An "S-Corporation" is a regular corporation that has between 1 and 100 shareholders and that passes-through net income or losses to shareholders. An S Corp is a corporation that elects to be treated as a pass-through entity (such as a sole proprietorship or partnership) for tax purposes. Since all corporate income is "passed through" directly to the shareholders who include the income on their individual tax returns, S Corporation are not subject to double taxation.
An eligible domestic corporation can avoid double taxation (once to the shareholders and again to the corporation) by electing to be treated as an S corporation. Generally, an S corporation is exempt from federal income tax other than tax on certain capital gains and passive income. On their tax returns, the S corporation's shareholders include their share of the corporation's separately stated items of income, deduction, loss, and credit, and their share of non-separately stated income or loss.