A taxation principle referring to income taxes that are paid twice on the same source of earned income.

Double taxation occurs because corporations are considered separate legal entities from their shareholders. As such, corporations pay taxes on their annual earnings, just as individuals do. When corporations pay out dividends to shareholders, those dividend payments incur income-tax liabilities for the shareholders who receive them, even though the earnings that provided the cash to pay the dividends were already taxed at the corporate level.

The concept of double taxation on dividends paid to shareholders has prompted significant debate. While some argue that taxing dividends received by shareholders is an unfair double taxation of income (because it was already taxed at the corporate level), others contend that this tax structure is fair.

Proponents of keeping the "double taxation" on dividends point out that without taxes on dividends, wealthy individuals could enjoy a good living off the dividends they received from owning large amounts of common stock, yet pay essentially zero taxes on their personal income. As well, supporters of dividend taxation point out that dividend payments are voluntary actions by companies and, as such, they are not required to have their income "double taxed" unless they choose to make dividend payments to shareholders.