As the report says, "The most serious problem facing taxpayers--and the IRS--is the complexity of the Internal Revenue Code."
Olsen estimates that individuals and businesses spend 6.1 billion hours preparing their returns. That equal to a year's labor by three million full-time workers. Individual taxpayers are so befuddled by the Code that she reports 89 percent either pay a preparer or buy commercial software to help with the paperwork. The total cost of compliance in 2008, Olsen estimates, was $163 billion, or more than 11 percent of total income tax collections.
via Megan McArdle.