[August]

Here's who pays what:

In 2002 the latest year of available data, the top 5 percent of taxpayers paid more than one-half (53.8 percent) of all individual income taxes, but reported roughly one-third (30.6 percent) of income.
The top 1 percent of taxpayers paid 33.7 percent of all individual income taxes in 2002. This group of taxpayers has paid more than 30 percent of individual income taxes since 1995. Moreover, since 1990 this group’s tax share has grown faster than their income share.
Taxpayers who rank in the top 50 percent of taxpayers by income pay virtually all individual income taxes. In all years since 1990, taxpayers in this group have paid over 94 percent of all individual income taxes. In 2000, 2001, and 2002, this group paid over 96 percent of the total.

http://usgovinfo.about.com/od/income...hopaysmost.htm