Although most corporate income falls within the 35 percent tax bracket, the average tax rate on corporate income (corporate taxes divided by corporate income) is lower than 35 percent because of allowable deductions, exclusions, tax credits, and the lower tax rates that apply to the first $10 million of income.his option would increase all corporate income tax rates by 1 percentage point. For example, the corporate income tax rate would increase to 36 percent for taxable income above $10 million.