This Salon article has graphs showing the steady decline in percentage of profits paid as taxes by U.S. corporations. Indeed some large companies pay no taxes.
In 2010 the Verizon company posted a profit of 12 billion. According to the income tax rates of 35 per cent Verizon should have a tax bill of about 4.2 billion. But actually according to figures of the Center for Tax justice the company had a negative tax liability of 703 million. See this article.
The decline in corporate tax started in the 1950's and has been in a downward trend ever since except that it has rebounded a little since the last recession. The nineteen fifties were a period when a great many entered the middle class. Now with taxes much lower on corporations the middle class is fast disappearing. Instead of the tax savings trickling down no doubt they are trickling up to the one per cent!