The big four accounting firms and other tax shelter promoters came under fire from the IRS, the Treasury Department and Congress for their roles in developing and marketing questionable tax shelters during the 1990s. Here's a closer look at interviews, documents and the statements of company executives that offer more insight into the activities of one promoter, the accounting firm KPMG.

German cities and towns have profited for at least 10 years from complicated financing transactions known as "cross-border leasing" deals that involve the leasing of German assets by U.S. investors. City accountants in Germany have cashed in hundreds of millions of dollars for leasing their streetcars, purification plants, sewage systems, town halls, and school buildings. No one knows exactly how many millions American investors have paid. But since the spring of 2003, the complicated transactions have come under increasing public scrutiny of their legal and ethical implications.

A look at why the Cayman Islands has been called a tax haven, how the island defends itself, and what reforms the international community has proposed.