That is a reader request. I used to think the ideal tax rate on corporations should be zero, but that is no longer my view. For one thing, too many individuals would find ways to self-incorporate, thereby avoiding personal income taxes on labor income. Note that a small corporation controlled by you can return real income to you in a variety of non-taxable or less-taxed ways.
Furthermore, tax-exempt institutions such as non-profits and pension fund would end up owning too many corporations, to the detriment of (non-tax) efficiency. While pension funds eventually must pay out that income in the form of pensions, those often go to high-wealth, low income elderly individuals, and thus would never end up taxed at such a high rate.
I now think that for the United States the tax rate on corporate income should be in the range of 18-25 percent, depending of course on what other decisions we make with our budget and tax systems. It also would work to simply target the OECD average of the corporate rate.
A further question is whether the case for a zero corporate rate would be stronger if we shifted from income to consumption taxation. That depends how easy it might be to partially evade the consumption tax, say by spending money abroad. In general, to the extent evasion is possible that favors lower marginal tax rates but levied on a greater number of distinct points in the system, including in this case on the corporate veil.
I thank Megan McArdle for a useful conversation related to these points.