(Reuters) - A powerful U.S. Senate panel on Thursday will examine the tax implications of how U.S. multinational corporations shift overseas profits around the world.

The Senate's Permanent Subcommittee on Investigations put out some details about the hearing on Tuesday. The panel said it will focus on the "shifting of profits offshore by U.S. multinational corporations" and U.S. tax law.

The committee said witnesses will include tax executives from Microsoft Corp and Hewlett-Packard Co; a tax executive from Big Four accounting firm Ernst & Young; and senior officials from the U.S. Internal Revenue Service.

Democratic Senator Carl Levin, who chairs the panel, has been investigating offshore tax evasion for years and frequently issues voluminous reports calling attention to the issue.

Further details of the latest findings by Levin's committee were not being disclosed by the panel.

"The focus of the hearing is money coming back into the U.S. within the businesses of the companies that claim to have it permanently reinvested offshore," said a person briefed on the hearing's agenda who asked not to be identified.

Multinationals have amassed up to $1.5 trillion in profits overseas and say that bringing that money into the United States, or repatriating it, is too costly because the profits would be taxed at 35 percent. Keeping the profits overseas allows the corporations to defer U.S. taxes owed on them.

Many corporations say their offshore funds are "permanently reinvested" overseas due to the high U.S. tax. But billions of these offshore dollars quietly make their way into the United States when the companies' foreign units lend money to U.S. entities, said the person briefed on the agenda.

(Reporting by Lynnley Browning; Additional reporting by Kim Dixon; Editing by Kevin Drawbaugh and Leslie Adler)