HACKENSACK, N.J. — Free checking, if it ever was, soon won’t be.

The popular bank accounts with no minimum balance requirements and no regular maintenance fees have been the industry standard for years. But some banks are adding fees as they adapt to federal restrictions on consumer overdraft charges and anticipated caps on interchange, or debit card “swipe fees,” paid by merchants.

A provision in the new financial regulations, which President Barack Obama signed Wednesday, gives the Federal Reserve power to restrict swipe fees. Bankers expect that a new, independent consumer financial protection agency within the Fed, also part of the reform package, may impose further restrictions.

The nation’s largest banks have come to rely heavily on penalty-fee income from free checking accounts. The fees come from out-of-network ATM use, bounced-check fees and other penalties.

Overdraft fees on ATM withdrawals and debit-card purchases have been particularly lucrative for banks, generating $18 billion to $23 billion, according to a study by Novantas LLC, a New York consulting firm, and Informa Research Services. These fees typically range from $20 to $35 per transaction.

But as bank customers complained to lawmakers that they were given an expensive service they did not ask for, some elected officials began clamoring for new restrictions and better disclosure of fees and policies.

The Federal Reserve — smarting from criticism that it failed to rein in risky lending and provide adequate consumer protections leading up to the financial crisis — in November issued changes to its so-called Regulation E, requiring the following:

Consumers must opt in to a bank’s overdraft service for ATM and debit-card transactions before fees can be assessed. Consumers have an “ongoing right” to opt out later on. Financial institutions are prohibited from requiring that consumers opt into ATM and debit card overdraft service in order to get the bank to cover overdrafts for checks and other transactions. Those who do not opt in must be given the same account terms, conditions prices and features as those who do.