Here are details on the scandal from an editorial published at CNN.com, by Peter C. Canellos, a lawyer, is former chair of the New York State Bar Association Tax Section. Edward D. Kleinbard is a professor at Gould School of Law at the University of Southern California. He is the former chief of staff of Congress’s Joint Committee on Taxation:

Romney has had a close, long-standing, personal and business connection with Marriott International and its founders. He served as a member of the Marriott board of directors for many years. From 1993 to 1998, Romney was the head of the audit committee of the Marriott board.

During that period, Marriott engaged in a series of complex and high-profile maneuvers, including “Son of Boss,” a notoriously abusive prepackaged tax shelter that investment banks and accounting firms marketed to corporations such as Marriott. In this respect, Marriott was in the vanguard of a then-emerging corporate tax shelter bubble that substantially undermined the entire corporate tax system.

Son of Boss and its related shelters represented perhaps the largest tax avoidance scheme in history, costing the U.S. many billions in lost corporate tax revenues. In response, the government initiated legal challenges that resulted in complete disallowance of the losses claimed by Marriott and other corporations.

In addition, the Son of Boss transaction was listed by the Internal Revenue Service as an abusive transaction, requiring specific disclosure and subject to heavy penalties. Statutory penalties were also made more stringent to deter future tax shelter activity. Finally, the government brought successful criminal prosecutions against a number of individuals involved in Son of Boss and related transactions not associated with Marriott, including principals at major law and accounting firms.

In his key role as chairman of the Marriott board’s audit committee, Romney approved the firm’s reporting of fictional tax losses exceeding $70 million generated by its Son of Boss transaction. His endorsement of this stratagem provides insight into Romney’s professional ethics and attitude toward tax compliance obligations.

Hat tip: Paula in the Comments and The Dish.