Corporate Tax Expenditures Are Huge

Estimated corporate revenue losses in 2011, which totaled $181.4 billion, were approximately the same size as the amount of corporate income tax revenue the federal government collected that year.
 

The GAO via the Tax Profs Blog.

Accelerated depreciation accounts for 42% of corporate tax expenditures. 

Another 26% comes from the deferral of income from controlled foreign corporations and financial firms with overseas income.  The 5% of corporate tax expenditure due to the U.S. production deduction which is a deduction on U.S. production activities meant to discourage off shoring, is a further loss of U.S. tax revenues that to a great extent exists simply to counterbalance the other tax expenditure incentives in the other direction.

Three other big tax expenditures for corporations are the R&D tax credit (5%), the low income housing tax credit (3%), and the exclusion of interest on state and local public purpose bonds from income taxation (4%). 

Other smaller corporate tax expenditures account for 20% of the total.

On the flip side, it is worth recalling that one of the most important biases against earned income in the individual income tax code (which also applies to pass through entities) is preferrential treatment for capital gains income.

This is telling.  The main reason to favor capital gains is to encourage productive business investment, but the entities that make the vast majority of productive business investment in the United States don't get this tax break.