I could see a coherent tax code that taxes corporations, but not individuals, or one that taxed individuals, but not corporations (Of course with either of these there would no doubt be all sorts of new loopholes to deal with). But taxing both seems odd to me.
In Australia, my company gets taxed at a flat 30% on all profits in a year. If I want to take cash out of the company after that tax has been taken, I pay "top-up" tax that brings the total tax paid to the level of my income tax rate.
For example, if the company earned $10000, after all expenses, then it would pay $3000 in tax, leaving $7000 left that I can take out. If I earned no money in the year, my income tax rate is 0%, so the top-up tax is -$3000 (I.e. I get a tax refund for $3000). If I earned $50000 in the year, then my income tax rate is 32.5%, so I would have to pay top-up tax of $250 (I.e. 2.5% of the original $10000, which has already been taxed 30%).
Double taxation shouldn't happen, and while my company was set up for tax minimisation purposes, international corporations are able to do an insane level of fuckery to avoid almost all taxation.
1: http://assets.amuniversal.com/921b06d016420130ff2c001dd8b71c...
http://www.irs.gov/Individuals/Sales-Tax-Deduction-Calculato...
Taxing corporate profits directly at all only accomplishes the following things:
* The profits that are redistributed to shareholders end up being double-taxed; the corporation pays tax on them, and then distributes them to shareholders who pay income tax on them.
* The profits that are reinvested end up being taxed, which reduces the amount that the corporation can reinvest. This directly reduces economic activity, since reinvestment often manifests itself in things like hiring and construction; in other words, increased economic activity. In practice, it might be possible to avoid taxes on these reinvestment activities by accounting for them as expenses and saying, "I guess we didn't make any profit this quarter".
* The profits that are held as cash are taxed, and this isn't actually as big of a deal unless the company is building up a massive stockpile to reinvest later, but in this case it would be fairer to just tax a corporation's cash holdings directly. This would also incentivize corporations to either reinvest their profits or distribute them as dividends, either of which is better for the economy as a whole.