Lenard said in a two-paragraph order that based on the government court filings, "there is a reasonable basis for believing such a group or class of persons may fail or may have failed to comply" with U.S. tax laws.

The summons will allow the IRS to obtain information about American taxpayers who have UBS accounts but did not file required forms detailing their taxable income.

"The order clears the way for the IRS to take the next steps against wealthy individuals who don't pay their taxes," said IRS Commissioner Doug Shulman in a written statement. "People with hidden foreign accounts can no longer rest easy."

UBS has said it is cooperating with Swiss and U.S. investigations and will disclose records involving U.S. clients who might have broken tax laws.

"As we have noted, UBS takes this matter very seriously and is working diligently with both Swiss and U.S. government authorities, consistent with Swiss law and the legal frameworks for intergovernmental cooperation and assistance," UBS said in a statement Tuesday.

U.S. taxpayers are required to report all foreign financial accounts if their total value exceeds $10,000 at any point during a given year, prosecutors said. Failure to report the accounts can result in a penalty of up to 50 percent of the amount in the accounts.

The Justice Department requested the summons after former UBS private banker Bradley Birkenfeld, 43, pleaded guilty in a Florida federal court to defrauding the IRS. Birkenfeld, who is cooperating with investigators, said in court that UBS has about $20 billion in assets in undeclared accounts for U.S. taxpayers.

Prosecutors said Birkenfeld and others helped California billionaire Igor Olenicoff hide $200 million in assets overseas. Olenicoff, who controls a real estate empire, pleaded guilty last year to tax charges and agreed to pay the IRS more than $52 million.