking in ways that aren’t obvious to the customer,” says Kelly Trammell, a managing director at Sheshunoff Consulting & Solutions, an Austin, Texas-based company that advises banks on technology, strategy and other issues. Mr. Trammell says one of his clients is testing an account that would include a $25 monthly maintenance fee for a large number of services. He declined to identify the bank.

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