The regulations are temporary and may undergo minor changes before being completed. Another proposed regulation would require companies to report to shareholders and the Internal Revenue Service other large transactions in which the shareholders may be subject to tax.

The Bush administration has acknowledged a growing problem involving companies relocating to offshore tax havens.

In what's known as a corporate inversion, a company sets up a shell headquarters in a tax haven such as Bermuda while keeping most operations and jobs in the United States. Such a move often offers potential savings in U.S. taxes of millions of dollars.

Under the new temporary regulations, companies that moved operations this year will be required to complete and furnish to shareholders tax forms reporting gains from the transaction.

Until now, no reporting requirements existed for stock transfers in inversions and other taxable reorganization transactions.

Dozens of U.S. corporations have relocated headquarters to tax havens in recent years, including Tyco International, Fruit of the Loom, Accenture, Ingersoll-Rand and Cooper Industries.

Harken Energy Corp. set up a subsidiary in the Cayman Islands when President Bush was on the company's board of directors. Bush has said he opposed the venture. Tax lawyers have said the Harken arrangement differed from other corporate moves because it did not involve setting up a new parent company that would pay no U.S. taxes on its foreign-earned income.

Also, Halliburton Co., a Dallas-based energy services company, registered at least 20 subsidiaries in the Cayman Islands when Vice President Dick Cheney was chief executive from 1995 to 2000.

On the Net: Treasury release: http://www.ustreas.gov/press/releases/po3612.htm