The advertisement from Capital One had many of the same promises that other banks offer for high-yield savings accounts: There were no fees, no minimum deposits and the money would earn much more in interest than in traditional bank accounts.
“What’s the catch? There is none,” the bank boasted.
But, according to a lawsuit filed against Capital One on Tuesday by the Consumer Financial Protection Bureau, there was one, and it cost depositors more than $2 billion.
For years, Capital One held interests artificially low in the high-yield product, to 0.30 percent annually last summer, for instance, even as the Federal Reserve raised rates above 5 percent.
Banks are generally permitted to pay as little in interest as their customers will permit, but Capital One went too far, according to the lawsuit, by deliberately confusing its customers about its products. The bank operated two separate, nearly identically named account options — 360 Savings and 360 Performance Savings — and forbade its employees from volunteering information about or marketing 360 Performance Savings, the higher-paying one, to existing customers.
In its lawsuit, the C.F.P.B. called the practice deceptive, abusive and illegal. “The only thing that has ever meaningfully distinguished 360 Performance Savings from 360 Savings is the former product’s higher interest rate,” the lawsuit said.
A Capital One spokesman, Sie Soheili, declined to comment on the specific allegations in the suit, but he said the bank, the nation’s ninth largest, disagreed with the claims and would dispute them in court. The bank is trying to complete a deal to acquire the credit-card issuer Discover.
The lawsuit is the latest in a flurry of last-minute admonishments from the C.F.P.B. ahead of the inauguration of President-elect Donald J. Trump. Republicans largely loathe the agency, founded in 2011, which they have said is an example of bureaucratic overreach, though Mr. Trump kept it alive during his first term.
Nearly every working day for the past month, the agency has filed a lawsuit or proposed a rule change or other pending action against a major financial institution. The lawsuit on Tuesday was not the agency’s first in recent weeks involving Capital One; last month, the regulator accused Zelle, the money-transfer app co-owned by the bank, of failing to protect its customers against more than $800 million in fraud.
Mr. Soheili said in a statement that the regulators were continuing their “recent pattern of filing 11th-hour lawsuits ahead of a change in administration.”
A C.F.P.B. spokeswoman, Tia Elbaum, responded: “Where we see violations of the law, we will take action.”
