WASHINGTON —  People using offshore credit cards to hide income and evade U.S. taxes can avoid criminal charges if they come forward by April 15, the Internal Revenue Service said Tuesday.

Those cardholders still must pay back taxes, interest and penalties and will have to reveal the promoters and administrators of the credit card accounts. But they won't face civil or criminal charges, such as fraud.

"It's time for those involved in abusive avoidance schemes to make things right," acting IRS Commissioner Bob Wenzel said.

People who solicited or promoted the arrangements won't be given amnesty, he said.

After April 15, the IRS plans to pursue account holders and promoters aggressively with laws that carry prison sentences of up to 20 years.

"Those who misused offshore credit and other payment cards will be able to pay their fair share," Wenzel said. "Just as importantly, it will help the IRS get the people promoting these deals."

The foreign cards and accounts are legal. However, the law requires taxpayers to report them and to pay taxes on the income.

Bank secrecy laws in 30 tax-haven countries have enabled people to hide large incomes and evade U.S. taxes, while living lavishly with their plastic, the IRS said.

The government originally estimated that 1 million U.S. taxpayers hold undisclosed credit cards from offshore banks. Now investigators think fewer people have the accounts, though they do not have a new estimate.

The IRS began obtaining records in 2000 from Visa, MasterCard and American Express to target people for audits and prosecution for tax evasion. The IRS is looking at about 1,000 accounts, some held by prominent and famous Americans, congressional sources said Monday.

The investigation is among the largest ever to target the use of offshore bank accounts to hide income that should be subject to U.S. income taxes.

"I think this is an opportunity for a fresh start that taxpayers would be smart to embrace," said Sen. Charles Grassley, R-Iowa, chairman of the Senate Finance Committee, which oversees the IRS.

As part of the new initiative, the IRS also will closely watch the filing of amended tax returns. Taxpayers attempting to disclose their offshore income this way still will be prosecuted, IRS officials said.

For more information, call (215) 516-3537. That number is not toll-free. E-mail questions should be sent to VCIirs.gov.