Bank of America Corp. and other banks are preparing new fees on basic banking services as they try to replace revenue lost to regulatory rules, in a push that is expected to spell an end to free checking accounts for many Americans. Free checking accounts, which have been widely available for more than a decade, have been a boon to middle-class consumers and attracted low-income customers to the banking system for the first time. Customers will likely be required to pay new monthly maintenance fees on the most basic accounts that don't generate a lot of activity. To avoid a fee, customers will have to maintain certain account balances or frequently use other banking services, such as credit and debit cards, automated teller machines and online accounts. Some consumer advocates warn the new fees will whack consumers who now manage their bank accounts to avoid such charges. The transformation of checking accounts comes at a time when banks are bouncing back from the steepest financial losses in a generation and are facing new regulations. To accelerate that recovery and recoup losses from new banking rules, financial institutions are increasingly leaning on customers who don't now generate enough revenue for the bank.