A C corporation is the standard US corporate form and the default tax treatment for any incorporated company that has not elected S corporation status. It is a fully separate taxpayer: the company files its own return and pays federal corporate income tax on its profits, currently a flat 21 percent, plus any state tax.
Its defining feature is double taxation. Profits are taxed once inside the company, then a second time as dividend tax when after-tax earnings are paid out to shareholders. In return the C corp offers unlimited shareholders, multiple share classes and easy access to venture capital, which is why almost every large or investor-backed US business is one.
Example: a C corp earns 1,000,000 dollars and pays 210,000 dollars in corporate tax; if it then distributes the remaining 790,000 dollars, shareholders pay dividend tax on top, so the same profit is taxed at two levels.
The model mirrors the corporate tax used almost everywhere else: the UK Ltd, German AG or GmbH, and Italian SpA all tax the company first and the owner second. Compare corporate rates internationally with our tax comparison tool.