All Corporations would have to pay tax at their regular rate on net profit regardless of whether they are from capital gains, long term or short term or regular income, passive or earned.
The Corporate tax rate structure is at a graduated level and is currently at 15% for the first $50,000 of net profit. Thus, for a corporation that is at the 15% tax rate, if it has any capital gains, these gains would be combined with any other income either passive or earned. Now, if the net income does not exceed the $50,000 net profit level would also be taxed at 15%. If it exceeds $50,000 the excess amount would be taxed at the next graduated tax rate of 25% and so on.
The IRS has special rules for treating situations where capital losses exceed capital gains in a regular C corporations. These rules state that the capital losses incurred by a C corporation can only be used to offset capital gains, but not the ordinary income.
Furthermore, whenever capital losses are not used in the current year, they are first carried back three years and used to offset capital gains, if any, in those years.
To the extent capital losses are not used in the carry back years, they can only be carried forward five years. If not used in the carry back or carry forward period, the capital losses would expire!