Deutsche Bank “overstated” the value of a multibillion-dollar portfolio of sophisticated derivatives during the height of the financial crisis, leading it to file inaccurate financial statements for at least a six-month stretch, securities regulators in the United States said on Tuesday.

The bank, without admitting or denying wrongdoing, agreed to pay a $55 million penalty to the Securities and Exchange Commission to settle claims that its “inadequate internal accounting controls” violated federal securities law.

The settlement closes the door on a five-year investigation into claims raised in part by former Deutsche Bank employees that the bank mispriced assets held in a large portfolio of derivatives to hide potential trading losses in the credit markets during the crisis. The S.E.C. estimated that the bank had overvalued the derivatives portfolio by $1.5 billion.

The settlement is one of the last remaining investigations arising from the crisis and sheds further light on the frantic activities that went on behind the scenes at big banks as they wrestled with the fallout from the collapse of Lehman Brothers in September 2008 and the near-collapse of the American International Group, the giant insurer.