In the past two years, some of the wealthiest executives in the U.S. have used deals similar to McCombs's to reap returns while deferring the taxes without running afoul of IRS rules, securities filings show.

Dole Food Co. Chairman David H. Murdock received about $228.6 million in 2009 against his Dole shares -- tax-free until he is scheduled to deliver shares in November 2012, a filing shows.

Starr International

Starr International Co., the investment vehicle run by Maurice "Hank" Greenberg -- forced from his position as chairman and chief executive officer of American International Group Inc. in 2005 -- utilized a prepaid forward agreement last year to receive $278.2 million from an investment bank, according to a March 2010 regulatory filing. The investment vehicle isn't slated to deliver the AIG stock until 2013.

Lauder received $72.9 million in June as part of a variable prepaid forward sale and is scheduled to deliver the Estee Lauder Cos. shares in June 2014, according to a filing with the U.S. Securities and Exchange Commission.

Spokespersons for Lauder, Murdock and Starr International declined to comment.

Realized Gains

While the tax treatment of these plans isn't disclosed in the filings, "there's no other reason to enter into such a convoluted arrangement," said Robert Willens, an independent tax accounting analyst in New York. These arrangements can cost several million dollars in fees, according to tax planners.

Taxes on capital gains are triggered when assets like appreciated shares are sold -- a process called realization. What constitutes a realized, taxable sale is a frequent bone of contention between the IRS and the clients of tax planners.

Transactions intended to pull cash out of appreciated assets tax-free aren't limited to stock. Boston real estate developer Arthur M. Winn exited his interest in a piece of real estate by converting his stake into a share of a partnership free of any capital gains tax, court filings show.

The IRS objected and claimed Winn and his partner should have reported a $12 million taxable gain. A U.S. Tax Court judge sided with Winn on one aspect of the deal; others were settled with the government. The details haven't been disclosed.